# PowerTap Disc



## LyndaW (Jul 22, 2005)

I got one!

Here are pictures of it. I can't ride it today but I'll be on it tomorrow.


----------



## RideToLive (Mar 31, 2007)

*Sweet!*

No excuses for missing training logging now!


----------



## LMN (Sep 8, 2007)

Let me know how the water sealing works.


Power taps and wet haven't exactly worked well in the past. They claim to have fixed it but that remains to be seen.


----------



## William D (Oct 31, 2005)

so these are now available for purchase? awesome. a few weeks ago they said they were still on the production line.....


----------



## Cracked Headtube (Apr 16, 2006)

Saris can't build them fast enough. I work at American Classic, and we are building on them!! If you want a Disc Brake 2.4 Powertap we can build them 26" or 29", 32 hole only. 
LMN- the computer seal is VERY tight on these. We double check every PT we ship to ensure the seal is good. No problems so far for us!


----------



## tomk96 (Nov 10, 2004)

sweet.


----------



## sprocketjockey9 (Jul 18, 2006)

Ordered mine up today....gonna be laced up to a stans ZTR 355 29" rim.

Anyone interested in an ergomo pro??? for sale


----------



## RickySilk (Jan 28, 2007)

sprocketjockey9 said:


> Ordered mine up today....gonna be laced up to a stans ZTR 355 29" rim.


Jason, where did you order from?


----------



## sprocketjockey9 (Jul 18, 2006)

I ordered mine from my local shop: Geneva Bicycle Center, my guess is they called Saris and are able to get one? The shop is going to build it up to the hoop for me


----------



## William D (Oct 31, 2005)

funny, i too just order one and am lacing it to a stans 355 29er wheel....got mine from Rich at prowheelbuilder.com. they said a few weeks delivery....fingers crossed on that.


----------



## Cracked Headtube (Apr 16, 2006)

Saris has the hubs, just no rotors to go with them...I guess they've been selling extra rotors.


----------



## laufer (Jul 11, 2006)

How much $dinero$ ?


----------



## William D (Oct 31, 2005)

i assume any standard rotor will work, yes?? i paid $1500 for mine.


----------



## MightySchmoePong (Jan 12, 2004)

William D said:


> i assume any standard rotor will work, yes?? i paid $1500 for mine.


No, I believe they have a custom bolt pattern.


----------



## LyndaW (Jul 22, 2005)

William D said:


> i assume any standard rotor will work, yes?? i paid $1500 for mine.


Custom rotor. 8 bolt pattern.


----------



## bn_acyclist (Jun 6, 2006)

*Just Received Mine!*

Thanks to American Classic and Red Rock Bicycle Co.


----------



## LyndaW (Jul 22, 2005)

bn_acyclist said:


> Thanks to American Classic and Red Rock Bicycle Co.
> View attachment 356802


awwww she's luvly. We'll have to take them out for a ride together 

Was it plug and play for you or did you have to mess around with a few settings? How do you feel the power readings compare to your other PT's?


----------



## bn_acyclist (Jun 6, 2006)

*Plug and Play.*

Plug and play, I set the time and aranged the display how I like it before I rode. But it worked right out of the box. 
I only have one ride on her but the data I downloaded was perfect. It seemed to have way less if any holes in the data. 
Oh, BTW thanks for the consult. (LWcoaching) A few things that I learned in that informative meeting have led to the best year yet (so far, knock on wood). Thanks.


----------



## Cracked Headtube (Apr 16, 2006)

BN_A could you get me a Disc side photo of your wheel in the bike? A Similar angle to the one above, just from the other side.
[email protected]

thanks


----------



## JustusA (Nov 9, 2007)

Could someone please tell me what the actual weight of the hub with and without rotor is?


----------



## playpunk (Apr 1, 2005)

you can't get the hub w/o the rotor, as far as I know.


----------



## perryr (Jul 26, 2004)

My PT Disk, with a 347g Stans 355 rim, 2.0/1.8 and 2.0/1.5 spokes 3x, Aluminum nips, Yellow tape, weighs 1030 without rotor. Add 160g for custom rotor, and also add for rotor bolts (x8). 

I did not get a chance to weigh the hub, but it looks like it should be very close to a standard PT SL (without rotor of course). You also need to add for the different axle, which I believe is steel.


----------



## Circlip (Mar 29, 2004)

perryr said:


> My PT Disk, with a 347g Stans 355 rim, 2.0/1.8 and 2.0/1.5 spokes 3x, Aluminum nips, Yellow tape, weighs 1030 without rotor. Add 160g for custom rotor, and also add for rotor bolts (x8).
> 
> I did not get a chance to weigh the hub, but it looks like it should be very close to a standard PT SL (without rotor of course). You also need to add for the different axle, which I believe is steel.


That seems dead on based on available info. Alum nips are ~10g per wheel, and the mix of spokes you have is ~165g per wheel. A few grams for the yellow tape, some subtraction, and I get 504g for hub only without rotor or rotor mounting hardware.

Compared to Saris' web info quoting 680g less 160g for rotor as per Perry's post above, and maybe 15g for rotor bolts that gives 505g which is almost a dead match. Saris says the regular (i.e. road) PT 2.4 SL is 416g, so that means about 89g extra for all the extra material on the hub for the rotor mount, and any other changes they needed to maix it suitable for disc/MTB use.


----------



## perryr (Jul 26, 2004)

Circlip said:


> Saris says the regular (i.e. road) PT 2.4 SL is 416g, so that means about 89g extra for all the extra material on the hub for the rotor mount, and any other changes they needed to maix it suitable for disc/MTB use.


I bet most of that 89g is in the steel axle.


----------



## sprocketjockey9 (Jul 18, 2006)

Built and ready to go for testing this afternoon :thumbsup:


----------



## RideToLive (Mar 31, 2007)

*Just about ready*

My special savings account is about there! Did you build yours up yourself Jason? While I love to build, I rarely have the time. I'm considering, PT Disc / Olympics / DT 1.8-1.5 w/ alloy nipples. That way, if I want to race it, I can do so.


----------



## RickySilk (Jan 28, 2007)

Nice. I ordered a wheel two weeks ago but the hub is backordered for a week due to the lack of rotors.


----------



## sprocketjockey9 (Jul 18, 2006)

I wish I could build it up. If I did it probably would come out as a triangle or something....I can do everything 'cept that part.

"stimulus check", just like my taxes.......deposited right at the bike shop

I built mine up a little beefier with the ZTR and brass nipples as it will see some tough miles. I'll still race it, in fact racing it tonight. just not as light as the bonty x lites


----------



## butryon (Aug 12, 2005)

*mtb training w/power*

Jason, LMN, Lynda......whoever,
How does training w/ power differ in the mtns. vs. the road, and what would you suggest doing when first getting started with it? My hub is here just waiting for my hoop to show up and then it's on. Also, any book recommends or site visits to help learn how to train better w/it? 
Thanks,
Ryon


----------



## sprocketjockey9 (Jul 18, 2006)

A great book is Racing and training with a Power meter by Allen and Coggan is a great place to start.

Also http://www.cyclingpeakssoftware.com/power411/ is the lowdown on power training from the same people (the book expands upon these theories).

the first thing I would do with it is to determine your power training zones, on the power411 page is a brief description on how to set up your zones.

The big difference between road and off road power, in my belief comes down to quandrant analysis. While power is power across the board, how you produce it is a little bit different off-road. Unfortunately, a review of this is only available after a workout and not during. Road tends to be high force/high rpm, while mountain biking is high force/low rpm.

With the power meter you can also get "data" proof of your actual weaknesses and target it exactly. Kinda like using a laser sight to hone in on your target, vs blind firing.


----------



## butryon (Aug 12, 2005)

So, last year I tested with my road power tap and got some numbers for a 20 min. test and they were pretty accurate for a twenty min. based on the 4 hill climbs I did. They were plus or minus 10 watts. Are these numbers a good place to start? also, is average power a good indicator of your ride or go by tss. I have limited knowledge here so I am throwing out vocab. stuff w/limted info. sorry
Thanks,
Ryon


----------



## sprocketjockey9 (Jul 18, 2006)

butryon said:


> So, last year I tested with my road power tap and got some numbers for a 20 min. test and they were pretty accurate for a twenty min. based on the 4 hill climbs I did. They were plus or minus 10 watts. Are these numbers a good place to start? also, is average power a good indicator of your ride or go by tss. I have limited knowledge here so I am throwing out vocab. stuff w/limted info. sorry
> Thanks,
> Ryon


You can use those numbers as a start, but I'd still recommend trying to get a real test in. Understandably, it's probably pretty hard to do off-road 20 minute test or so, but just give it your best effort on a section of trail or a road where you can recreate it. I think TSS gives more value to a workout than an avg power number. If you're using wko+ you can use the Performance Chart Manager and track TSS and see how it influences your form and fitness.

If you're really interested in the fine detail of power there is a google group on "wattage".


----------



## butryon (Aug 12, 2005)

Thanks Jason,
As I get going more I will drive you crazy w/ some ?'s following a true dirt 20 min. Should I shoot for a 30 min.?
Thanks again,Ryon


----------



## LyndaW (Jul 22, 2005)

butryon said:


> So, last year I tested with my road power tap and got some numbers for a 20 min. test and they were pretty accurate for a twenty min. based on the 4 hill climbs I did. They were plus or minus 10 watts. Are these numbers a good place to start? also, is average power a good indicator of your ride or go by tss. I have limited knowledge here so I am throwing out vocab. stuff w/limted info. sorry
> Thanks,
> Ryon


I always have my athletes test on the pavement even if they are on their mtb - fewer variables to interrupt the test.

Do a new test to be sure you are setting your power training levels on up-to-date info.

The more technical a course is the lower your mtb FT will be. As you ride on all different types of courses the exact FT to use to calculate TSS for an mtb ride on a daily basis is a bit of guesswork. In general I use an FT 5% lower for mtb rides than the road FT for TSS purposes.

Tracking daily TSS in the Performance Manager Chart is the bomb for training planning and nailing peaks.


----------



## zrm (Oct 11, 2006)

I don't need to spend that kind of moola to get confirmation of what I already know. 

I'm weak.


----------



## sprocketjockey9 (Jul 18, 2006)

butryon said:


> Thanks Jason,
> As I get going more I will drive you crazy w/ some ?'s following a true dirt 20 min. Should I shoot for a 30 min.?
> Thanks again,Ryon


No problem, Once you do your 20 min test (in agreement with Lynda as far as testing on the road vs. dirt) there's no real need to move onto a 30 minute test. 20 minute is the norm and you can just extrapolate your FTP from there. 20 min ~ 95% or so of your FTP


----------



## butryon (Aug 12, 2005)

Lynda and Jason,
So, based on my 20 min. test and three Hillclimbs last year I came up w/ a 20 min. of 333 watts, averageing the 4 rides. that will put my ftp at 316(333*.95) correct? and then expect 5% less than that on dirt = 300.2 watts. 
Based on these numbers where will most of my training for mtb racing be at? I generally only ride the road a few times a month, hence, why I sold my road power tap.
Thanks again,
Ryon


----------



## sprocketjockey9 (Jul 18, 2006)

Ryon,
Well it really determines how your power curve lies.  That will help determine your weakness. Secondly, it depends on your goals. Are you racing xc, short track or endurance??

The numbers you have given sound like a good place to start with your FTP


----------



## butryon (Aug 12, 2005)

Jason,
I am racing mostly xc for the first half of the season and then ramping the volume up a bunch for the Trans Rockies in Aug. so the end of June and all of July are longer races. I notice that the longer 2.5 to 3.5 hr races I have my best performances. Not sure what that means but power should help me add a bit more structure to what i do.
Thanks,
Ryon


----------



## LyndaW (Jul 22, 2005)

butryon said:


> Jason,
> I am racing mostly xc for the first half of the season and then ramping the volume up a bunch for the Trans Rockies in Aug. so the end of June and all of July are longer races. I notice that the longer 2.5 to 3.5 hr races I have my best performances. Not sure what that means but power should help me add a bit more structure to what i do.
> Thanks,
> Ryon


Well cool. I'll see you at TR. I'm signed up to race open mixed again.

For TR lots of long tempo rides in power L3 is the ticket. Build up gradually to 120 mins non-stop on the gas in power L3. Do that a couple of times a week 3-5 weeks out from the start of TR.

LW


----------



## butryon (Aug 12, 2005)

Lynda,
what is L3 compareable to in terms of hr(max 186), and what wattage based on a 330w, 20 min. test? 
Also, I know some of you have had a power tap on the mtb for a while, what do I need to be careful with? What shouldn't I do and how durable are they?
Thanks,
Ryon


----------



## bbgobie (Apr 20, 2006)

Ok... I'll bite.
Why the different rotor bolt pattern?

Seems like an annoyance more than anything.


----------



## RickySilk (Jan 28, 2007)

bbgobie said:


> Ok... I'll bite.
> Why the different rotor bolt pattern?


Check out lynda's picture










The hub is much bigger. Requires a custom rotor.


----------



## jakomonster (Jun 20, 2006)

LyndaW said:


> Well cool. I'll see you at TR. I'm signed up to race open mixed again.
> 
> For TR lots of long tempo rides in power L3 is the ticket. Build up gradually to 120 mins non-stop on the gas in power L3. Do that a couple of times a week 3-5 weeks out from the start of TR.
> 
> LW


Are you and Dave taking a laptop there to download between stages? I want one too but I'd end up erasing each file without knowing my CP's and TSS.


----------



## LyndaW (Jul 22, 2005)

butryon said:


> Lynda,
> what is L3 compareable to in terms of hr(max 186), and what wattage based on a 330w, 20 min. test?
> Also, I know some of you have had a power tap on the mtb for a while, what do I need to be careful with? What shouldn't I do and how durable are they?
> Thanks,
> Ryon


Your L3 power would be 235 - 280 watts. The heart rate for this power level depends, among things on how long you have been there, how hot it is, how fresh/fatigued you are, how much coffee you have drank, how many stages into a 7 day stage race you are...

The wireless PT's - you have to be careful on keeping communication between the hub and CPU.

Cheers,

Lynda


----------



## LyndaW (Jul 22, 2005)

jakomonster said:


> Are you and Dave taking a laptop there to download between stages? I want one too but I'd end up erasing each file without knowing my CP's and TSS.


Oh I'd love to but we are coming with no support and sleeping in a tent so don't feel like putting a laptop in the gear bag thrown in a truck daily. Do you guys have a support team? If someone can take care of a laptop between stages it would be doable. We can all share and snicker over power files at dinner time...


----------



## JMK331 (Mar 9, 2008)

Those of you that have gotten a few rides on your new hubs:

Any issues? Does the signal drop out much? Would you do it again?

Thanks,
OnTheFence!


----------



## sprocketjockey9 (Jul 18, 2006)

JMK331 said:


> Those of you that have gotten a few rides on your new hubs:
> 
> Any issues? Does the signal drop out much? Would you do it again?
> 
> ...


I've put some time so far in on mine, including a nice 8 hour ride this past saturday. I've haven't had any power or data drops. If I'm off the bike for a few minutes, I might sometimes have to do a find to bring the power back, however with hr anytime I move out of range I'm forced to do a find. Kind of annoying and scary at the same time (find is really close to clear all).

After breaking in the rotor in it's worked great including on some super long forearm burning, brake fade heat inducing descents.

I ran an ergomo pro all of last season and still have it set-up, but I've yet to run the power-tap on the same bike and do a side by side comparison. So far the numbers seem pretty accurate


----------



## chainringrrl (Aug 3, 2007)

JMK331 said:


> Those of you that have gotten a few rides on your new hubs:
> 
> Any issues? Does the signal drop out much? Would you do it again?
> 
> ...


I've got a few hundred miles on mine, which I built into a heavier training rim. Honestly, I'm super tough on gear. It's been ridden through rain, mud, slop, high humidity, creeks, and most recently submerged completely into a hub deep mud pit. It's worked flawlessly. I agree that the "find" is a little too close to the "clear" function for my comfort, but otherwise it's an awesome tool.

Truthfully, I'm new to the whole "power training" phenomenon. Being a total gear junkie, I bought it mostly because it's new, cool, and shiny. However, I raced my first xc race of the season on it and got some really good info. I have no idea what most of it means, but "coach" says it was valuable. I'd totally spend the cash again.


----------



## perryr (Jul 26, 2004)

JMK331 said:


> Those of you that have gotten a few rides on your new hubs:
> 
> Any issues? Does the signal drop out much? Would you do it again?
> 
> ...


I have been using a PT wireless rim brake wheel on my MTB for about 8months. Did numerous races, mud, rain, sub freezing, about 5000 miles.

Down around 10deg the display fades, but continues to record.. just stay on top of your batteries in the cold. I rode in heavy rain, freezing rain, snow, etc.. no issues.

After a mud race I had to submerge my bike to get the mud off before 
putting it in my car. The next day it was dropping out, so I opened up the battery compartment and dumped the water out, let it dry and its been fine ever since. Definitely a solid unit!

The Disk version is basically the same with the shell modified to accomidate the disk. Killer hub!


----------



## JMK331 (Mar 9, 2008)

Thanks for all the great input. I ordered one today!


----------



## mgarrucho (May 27, 2010)

Hi, I wonder if anyone can help me. I'm trying to build a wheel on this hub (Powertap SL MTB Disc) and my rim is a mavic 717 non-disc rim (so i can use it in both types of brake system) I used an online calculator and it's giving me 259.++ at one side and 258.++ at the other side is it safe to use a 258 spoke length at with both sides then? This is at 3x lacing. Thank you.


----------



## Circlip (Mar 29, 2004)

mgarrucho said:


> Hi, I wonder if anyone can help me. I'm trying to build a wheel on this hub (Powertap SL MTB Disc) and my rim is a mavic 717 non-disc rim (so i can use it in both types of brake system) I used an online calculator and it's giving me 259.++ at one side and 258.++ at the other side is it safe to use a 258 spoke length at with both sides then? This is at 3x lacing. Thank you.


The Wheels & Tires forum is a better place for this type of question, but I'd go with 260mm for the long side. Depending on where your 259.xx is within the decimal range, you could easily come up 1.5mm short (or more) which is going to place extra stress on the nipple and threads that are in contact, if you go with the shorter 258mm. Not an issue in most cases if the spoke is a fraction too long, assuming it's not so much longer that you bottom out against the last of the threads before reaching your target tension.


----------



## WR304 (Jul 9, 2004)

Is anyone using their Powertap with the Joule 2.0 computer? The exposed USB port on the back of the computer has me a little concerned about how it's going to hold up in wet weather. 

The Joule 2.0 computer appears to be potentially quite good but definitely has some quirks - Mine doesn't always connect properly to a Windows 7 64 bit PC with it either not being detected or the CycleOps Power Agent software (7.5.1.19) crashing when you're trying to update settings on the device.

One big issue is that although the Joule 2.0 has a barometric altimeter built in there doesn't appear to be a way to manually calibrate the starting altitude. If you can't manually calibrate the altitude then it means the altitude data will always be wrong. It's currently showing -127 ft below sea level when it should be 45 ft above sea level. Hopefully a firmware update will fix that sometime.

I do like the way that you can customise the number of lines on the display. You can choose from 6, 4 or 3 lines of information where 3 lines has one really big number in the middle of the screen that should be easy to see when riding.

My Powertap SL+ hub is still off being built up so I haven't had a chance to actually try it out properly yet.


----------



## fsrftc (May 23, 2006)

WR304 said:


> Is anyone using their Powertap with the Joule 2.0 computer? The exposed USB port on the back of the computer has me a little concerned about how it's going to hold up in wet weather.
> 
> The Joule 2.0 computer appears to be potentially quite good but definitely has some quirks - Mine doesn't always connect properly to a Windows 7 64 bit PC with it either not being detected or the CycleOps Power Agent software (7.5.1.19) crashing when you're trying to update settings on the device.
> 
> ...


I'm going to pair mine with a GPS unit so I don't go off trail anymore! haha


----------



## WR304 (Jul 9, 2004)

One good thing about having an ANT+ powermeter is that you can always just change the head unit for another model easily.

A Garmin Edge 705 or Garmin Edge 500 is cheaper and has more features but articles like these ones about lost and corrupt data are a bit worrying. That was my main reason for trying a Joule 2.0 computer instead of a Garmin.

https://forums.garmin.com/showthread.php?t=10297

http://blog.kyanmedia.com/archives/2010/10/10/garmin_edge_705_data_recovery/

http://www.dcrainmaker.com/2009/11/garmin-edge-500-in-depth-review.html

Some interesting discussions of Powertap calibration and accuracy:

http://weightweenies.starbike.com/forum/viewtopic.php?f=8&t=69621

http://biketechreview.com/forum/1-general-discussion/19650-power-tap-calibration-part-two

I'm still trying to get the WKO+ 3.0 software setup as I'd like also. WKO+ 3.0 has a few good features but there are some really poor bits also. Multi File/ Range Analysis is a good example of a feature that needs sorting out so that you can actually compare rides properly. Having an X axis that can be switched between Time and Distance so the overlays line up would be a good start...


----------



## WR304 (Jul 9, 2004)

I got the built up Powertap wheel back today. I took the black plastic cover off and put some marine grease over the seals to try and help with weather proofing. There are two o-ring seals and only a small amount of visible electronics inside. You have to be careful with the plastic threads of the cover as they seem easy to cross thread. In order to remove the cover you have to take the brake rotor off first.

The Joule 2.0 computer is still playing up though. I fitted a 2gb MicroSD card but in Windows 7 64 bit it's only being detected occasionally. The picture below shows what happens when you connect the Joule 2.0 via USB to a PC running Windows 7 64 bit. Drive H: (Joule 2.0 onboard memory) and Drive I: (Joule 2.0 MicroSD card) both appear as the same size and the data on the MicroSD card isn't accessible. If you unplug and replug it a few times you can occasionally get the MicroSD card to appear but most of the time it just ends up like below.

The Joule 2.0 USB connectivity appears to work ok with Windows XP however so if there isn't a way to fix it in Windows 7 I might have to copy the .bin recorded data files onto another PC and then copy them across to WKO+ 3.0 that way..

It's not just my unit having these issues:

http://forum.slowtwitch.com/Slowtwi...n_Forum_F1/PAGING_JOULE_2.0_USERS..._P2770431

At least with a Powertap hub I should hopefully avoid the incorrect speed issues that the Joule 2.0 appears to have when used with a seperate ANT+ speed sensor: :skep:

http://forum.slowtwitch.com/Slowtwi...1/Joule_Setup_-_Include_Zeros_or_Not_P2998780

Pictured below: Powertap SL+ MTB disc hub internal pictures showing seals and batteries.

CycleOps Joule 2.0 connected via USB to a PC running Windows 7 64 bit has problems detecting the internal 2gb MicroSD card.


----------



## WR304 (Jul 9, 2004)

I've done a few rides with the Powertap and Joule 2.0 computer now. 

I took the Epic out on the road club run today and one side effect of the new Powertap was that my mates were doing some serious half wheeling whenever I was on the front - just for a laugh so they could look over at the display and see what power I was having to produce to keep up.

The power data is really interesting to look at. The difference between what the heart rate / speed readings on the display show and what the power numbers read at the same time is really striking. The main thing is that power output seems very sensitive. Even when speed and heart rate appear constant (such as when climbing a hill) the power can fluctuate a lot. I couldn't believe how much I appeared to be backing off at some points on one climb where there was clearly room for improvement as I could have changed up a gear or two. That's not something I'd noticed from just looking at heart rate / speed in the past.

Another aspect that I hadn't appreciated was just how clear the power data is for showing if you're tiring towards the end of the ride. I was starting to feel it towards the end of the ride today and even though my heart rate stayed constant the power readings dropped off a cliff for the last 40 minutes of the ride as I couldn't sustain the tempo. What you can then do is to look back through the preceding hours to see how much energy you used and how many big efforts you put in to understand why it happened.

My actual power numbers are about what I expected them to be.

*Joule 2.0 whilst riding*
On the bike I've got smoothing of 5 seconds for the power display including zeroes so that the wattage numbers are a bit more stable and don't jump around too badly. If you have 1 second data displayed the watts are all over the place. eg: the power display with one second data whilst riding at a steady constant pace would read in succession over 5 seconds - 163w, 241w, 249w, 153w, 266w. A figure that updates less frequently is much easier to gauge and use for pacing when riding.

Whilst riding the actual screen isn't too difficult to read. With the full six lines of data the top two lines are easiest to glance at quickly whilst the lower ones take a little more effort. Having the computer mounted on the stem isn't that great however because the screen is vulnerable to getting covered in sweat. Add some dirt in and it ends up smeared. The two yellow buttons (mode and interval) are usable whilst riding but the joystick and small text of the menus is quite fiddly to navigate when wearing full finger gloves.

The claimed battery life of 20 hours looks like it's exaggerated. With power and heart rate sensors connected but no backlight the battery has been down to two blobs remaining after 4 hours riding. 8-10 hours is probably a more realistic battery life.

*Joule 2.0 connected to a PC via USB*
The Joule 2.0 with firmware 14.063 really doesn't work well with Windows 7 64 bit. It's fine in Windows XP but a nightmare with Windows 7 64 bit as it can't see the MicroSD card. I've taken the MicroSD card out now and intend to use it with the 4mb of internal memory instead. This can usually be viewed in Windows 7 64 bit. A typical ride file size with power and heart rate appears to be around 100kb per hour of ride time so the 2gb MicroSD card isn't essential so long as you remember to delete the activity files occasionally.

The included CycleOps Poweragent 7.5.1.19 software is just rubbish. I've been changing settings on the Joule 2.0 through the onscreen menus instead because at least that works. You can copy the .bin activity files off the unit without needing the Poweragent software.

*Joule 2.0 with WKO+ 3.0 build 47*
WKO+ 3.0 can import the .bin recorded files from the Joule 2.0 directly which is what I've been doing. The data appears to be ok and the intervals recorded by pressing the "interval" button whilst riding appear. One quirk is that it doesn't place an interval at the start and end of the data. If you want to look at an interval from the start of the ride until the first time that you pressed the "interval" button then you need to manually add one in WKO+. The same thing occurs between the last time that you press the "interval" button and the end of the ride which also needs an interval manually adding.

It's worth spending some time going through a recorded file and annotating the intervals with enough details that you can come back to the file and work out where you were at a particular point. This makes it easier to look at an old file in the future. For example I'll always have an interval split time for the main hills, along with intervals for the major sections of a ride.

When looking at the power data in WKO+ it's worth applying some smoothing so that you can see the trends more clearly. Smoothing of 5 seconds seems to be about right so that you have a clear line for power instead of a constantly changing trace that's hard to follow. Hiding the traces that you don't use all the time helps to make the graph clearer also. I'll usually turn off cadence.

Pictured below: Sample section of recorded Powertap data in WKO+ 3.0. This interval shows a climb on the way out of town. The starting altitude is completely wrong but gradient % and meters ascended seem about right. If you look at the power trace you can see how it jumps around a lot whilst my speed and heart rate remain constant.

The big jump in power near the top is where I lifted the pace to chase down and catch a road bike who'd just turned out of a junction near the top. You can see the sharp spike of acceleration which drops off once I'm on his wheel recovering before going past shortly after the top of the climb.


----------



## redheeler (Aug 12, 2010)

Is that the same hub you asked Mike to build into my wheel? Brian says the wheels arrived in his shop on Friday and look awesome!


----------



## WR304 (Jul 9, 2004)

redheeler said:


> Is that the same hub you asked Mike to build into my wheel? Brian says the wheels arrived in his shop on Friday and look awesome!


My wheel is a Powertap SL+ MTB disc hub (manufacture date on the packaging was June 2010) with a black DT Swiss XR 4.2D rim, DT competition spokes and brass nipples. It certainly looks distinctive fitted on the bike with the massive hub and bulky brake rotor.

The hub bearings seem to spin freely, the freehub isn't too clacky and the brake rotor works fine with my Hope Tech X2 brakes. So long as the weather seals hold up it's just like any other hub in use.

Weight for my rear wheel including the 160mm custom brake rotor (weighs 160g approx) & rim tape but without a cassette or skewer came to 1250g approx. That's a weight increase of 350g or so if you're currently using a lightweight wheel and lightweight brake rotor but since I split the rim on my old wheel a while ago I've just been riding around on a generic wheel off an old bike that I had lying around (DT freehub, 32 spokes, DT Swiss 420SL rim). Compared to that wheel with a Hope 160mm floating rotor the Powertap wheel has only added 75g to the bike.:eekster: The Joule 2.0 computer is about the same weight as my Polar RS800CX with speed and cadence sensors so the change hasn't really added as much weight to the bike as I'd expected.

Even if you don't want to look at the data in depth power data can give you a useful overview of how a ride went. The graph below is for the road club ride I did yesterday but smoothed to 10 minutes in WKO+ 3.0 . This loses a lot of the detail but allows you to look at overall trends. I've highlighted the three sections of the ride in green so that you can see how the power output changes. The three dotted yellow lines are the edge of my (estimated) power zones. Anything above the lower dotted yellow line but below the middle dotted yellow line is Tempo (per Coggan zones). Anything above the middle dotted yellow line but below the upper dotted yellow line is trying hard Threshold (per Coggan zones) Anything above the upper dotted yellow line is above threshold and trying very hard VO2MAX or Anaerobic Capacity (per Coggan zones). With this level of smoothing on the graph you lose the highest peaks and troughs of the power output but what remains is an indication of overall effort that you were putting in.

(*Edit*: Corrected description of power zones)

The first section is riding to meet the club plus the first few miles of the ride where I was sitting in the group chatting. If you're not on the front then it takes a lot less effort to ride at the same pace due to slipstreaming the riders in front. You can see this in how far below the yellow dotted lines the smoothed power output falls.

The second section is riding with the club but now I'm spending some time on the front for the lead in to the climb which was flat out (the highest power output / lowest speed peak) followed by working harder afterwards for the next 18 miles or so with some long stints on the front of the group into the wind.

The third section is the interesting part. I'm now riding by myself on the way home. Although my speed still isn't too bad I'm tiring now and can't sustain the same power output anymore. This shows up very dramatically as the yellow power output trace falls away towards the end. It's really only the last 1.5 miles which is truly a descent back into town. The rest of this section superficially appears solid enough if you were just looking at the speed trace and heart rate but by looking at the power output in this way it shows that I was cracking.

At that point in the ride I was struggling. By looking at the overview of the entire ride you can see why. Throughout the club ride section I'm going into the red repeatedly and paid for it later on. You can use the smoothed view to pick out overall trends and then see if you repeat them across more rides. If you're always losing power after 2h30 for example then it's a sign that maybe you need to pace yourself more carefully early ride or possibly eat and drink more.

Pictured below: Changing power output during Sunday's club ride.


----------



## WR304 (Jul 9, 2004)

Using the Joule 2.0 computer without a MicroSD card has been working fairly successfully. I've been able to get the .bin recorded ride files off without any problems and copy them onto the Windows 7 64 bit PC.

After the first rides where the computer battery went down quickly the battery life seems to have improved now after a few charges. It was still displaying full battery after 3h30 on the bike today which seems much better also.

I've been trying to compare the Powertap recorded data to what was produced by my Polar RS800CX which recorded heart rate, speed, cadence and altitude. There are a few interesting differences that I've been trying to understand why they're happening. The main one is that the distance recorded by the Joule 2.0 (with Powertap hub) is reading higher than the Polar by about 1.4% when both were using the same tyre and identical circumference measurement. 

Another big difference is in the cadence readings. The virtual cadence of the Powertap hub is all over the place. I'm thinking about getting a VDO Z-Series ANT+ cadence sensor so that the cadence readings are more accurate than the virtual ones. I don't use cadence for much but I do like to look at the amount of time that I spent not pedalling over an entire ride. As an example over a 3hr ride with the Polar RS800CX recorded data it said that I had free wheeled for 6min39 seconds according to WKO+. When I did the same ride yesterday with the Powertap the recorded data said that I had freewheeled for 14min14 seconds over the same route.:madman: 

I've also been experimenting with some different values for power smoothing whilst riding. I ended up going back to 5 second smoothing as that seems best. If you increase smoothing to 10 seconds then the display still updates with a new figure every few seconds. Smoothing doesn't mean that the power figure displayed stays constant on the screen for 5 or 10 seconds. It just seems to mean that the power figure lags more behind your current effort.


----------



## WR304 (Jul 9, 2004)

Well the Joule 2.0 and Powertap survived their first wet ride today. It was ok for 3 hours but then the rain came in for the last hour of the ride on top of the hills. It was just drizzle but everything is still working.

There are some more odd things that I've been noticing. According to the History report viewed directly on the Joule 2.0 today's ride involved 5267 ft of elevation gain. The recorded ride file viewed in WKO+ for today's ride says that it only involved 4404 ft of elevation gain. Today's ride was all above sea level but if you do a ride where the altitude is below sea level then WKO+ interprets any altitude readings from Joule 2.0 below sea level as a fixed -3ft. Any altitude data below sea level is ignored.

Another one is the TSS and IF calculated by the Joule 2.0. I have exactly the same FTP and power zones entered into the Joule 2.0 and WKO+. According to the Joule 2.0 History report today's ride had a TSS (Training Stress Score) of 285.6 and an IF (Intensity Factor) of 0.827. The recorded ride file viewed in WKO+ for today's ride says that it had a TSS of 287.9 and an IF of 0.832. It's not a massive difference but there shouldn't be one at all. :skep: 

Normalised power, average power, KiloJoules, time, distance and average speed were the same between both the Joule 2.0 and WKO+.

In order to enter your FTP into the Joule 2.0 you have to do it through the CycleOps Poweragent software. You can set the power zones on the head unit but FTP can only be entered via a computer and the USB connection. The Poweragent software works perfectly on Windows XP (apparently it's ok with 32 bit Windows Vista and 32 bit Windows 7 also. The problem being the 64 bit operating system compatibility.) 

Being able to track TSS and IF in WKO+ is something that looks like it will be really useful as it allows you to quickly have an idea of just how hard a particular ride was. One problem I had when using a heart rate monitor for training was that my heart rate response would drop off rapidly after a few days consecutive riding to the point where the heart rate numbers didn't mean much. I'd be riding around at some ridiculously low heart rate that was way below any training zones but with good pace and no real idea of how hard a ride was in comparison to other rides.

Pictured below: Any Joule 2.0 altitude data below sea level doesn't appear in WKO+ 3.0


----------



## perryr (Jul 26, 2004)

WR304 said:


> today's ride says that it had a TSS of 287.9 and an IF of 0.832. .


BIG ride! 4h15min?


----------



## WR304 (Jul 9, 2004)

perryr said:


> BIG ride! 4h15min?


It was 4h11min. I would have done another hour or so but had to cut it short because the bite valve on my hydrabak bladder started leaking badly and I was worried about running out of drink.

The weather's been quite nice recently so I've been trying to get some miles in. 18 hours in the last 5 days.

TSS and IF are really reliant on your FTP figure being accurate. From looking at the WKO+ power distribution chart and the gaps between bars I think that I'm in the right sort of area but I haven't actually done a proper test yet. I could be underestimating my FTP which would make the current TSS and IF numbers a bit too high.


----------



## miss rides a lot (Jul 23, 2008)

WR304 said:


> Another one is the TSS and IF calculated by the Joule 2.0. I have exactly the same FTP and power zones entered into the Joule 2.0 and WKO+. According to the Joule 2.0 History report today's ride had a TSS (Training Stress Score) of 285.6 and an IF (Intensity Factor) of 0.827. The recorded ride file viewed in WKO+ for today's ride says that it had a TSS of 287.9 and an IF of 0.832. It's not a massive difference but there shouldn't be one at all. :skep:


Check the wattage forum, but I'm not sure they use the same calculation. While close, it may not be exact.


----------



## perryr (Jul 26, 2004)

WR304 said:


> It was 4h11min. I would have done another hour or so but had to cut it short because the bite valve on my hydrabak bladder started leaking badly and I was worried about running out of drink.
> 
> The weather's been quite nice recently so I've been trying to get some miles in. 18 hours in the last 5 days.
> 
> TSS and IF are really reliant on your FTP figure being accurate. From looking at the WKO+ power distribution chart and the gaps between bars I think that I'm in the right sort of area but I haven't actually done a proper test yet. I could be underestimating my FTP which would make the current TSS and IF numbers a bit too high.


For myself, 287 TSS on an MTB, off road, with 5k climbing, in 4hr 11min.. would be the kinda ride that would put me on the couch.. right after I emptied the refridgerator. The ride would have had plenty of time riding hard, and the last hour would have been somewhat brutal.

The same ride at a somewhat casual pace, still hard.. but with enough in the tank to do another hour, would be 230ish.

If your 287tss ride felt like more of an endurance pace (but still a lot of work), then you may be understating your FTP by 10-15%.

If you can't find a good spot for a 20min test, go do 4 or 5x10min repeats up a hill at a power you can hold fairly consistent from 1st to last.. that'd be quite close to FTP. Better to do them in a somewhat "un-fresh" state. For instance, do your big ride, rest a day, then the next day do the 5x10's. You'll have enough to do some 10min threshold efforts, but not that extra bit needed to repeat at levels above threshold.


----------



## WR304 (Jul 9, 2004)

perryr said:


> The same ride at a somewhat casual pace, still hard.. but with enough in the tank to do another hour, would be 230ish.
> 
> If your 287tss ride felt like more of an endurance pace (but still a lot of work), then you may be understating your FTP by 10-15%.


Yesterday's ride was on the mountain bike (as that's my only bike) but on tarmac with slicks on. It was a fairly hard ride but not ridiculous. The 4404ft of elevation gain from WKO+ is more likely to be accurate than the 5257ft of elevation gain from the Joule 2.0.

Those TSS and IF figures were really just to compare between the Joule 2.0 and WKO+ figures. It's a bit frustrating that the Joule 2.0 can't seem to get the basic calculations right. I've been trying lots of different FTP figures in WKO+ but it doesn't seem possible to make the TSS and IF between the Joule 2.0 and WKO+ match exactly. Maybe they'll fix it with a firmware update sometime.

I was feeling ok today and it wasn't too wet so I included a 30 minute interval down the A38 in the ride to try and get a feel for what my actual 1 hour time trial FTP figure might be. I was feeling quite good and it made a nice change doing a short 2 hour ride. I've attached a picture of the 30 minute interval graph below because it shows a few interesting things, especially when you compare the yellow power trace to the red heart rate trace.

If you look at the altitude trace along the bottom of the graph then you can clearly see the problem that the Joule 2.0 data in WKO+ has when altitude is below sea level. Anything below sea level just ends up as a flat line. I find altitude is a useful trace to look at as it can help you understand why there are changes in other traces. In this case having the changing altitude visible would help explain why the speed and power are going up and down so much over the course of what ought to be a flat time trial.

The A38 down to Bristol is quite flat with only some drags and small power climbs and is normally quite fast. It was blowing a gale today though. The entire 30 minutes was into a crazy headwind. I was going flat out and at one point was down to 10mph and the 33T middle ring. That's why the average speed is so low.:eekster:

When you compare the average power output to the average heart rate it shows why I've found it difficult to use recorded heart rate as a reliable measure of intensity. Heart rate relative to how hard I'm trying doesn't stay constant from ride to ride. The highest heart rate figure that I've seen this year when totally fresh was 197bpm. The average heart rate for this 30 minute time trial today where I was flat out was only 155bpm. A full 42 beats below that. If you look at those heart rates compared to the Peter Keen heart rate zones for example then 155bpm would indicate that this was a low level aerobic workout, barely above active recovery when I was actually trying to go as fast as possible.

http://www.machinehead-software.co.uk/keencalc.html

Even with the head wind you can see how the power trace falls away anytime the speed rises. It's a struggle to keep the power high at those points on the downhills making my pacing appear a bit inconsistent. This is something that a power meter shows up really well. It takes a lot of concentration to stop your work rate falling away on downhill sections. Doing a test like this on the turbo trainer or up a climb would probably give a much smoother power output overall than I managed here.

I had a look back through the other power data and there was a section of the club ride on Sunday where I managed 250 watts for 17 minutes whilst I was leading out to the bottom of the hill and then trying to stay with other riders uphill which is a substantially higher figure than the time trial today. An FTP number in that sort of range would make the TSS for yesterday's hilly ride more like what *perryr* expected to see. I'm going to do another test next week, probably uphill, and see what the power figures are like from that when I'm more rested.

Although I felt quite good today I suspect that I was actually a bit tired and could have managed a higher average power if I'd had a few days off first or chosen a different route. This is the good thing for me about having a power meter as it's a measurement that shows when I could benefit from some time off with less guess work than looking at heart rate.

Pictured below: 30 minute time trial on A38 into a head wind


----------



## perryr (Jul 26, 2004)

WR304 said:


> I had a look back through the other power data and there was a section of the club ride on Sunday where I managed 250 watts for 17 minutes


250*.95=238

That may be close?

There are all sorts of do's and don'ts when calculating FTP. Its good to have it reasonably close as the training zones are more accurate, and that is important to me.

I also track TSS with Performance manager, and use PM to help steer my training. Its also amazing for looking back on what worked, what didn't and what we might try different to find improvement. For this reason I think the testing protocal is critical to accuracy down the road when comparing seasons etc..

I use a standard 20min x.95. Its long enough to come close, but not so long and difficult that testing requires a special day, with a wekk taper and huge motivation (like a 40k).

I also use the same road.. a very mild climb that I'm very familiar with. I ride it all the time, I know how to pace it and its 10min from my house. I'll adjust FTP periodically to reset training zones and know for sure that TSS is relatively accurate. When I look back at 08', I know the FTP was set in the same way as today, and that the PMC compared with today is apples to apples.

So, my recomendation would be to seek out a test prtocal. Find the course, make sure you have a few days of recovery, do some openers the day before and then put the hammer down for an all out best avg watts. Down the road you'll be happier with the accuracy of the ride histories and the PMC.


----------



## WR304 (Jul 9, 2004)

perryr said:


> I also use the same road.. a very mild climb that I'm very familiar with. I ride it all the time, I know how to pace it and its 10min from my house. I'll adjust FTP periodically to reset training zones and know for sure that TSS is relatively accurate. When I look back at 08', I know the FTP was set in the same way as today, and that the PMC compared with today is apples to apples.


I'm glad that you mentioned those TSS figures seemed high.

Doing that 30 minute time trial yesterday showed how important it is to sort out a good route and test properly. If the FTP and TSS are incorrect then it makes it difficult to know if all the other reports derived from those figures are reliable or not.

I've got several years of historic recorded heart rate data in the Polar Protrainer 5 software. I imported October's Polar files into WKO+ but it's quite a lot of hassle because the ride details and split time text notes aren't imported with the Polar .hrm files and have to be copied in afterwards. Without power data most of the WKO+ reports don't work anyway so I'm thinking about just leaving the rest of the files in the Polar software.

The picture below shows my Powertap wheel fitted to the bike. The area around the rear axle manages to look even more cluttered than before with the bulky hub.

The Joule 2.0 headunit isn't that big. Here it's mounted on a 110mm Extralite stem. The first thing anyone who sees it asks is whether it's a GPS. It's larger than a standard computer but smaller than a Garmin Edge 705. Something interesting is that the grey and yellow colour scheme of the Joule 2.0 is exactly the same as the cover of the "Training and racing with a Power Meter" book. I think it might be deliberate.


----------



## perryr (Jul 26, 2004)

perryr said:


> 250*.95=238


I looked at my WKO+ charts and checked what the "Mean Maximal Power" curve shows for the difference between 17min and 20min. For me, the difference in the best power I can do for 17min and that of 20min is a 1-watt difference.

Therefor using 95% of 250 is reasonable. I'd bet that in future tests you will be very close (if that 17min was a max effort in a rested/recovered condition).


----------



## WR304 (Jul 9, 2004)

perryr said:


> I looked at my WKO+ charts and checked what the "Mean Maximal Power" curve shows for the difference between 17min and 20min. For me, the difference in the best power I can do for 17min and that of 20min is a 1-watt difference.
> 
> Therefor using 95% of 250 is reasonable. I'd bet that in future tests you will be very close (if that 17min was a max effort in a rested/recovered condition).


That 17 minute effort last Sunday on the club ride wasn't particularly well rested as I'd done 4 hours the day before.

It looks like I'm due some rest days now though. The aluminium bottom bracket sleeve on my 2009 Specialized Epic that the bearings press into has snapped meaning that I need a new frame.

http://forums.mtbr.com/showpost.php?p=7483777&postcount=422

I thought I'd have a go at creating a workout in CycleOps Poweragent for the Joule 2.0 to do on the turbo trainer. If you're using the Joule 2.0 computer without a power meter connected then the workout feature is useless unfortunately. The only measurement you can use to create sections within workouts is power. It's not possible to make a workout based on any other measurement such as speed, cadence or heart rate.

When you start the workout on the Joule 2.0 head unit all that is shown is the target wattage range and the watt power display. It's possible to cycle through to the normal dashboard that displays other information besides power but then you can't see countdown timer or target range.

I ended up using my Polar RS800CX for the turbo trainer session instead because with that you can use heart rate zones to set out the workout schedule properly.

Pictured below: When creating a workout schedule for the Joule 2.0 you can only use Power as a measurement and options are very limited.


----------



## WR304 (Jul 9, 2004)

One major reason for going for the Joule 2.0 computer was because I hoped that it would be more accurate and reliable when recording data than a Garmin.

Along with just looking at recorded ride data in a graph or WKO+ report it's useful to be able to export the raw data into a program such as Microsoft Excel so that you can look at a particular aspect in more depth and create your own reports. One example of that is using the 1 second recorded speed data to evaluate your braking deceleration on descents.

http://forums.mtbr.com/showpost.php?p=7104875&postcount=371

If you open Joule 2.0 ride data in WKO+ 3.0 then the "raw data" view (select 1-2-3 from the top bar) allows you to see the data in 1 second steps. The columns displayed in WKO+ include altitude and temperature. These can be manually edited one cell at a time but you can't copy to the Windows clipboard and export what you see on the screen directly to Microsoft Excel.

Instead you have to use the File - Save Copy As option and create a .csv file. This .csv file is interesting because the format must be for the older yellow Powertap headunit. When you export the data altitude and temperature are missing from the new .csv file. This happens with both Poweragent 7.5.1.19 and WKO+ 3.0 build 47. What I'd hoped to be able to do was export the data, manually correct the false altitude readings of the Joule 2.0 and then re-import the correct data.

There are some other things worth mentioning when you look at the exported files. The time field of the exported data is expressed in minutes for some reason. Each cell is one second though so you could just fill it down with a series.

At least power, heart rate, speed and cadence are the same between the software and export files which is something. Distance works out overall but distance in "raw data" view of WKO+ refuses to be anything but miles for this file. It must be a bug in WKO+ as this one doesn't change. It's somehow ended up with distance in miles but then speed in kph.

The Torque value (Hub Torque in WKO+) manages to be different depending upon whether you look at the Poweragent software, WKO+ or the .csv export from WKO+ into Excel. This is another column that appears buggy. At least one of the headings is wrong. If you do the conversion (1 pound inch = 0.11298482933 newton meter) then Hub Torque (lb-in for WKO+) equals Torque (N-m) in the WKO+ .csv file. But then WKO+'s lb-in torque figure equals the torque N-m figure in the Poweragent .csv file...

http://www.onlineconversion.com/torque.htm

What there needs to be is a way to just export the "raw data" straight from WKO+.

Pictured below: Joule 2.0 data as viewed in WKO+ 3.0 "raw data" view shows all the fields and data available in a list format.
The same Joule 2.0 data is then exported as a .csv file from both WKO+ and PowerAgent and opened alongside each other in Microsoft Excel. Note the differences in rounding between the two files, the missing fields and also how the Torque values manage to be completely different between all three sets of data.


----------



## WR304 (Jul 9, 2004)

WR304 said:


> I've been trying to compare the Powertap recorded data to what was produced by my Polar RS800CX which recorded heart rate, speed, cadence and altitude. There are a few interesting differences that I've been trying to understand why they're happening. The main one is that the distance recorded by the Joule 2.0 (with Powertap hub) is reading higher than the Polar by about 1.4% when both were using the same tyre and identical circumference measurement.


It took me a while but I've finally worked out why the distance recorded by the Joule 2.0 (with Powertap hub) and Polar RS800CX is different when using the same tyre and the same circumference measurement.

The reason is that the Polar RS800CX speed sensor was mounted on the front wheel. It measures rotation of the front wheel/ tyre whilst the Joule 2.0 measures rotation of the rear wheel/ tyre via the Powertap.

My tyre circumference was reached by rolling the bike alongside a tape measure for one wheel rotation. Although the front and rear tyres may have the same circumference in a static rollout measurement their circumference whilst riding will be smaller than this measurement. When you sit on the bike and ride your weight compresses the tyres slightly making the riding tyre circumference smaller than the static tyre circumference measured on a tape measure. There's always going to be a difference between the static and riding circumference of the wheels.

The two tyres don't compress equally. When riding significantly more rider weight is on the rear tyre than the front tyre which compresses it slightly more than the front tyre. This means that the rear tyre will have a smaller circumference than the front tyre. Over the course of a ride the front and rear wheels don't rotate exactly the same number of times. This is what causes the difference in distance between the two computers where one is counting front wheel rotations and one is counting rotations from the slightly smaller rear wheel.

If the tyre circumference entered in the computer is larger than the actual wheel circumference then it means your distance travelled and average speed will be artificially inflated. This matters more when distance/ speed is calculated from the rear wheel than from the front wheel because of the increased difference between the static circumference of the rear tyre compared to the smaller compressed riding circumference of the rear tyre. There's less of a difference between the front tyre's static and riding circumference so it doesn't create quite as large an error.

This is actually quite an important point because it means that when using a Powertap hub to measure speed/ distance you can't safely use the static tyre circumference. If you do then all your speed/ distance data will be inflated when compared to the distance that you actually travelled, and by a greater amount than if you were using a front wheel speed sensor.

The solution is to measure the actual riding circumference of the rear tyre. In order to do this you put a single spot of something that will leave a clear mark on the ground onto the tyre with each tyre rotation (eg: a blob of white grease), ride along seated in a straight line for a few metres and then measure the distance between blobs left on the ground. The distance between two blobs is the riding circumference of the tyre which you can then use as the wheel circumference figure in your computer for a more accurate speed/ distance reading.


----------



## WR304 (Jul 9, 2004)

I ran into an issue with the Joule 2.0 head unit that I haven't read about anywhere. Managing to corrupt the ride data was a bit of a surprise.









Data recording on the Joule 2.0 head unit can't be stopped or started manually. It automatically begins and pauses recording when either speed or heart rate is registered. I have it set to auto start/ pause on speed. The last time I used the unit was a few weeks ago. At the end of that ride I stopped at the top of the drive and pressed "Stop and save ride" which creates a new data file and resets all the onscreen totals so that the display reads zero for elapsed time and distance. After resetting the head unit I then pushed the bike from the top of the drive to the house.

During this time the wheel obviously span fast enough to register and add 2 seconds to the timer. The bike then sat unused for several weeks due to the frame breaking and then the snowy weather. After those weeks I finally got to ride outdoors and didn't think to reset the timer first. 2 seconds doesn't make much difference to the average speed. When I finished the 3 hour ride I saved the file and connected the head unit to the PC to import the file.

The file had the date from several weeks ago and a ride time of 4 seconds. What had happened was that the file had begun weeks ago, but the overall time kept increasing whilst the head unit sat in a drawer paused. The unit keeps track of both moving time (2 seconds) but also stationary time. That stationary time had become so large (hundreds of hours) that it couldn't deal with it anymore. So long as you remember to reset the recording before every ride then this problem won't happen. Forgetting to reset the recording is an easy mistake to make as there's no indication on the display that it's doing this

Exporting the data to a .csv file showed the first few seconds were ok but then every other time entry had become 4 seconds. The distance and speed data was still intact so it was possible to repair the file. This meant it was possible to recover the data. In order to do this you need to overwrite the corrupt time data with the correct time data. With a Powertap the head unit records at one second intervals so each cell in the .csv file represents one second. The .csv file expresses the elapsed time in minutes so each second is 1/60 = 0.01666 recurring.

Step 1 - Make sure that cell A2 is 0.01666 recurring. 
Step 2 - In Microsoft Excel next highlight only the cells of the time column of the .csv file which have data in and select Fill- Series. 
Step 3 - In the step dialog box enter 0.01666 recurring (copy and paste from a cell for more decimal places) and press ok. This will make each data cell increase by 0.01666 (one second). 
Step 4 - Save the file as a .csv with a new name. 
Step 5 - Re-import the file into WKO+ or Poweragent by selecting File- Open Workout within WKO+ and browsing to the new .csv file. If it looks ok select your user from the Workout settings list, select the correct date, enter the ride details and press save to update your new file.

I've tried to go into some detail about fixing the file because this is a really easy mistake to make if you forget to reset the head unit. 

Pictured below: Using Fill - Series in Microsoft Excel to repair corrupt Joule 2.0 data in a .csv file


----------



## WR304 (Jul 9, 2004)

This Youtube video is where *DC Rainmaker* tests the weatherproofing of several power meter head units: The Garmin Edge 800, Garmin Edge 500, Garmin Edge 705 and Cycleops Joule 2.0. They seem to fare quite well.

http://www.dcrainmaker.com/2010/12/feeling-lucky-water-immersion-tests.html






My Powertap has mostly been working ok. I've been concentrating on short 2 - 2.5hr rides at the moment with some intervals built in whilst trying to keep the intensity factor high. What I'm liking about the power meter is that it lets you compare rides on an "apples to apples" basis. A good example is being able to look at current rides when the bike has offroad tyres fitted and still directly compare the power output to the rides on slick tyres that I did in November 2010.

For doing intervals the power meter shows just how inconsistent my pacing during intervals can be. The power outputs below being a set of 6 x 4 minute intervals outdoors from the other day. They all felt hard when I was doing them but looking at the recorded data the power output was erratic. It's something to work on improving.

Interval 1: 226 watts
Interval 2: 205 watts
Interval 3: 217 watts
Interval 4: 199 watts
Interval 5: 205 watts
Interval 6: 224 watts

The Powertap hub hasn't done many miles but I've been having a few data drop outs like the one pictured below. I'm wondering if maybe it had been sat on a shelf for a long time and could do with some fresh batteries already?

Pictured below: Powertap Data Drop Out


----------



## Litemike (Sep 13, 2007)

I'm a training with power newbie (I do not have a power meter) but I have a question - does the power tap give you an upsift or down shift based on your altitude / hr / current power output?


----------



## WR304 (Jul 9, 2004)

Litemike said:


> I'm a training with power newbie (I do not have a power meter) but I have a question - does the power tap give you an upshift or down shift based on your altitude / hr / current power output?


I'm not sure what you mean by upshift or down shift in terms of a power meter? 

No current power meter head units are linked into the bicycle's gears. It's not like the Shimano Flightdeck computer which displays what gear you're in on the screen of the bike computer whilst riding.

You can estimate where you changed gear from changes in cadence and power output when looking at the graph post ride. It's actually easier from the cadence trace than power though. Spikes in cadence often signify a downshift whilst a drop in cadence followed by an increase in power can mean an upshift. The Powertap virtual cadence isn't that accurate however. It's much easier to look at with a proper cadence sensor that actually counts crank rotations.


----------



## PissedOffCil (Oct 18, 2007)

One solution to getting upshifts and downshift is to use the Gears plugin for SportTracks. After configuring your wheelsize and gear ratios, it does a very good job of reproducing your gearing for a ride! Of course you need a cadence sensor and it'S only available post ride.

I use it somewhat often with my Filtered Stats plugin to find where I used certain gears (ie little ring)


----------



## WR304 (Jul 9, 2004)

I thought you might be interested in some power output comparisons between October 2010 and mid January 2011.

With a power meter it's possible to evaluate what sort of performance decrease 6 weeks of limited cycling can have on power output, and also how long it may take for power output to return to the same levels again when training is resumed. October 2010 wasn't my best month of last year, but I was quite fit and is the earliest that I have any power data for. Weight stayed stable at 154lbs.

Mid November 2010 and all of December 2010 were a complete disaster in terms of cycling. My bike broke, then it snowed and I also managed to catch flu over the Christmas period. That meant I did hardly any cycling during that period - some turbo training intervals and a bit of weight training but not much (8 hours total in December). There must have been some detraining during that time.

The table below shows the best 1 minute, 5 minute, 20 minute and 60 minute power output numbers for October 2010 and then the best power output numbers for each week of 2011. The red numbers are the shortfall in power output for 2011 compared to October 2010. It shows that I lost a significant amount of power from the 6 weeks of limited riding. A few weeks of solid riding has seen the power numbers begin to improve rapidly again though. Whether that will keep going or begin to plateau still has to be seen.

Calculating a reasonable FTP figure (best 1 hour time trial pace) is still proving difficult. I've been using 220 watts for now as I suspect that I could possibly do that for an hour if I was pushed hard enough in a race situation. As you can see from the table I'm getting nowhere near that hourly power output in normal riding, even doing short hard rides, so possibly I should be using a lower FTP? The problem is identifying the gap between what I'm doing currently and what I can _actually_ manage.

This thread on the subject is worth looking at:

http://www.cyclingforums.com/forum/thread/482524/discrepancy-between-cp-and-1-hour-power

Pictured below: My best Power output numbers for October 2010 compared to the first weeks of January 2011.* Edited * to add the TSS figures for January 2011. I didn't have a powermeter for all October 2010. The one week I did with the Power meter in 2010 had a TSS of 1,234 but that was spread over 18 hours of riding.


----------



## WR304 (Jul 9, 2004)

WR304 said:


> The Powertap hub hasn't done many miles but I've been having a few data drop outs like the one pictured below. I'm wondering if maybe it had been sat on a shelf for a long time and could do with some fresh batteries already?


The drop outs have been getting increasingly frequent so it looks like the hub batteries are going. There were several in today's ride so I'm going to try replacing the batteries with new ones. The batteries needed for the Powertap hub are:

2 x 357 batteries for the hub

Something that's good with the Powertap is that when riding you can clearly tell when you're tired because it's so difficult to sustain the required power output. Today was a good example:

It was a nice day so I thought I'd do a longer ride but with a few intervals and hills thrown in to make it more challenging. I manage the first few intervals ok but after just 50 minutes into the ride I'm cooked. This was very obvious from how the power output was falling away. Not great when there was still another 2h40 of riding and all the major climbs still to come.:nono:

Looking at the downloaded data post ride the first 50 minutes of the ride was at an average of 187 watts but then the rest of the ride was a much lower average of 155 watts. Time for a day off.


----------



## WR304 (Jul 9, 2004)

WR304 said:


> The drop outs have been getting increasingly frequent so it looks like the hub batteries are going. There were several in today's ride so I'm going to try replacing the batteries with new ones. The batteries needed for the Powertap hub are:
> 
> 2 x 357 batteries for the hub


I replaced the batteries in the Powertap hub and it looks like that was the problem. There were no data drop outs at all in today's ride.

The original batteries only lasted for approximately 60 hours of riding. I'm hoping that starting with fresh batteries means the hub will last a bit longer before they need replacing again.

One thing that's really annoying me is the barometric altimeter on the Cycleops Joule 2.0 head unit. There was about a week where the outdoors temperature increased and the altimeter recorded positive altitude values. The outdoors temperature has dropped back down towards 0c and the altimeter is at -572 feet again. As it can't be calibrated to the correct starting point that means no altitude data is viewable in WKO+, even for the hilly rides.:madman:

I've been seriously thinking about getting a Garmin Edge 800 as a replacement but all the threads about corrupt Garmin Edge 800 .fit data files which can't be uploaded, loss of connection to Powertap hubs, cracked touch screens etc have me wondering whether it would actually be any better than the Joule 2.0. :skep:

Garmin Edge 800 corrupt data
https://forums.garmin.com//showthread.php?t=15674

Garmin Edge 800 loss of connection to Powertap hub
https://forums.garmin.com//showthread.php?t=15826

Garmin Edge 800 cracked touch screen
https://forums.garmin.com//showthread.php?t=14493


----------



## PissedOffCil (Oct 18, 2007)

I love my Edge 705, couldn't it be a good alternative? The 800 doesn't have that many interesting new features honestly.



WR304 said:


> I replaced the batteries in the Powertap hub and it looks like that was the problem. There were no data drop outs at all in today's ride.
> 
> The original batteries only lasted for approximately 60 hours of riding. I'm hoping that starting with fresh batteries means the hub will last a bit longer before they need replacing again.
> 
> ...


----------



## LMN (Sep 8, 2007)

WR304 said:


> The drop outs have been getting increasingly frequent so it looks like the hub batteries are going. There were several in today's ride so I'm going to try replacing the batteries with new ones. The batteries needed for the Powertap hub are:
> 
> 2 x 357 batteries for the hub


The ability to replace the batteries in a Powertap is the reason they are superior to SRMs. You have to send SRMs away to get the batteries replaced, which
a) Takes a fair bit of time
b) Is stupidly expensive ($200+)
c) The north american company that does it, isn't very good at calibrating them.


----------



## bholwell (Oct 17, 2007)

LMN said:


> The ability to replace the batteries in a Powertap is the reason they are superior to SRMs.


Doesn't Alison's husband work for SRM now? Maybe you could get him to work on that...?


----------



## MisterC (May 17, 2007)

When quarq comes out with a mountain option, I will probably go that route. My road version is about 3 weeks out. very excited.


----------



## MisterC (May 17, 2007)

And I know this is petty but, the edge 500 and 800 win me over due to the mount almost all by itself.

I just could not stand that sliding clasp thingy on my 705. I broke two of em in frustration trying to get the damn thing off of there.

The twist mount is infinitely better IMO.


----------



## PissedOffCil (Oct 18, 2007)

MisterC said:


> And I know this is petty but, the edge 500 and 800 win me over due to the mount almost all by itself.
> 
> I just could not stand that sliding clasp thingy on my 705. I broke two of em in frustration trying to get the damn thing off of there.
> 
> The twist mount is infinitely better IMO.


I've been abusing mine (3 on 3 bikes) without a problem for as long as the 705 came out. Some folks are rough with their mounts, I've read numerous stories of them breaking but never understood how they did it.


----------



## WR304 (Jul 9, 2004)

PissedOffCil said:


> I love my Edge 705, couldn't it be a good alternative? The 800 doesn't have that many interesting new features honestly.


I'm dithering badly about what a good power meter head unit option would be. They all seem to have some disadvantages. You don't really know how easy they are to live with until you actually get to try them out.

The thing I like in theory about the Garmin Edge 800 over the Edge 705 is that it has a touch screen instead of a joystick. The joystick for navigating menus and displays on the Cycleops Joule 2.0 is fiddly and a nightmare to use when wearing winter gloves.

With devices like these Garmins you're very reliant on firmware updates. When a newer model comes out the older ones often become a lower priority for updates. A newer model seems like it would be more likely to have ongoing support. The argument with the Garmins seems to be that it takes a few years before their products actually work properly.



LMN said:


> The ability to replace the batteries in a Powertap is the reason they are superior to SRMs


Changing the Powertap hub batteries would be a lot easier if they'd designed the hub so the plastic tool can unscrew the cover without needing to remove the brake rotor first.

I was a bit hasty thinking the new batteries had solved the issue. There were two dropouts in yesterday's 2h30 ride and three dropouts in today's 2h45 ride so it's still happening. The dropouts appear to be totally random whilst out in the middle of the countryside. I don't know if it's the head unit or the hub? On the plus side the dropouts are all short like the one pictured in post #75 so they're only losing a few seconds of data each time. When riding I'm not noticing the dropouts as they're short gaps. They only show up when reviewing the data post ride.

One thing I'm trying to understand is why there's a clear gap between my climbing power output and flat power output. It's not the same as *Battle Duck*'s thread because all of my data is whilst riding seated.

http://forums.mtbr.com/showthread.php?t=676171

The two graphs below are extracts from today's ride (The altimeter had gone wrong so there's no altitude data). The seated climb is up a 6.6% average gradient hill. I was using the 23T rotor granny ring. The flat ride section is the final 10 minutes of the same ride home on the 44T round big ring where I was flat out and going as hard as I could. For a similar average heart rate and average cadence I managed 240 watts average climbing but only a poor 215 watts on the flat.

There's got to be an obvious explanation.

Pictured below: Differences in seated climbing power output up a 6.6% gradient hill and flat power output from today's ride.


----------



## whybotherme (Sep 12, 2008)

bholwell said:


> Doesn't Alison's husband work for SRM now? Maybe you could get him to work on that...?


Ha! No. I don't work for SRM, or any other cycling related company. Wish I could help. I could recommend some good angioplasty catheters though.


----------



## bholwell (Oct 17, 2007)

whybotherme said:


> Ha! No. I don't work for SRM, or any other cycling related company. Wish I could help. I could recommend some good angioplasty catheters though.


No, sorry, not you- Alison Dunlap's husband.


----------



## whybotherme (Sep 12, 2008)

bholwell said:


> No, sorry, not you- Alison Dunlap's husband.


cool. sorry for the confusion.


----------



## WR304 (Jul 9, 2004)

One of my big reasons for getting a power meter was for comparing ride intensity and trying to evaluate whether I was tired or not.

The problem being that after a few weeks of solid riding my exercise heart rate response would be very low, even though I felt good. I'd end up ignoring the heart rate monitor most of the time as I simply didn't believe what it was telling me.

http://forums.mtbr.com/showthread.php?t=673646

My hope was that the power meter would give a more objective measure that I could rely on. So far this has been working quite well. When riding the drop in performance when you're tired, both in terms of Intensity Factor and average power is very noticeable. A quick glance at the report is all it takes to show which rides were good and which weren't so far this year.

The WKO+ report below shows the rides that I've done so far in January 2011. The red line is average heart rate whilst the yellow line is average power for the same ride. You can see immediately that most of the rides have been fairly solid, apart from three which have much lower average power. The two days marked with a 1. are active recovery rides, whilst the ride marked with a 2. is the one mentioned in post #80 where I blew up badly. When you view the data in a report these stand out clearly as being different from the others. If you blow up it's reflected in the data.

I mentioned that I found heart rate an unreliable tracking measure and you can see that pattern emerging here also. For the first week or so the red heart rate line is higher than the average power line, but then the trend reverses mid month and the red heart rate line falls below the average power line. It's most marked at the point marked 3. on the report where I was doing 2h30 each day. My average heart rate per ride drops badly to as low as 148 bpm, even though I'm still feeling ok and able to maintain the average power output of previous rides.

The Intensity Factor for most rides was in the .85 to .93 range (assuming my FTP is right...) I've left IF off the report below because you can't adjust the axis scales in WKO+ reports. All the different lines and bars end up in a difficult to view mass. It's quite a serious omission from the WKO+ software.

The power meter is useful for ensuring active recovery rides are in the right zone too. It's all too easy to end up going harder than you'd think. Keeping the power output low enough on an active recovery ride seems to involve bottom gear whenever there's any sort of slope at the moment.

Pictured below: My Average Power and Average Heart Rate trends for January 2011 so far. It shows that my heart rate and power output aren't always closely related.


----------



## WR304 (Jul 9, 2004)

It's possible to use recorded power data as a way of deciding the best pacing strategy for a ride or climb. Going as hard as possible isn't always the best option.

*Burning "Matches"*
_A "match" is an elusive term used by riders, and coaches within the bike racing world. When you burn a match, you have done a hard effort. It's an effort that in which you had to dig deep, or you had to really push yourself. 
...
Why do you need to know what a match is? Well, you as a rider, start out the day with a full set of matches in your matchbook, but every time you go hard, do an attack, have to hammer over a hill, you burn one of your matches. All of us have different size matchbooks, but nobody has an infinite number, so it's important to burn your -matches- at the right time during a race or in training. Otherwise you are left with an empty matchbook and then your chances of performing well have been drastically reduced." _*Hunter Allen*

http://www.peaksware.com/articles/cycling/what-is-a-match,-by-hunter-allen.aspx

When reviewing power meter data you can look through and note where the hardest efforts were. A theme in many of my rides was the observation that hard efforts were often followed by a sag in power output as I struggled to recover, losing more time than the hard effort had gained.

One of the worst of these was part of a short ride that I had done on 13 Jan 2011. I got to the second hill of the day and went hard up the first gentle 5.7% gradient section at 230 watts. The climb then ramps up steeply mid way to 10% gradient. I went up the steep section as hard as I could, peaking at 291 watts for 42 seconds, putting me deeply into the red "anaerobic zone" according to the Coggan power zones. As a result I had to slow down to try and recover. I could only manage 195 watts average power output for the remainder of the climb, which is a 4.5% gradient. It took a long time to recover after the climb also.

I did the same ride today. Remembering what had happened last time I decided to try a different strategy for the climb. I could see from the power data that the steep section looked like I'd burned a "match" as the 291 watts power output was 132% of my (estimated) 220 watts FTP. This time I decided to try and pace myself up the steepest section using the power meter instead of going flat out. I knew I'd lose some time on the steep section but hopefully make it back later.

*Comparing Climbing Pacing Strategies*
The graph below shows the climbing power output from 13 Jan 2011 (magenta) overlaid with the climbing power output from 25 Jan 2011 (yellow). It's easier to see if you zoom the picture in your browser.

The four dotted lines are the edges of the different power zones. Anything above the upper dotted line is "anaerobic zone". The first section of the climb is highlighted in green. I rode the lower section of the climb at a similar average power output on both days. 13 Jan 2011 was slightly quicker here because I carried more speed through the bend that leads onto the climb.

The steepest section of the climb is very different however. Instead of going competely flat out I used a lower gear. I was still trying hard but only in the "anaerobic zone" for 19 seconds at 272 watts. Half the time when compared to 13 Jan 2011. I was only 4 seconds slower too despite riding at a lower intensity!

The benefits of this approach are apparent in the time and power output for the top section of the climb where I was able to maintain the power output at 232 watts on 25 Jan 2011 as opposed to 195 watts (and struggling) for the same section on 13 Jan 2011.

I was also able to recover quicker after the climb and keep the pace high for the rest of the ride. The final totals for the entire ride being 1h 36 min at an average of 188 watts for 13 Jan 2011. 25 Jan 2011 was 1h 34 min and 36 sec at an average of 200 watts. All that time difference was gained in the section of ride after the climb pictured below as I felt able to keep pushing. The two rides had been very even until then.

Pictured below: Variations in pacing when climbing on two different days. Yellow is 25 Jan 2011, Magenta is 13 Jan 2011. Zooming the picture in your browser makes it easier to see both traces.


----------



## WR304 (Jul 9, 2004)

I've been trying to compare the energy expenditure (kilojoules) as calculated by my Powertap with the energy expenditure (kilo calories) that was calculated by my Polar RS800CX heart rate monitor. I wanted to see how comparable the energy expenditure calculation was between the two devices. In theory you can simply say that 1 kilojoule measured by the power meter is equal to 1 kilo calorie because of efficiency losses (instead of converting the kilojoules into calories).

The kilo calories burnt calculation of a heart rate monitor is highly reliant on the initial user values that you enter into the heart rate monitor (age, weight, exercise level, Max HR, VO2 Max etc.) The energy expenditure is then estimated using a formula based on these values. As a result the kilo calories burnt figure calculated using a heart rate monitor can be wildly inaccurate - often over estimating the numbers of calories burnt.

Have a read of this web page and try out the calculator to see how the estimated kilo calorie usage numbers change when you use different VO2 Max and age values (age in this formula adjusts your maximum heart rate). If you use an estimated maximum heart rate and estimated VO2 Max for the settings (as opposed to knowing your actual maximum heart rate and having a lab tested VO2 Max) then it introduces errors into how the heart rate monitor calculates energy expenditure.

Calorie Expenditure Calculator:
http://www.braydenwm.com/calburn.htm

Whilst I was looking at various articles the interview discussing energy expenditure below was linked. I've posted it here because it seems relevant when considering what a Powertap can be useful for.

Full Discussion:
http://www.bikeforums.net/showthread.php/179758-calories-burned-seem-low

**************************************************************************************************
*Energy In, Energy Out: What's the Magic Equation? (Part I)*

A few weeks ago I was going through a thread on slowtwitch.com discussing caloric expenditure on the bike and the accuracy of the kcal numbers on our HRM's. I always assumed that the variables in caloric expenditure could never be accurately determined by heart rate alone; temperature, hydration, force, etc all have a direct effect on energy needs, right? In order to get a better understanding on our energy needs I contacted Richard Stern*, cycling and multisport coach of cyclecoach.com, Gordo Byrn of coachgordo.com, and my coach, Lauren Maule.

I'll begin this series with Richard. Reading his in depth explanations on the slowtwitch thread - "Fat loss question" are what set me on this quest. I began my inquiry by asking Ric simply, why is the Polar computer inaccurate and by how much?

Stern: Energy Expenditure (EE) is related to power output, as EE = power x time. This is actually the mechanical energy used to drive the bike but is actually close enough to actual EE. The mechanical energy is actually in kj (kilojules), but can be converted to kcal (kilo calories) -- the more usual metric for nutrition.

Supposing, that a cyclist averaged 200 watts (W) for 3-hours, the mechanical energy (ME) would be: ME = power (/1000) x time (secs) = (200/1000) x (3 x 3600) = 0.2 x 10800 = 2160 kj

However, 1 kcal is equal to 4.18 kj, thus, 2160 kj is equal to 517 kcal. Obviously, this would be a very low EE for a 3-hr ride. Interestingly, efficiency during cycling is ~ 20 - 25% in trained riders, so these two figures approximately cancel, and we can then say that 2160 kj ride is approximately a 2160 kcal ride.

Efficiency (thermodynamic efficiency), is a measure of the actual mechanical work accomplished divided by the input of energy. This is mainly affected by cadence in cycling. Paradoxically, efficiency is *highest* at lower cadences, and lower at higher cadences. This is because energy is required to just move the legs (with example, no chain on the bike) and higher cadences require more energy. However, as power output increases, efficiency also increases. Therefore, topographical conditions have an effect on efficiency as you tend to pedal slower uphill and faster on the flat.

The biggest retarding force in cycling is air drag (hence the reason why we all try to get as aero as possible). If for example, you have two bikes a TT aero one, and a standard road bike, at the same speed under the same environmental and topographical conditions you'll need to produce less power on the TT bike than the road bike.

Heart rate can vary for a multitude of reasons, e.g., temperature, topographical conditions, humidity, fatigue, stress, caffeine, etc. Heart rate can vary quite dramatically even at a constant power output. As an example, when I complete 20-min TT intervals at the same power (ridden indoors on a trainer) my HR can vary by ~ 15 to 20 b/min depending on the session the day before, what I've done just before, fatigue, etc. Heart rate therefore becomes 'unreliable'.

Therefore, knowing power is the only realistic way of calculating energy expenditure, as trying to estimate it EE from e.g., HR is just too variable. Thus a HR monitor won't give an accurate or useable EE for cycling as there are too many variables not accounted for.

KP: Without the benefit of having a power meter, how can one assess their caloric expenditure while cycling (assuming they use an HRM)?

Stern: Basically, unless you want to do a reasonable amount of analysis it's pretty much impossible to estimate EE without a power meter, and get a meaningful answer.

KP: I read on Gordo's site that Molina is of the opinion that the average well trained athlete burns 100 kcal per mile and an elite runner could burn as little as 50 per mile. Do you agree? Can you speculate on how this translates with swimming?
Stern: It's generally easier to calculate EE in running because speed varies less than in cycling and position isn't as important. However, running economy does vary between individuals.

KP: What do you suggest for your cycling and multisport athletes that you coach who lack power meters?
Stern: I don't suggest that they attempt to track EE. It would be very unreliable data.

KP: Do the foods consumed and their micronutrient content affect the balance of fat used to other fuel sources? How can one maximize fat usage as opposed to glycogen and protein?

Stern: Other than by training and getting fitter (i.e., increased VO2 max, increased LT) there is little or nothing that can be done to affect substrate usage. As we get fitter, we use more fat at a given intensity compared to glycogen. As the duration increases there can be a shift to greater fat usage. As relative intensity increases there's a greater use of muscle and liver glycogen (i.e., for an Olympic/sprint you'll be exercising at a higher intensity than an Ironman distance event, and using more carbohydrates).

During exercise, it's important to keep taking in carbohydrates and fluids. There's unequivocal evidence to support the use of carbohydrate during events longer than one hour (and some evidence for less than one hour). Taking in 0.7 g carbohydrate / kg body mass has been shown to unequivocally extend performance (e.g., 30 to 60 g / hr).

During exercise fluid intake is crucial to prevent dehydration: this can be achieved with 150 - 350 mL (milliliters) of a carbohydrate-electrolyte solution every 15 - 20-mins, starting at the beginning of exercise. The carbohydrate-electrolyte solution should be 4 to 8% and contain sodium. The electrolytes stimulate the thirst mechanism and can help prevent hyponatraemia in susceptible people.

KP: Can one determine optimal power to weight ratio without a power meter? Some try so vehemently to lose weight they end up costing themselves power in the process. Can one determine their optimal power to weight ratio by doing say, a specified hill or TT course over a period of weeks and comparing weight, time's, effort level, and HR?

Stern: Within the confines of losing typically small amounts of mass (e.g., ~1 or 2 kg) it will make little or no difference to performance. Unless you have a large amount of fat to loose, then it's virtually always better and easier to gain power compared to losing weight (as a primary goal). In fact, with a lot of the riders that I coach, whilst training intensely for increases in e.g., LT power output or power at VO2 max, they end up losing some fat due to the increased training energy expenditure. During flat ground cycling there's little to be gained by loosing small amounts of weight and even on hills it will only add a very small amount of time. Power to mass ratio is of more importance when e.g., cycling uphill.

More to follow in the next installment.

**Richard Stern *is a cycling/multisport coach in UK and retains the copyright on the material used in this interview. For more information, visit www.cyclecoach.com or click on the banner below.

***************************************************************************************************

.


----------



## WR304 (Jul 9, 2004)

There was a short article about the Fisica ANT+ sensor key on the *DC Rainmaker *blog.

It lets you use ANT+ to connect sensors such as the Powertap hub to your iphone or ipad and use it as a head unit.

http://www.dcrainmaker.com/2011/01/weekend-and-wedding-update.html

http://www.dcrainmaker.com/2010/05/first-look-at-wahoo-fitness-ant-iphone.html

http://www.wahoofitness.com/Fisica/Wahoo-Fitness-Fisica-Fitness-Sensor-Key.asp

The example was of overlaying your live power data on the screen with a video. It might be interesting if you do a lot of indoor training and want some extra motivation.

Pictured below: *DC Rainmaker* live power data overlaid on a ipad.


----------



## WR304 (Jul 9, 2004)

WR304 said:


> One of my big reasons for getting a power meter was for comparing ride intensity and trying to evaluate whether I was tired or not.
> 
> The problem being that after a few weeks of solid riding my exercise heart rate response would be very low, even though I felt good. I'd end up ignoring the heart rate monitor most of the time as I simply didn't believe what it was telling me.


A lot of the things which I'm finding when riding with a power meter appear fairly obvious. What it does is provide the supporting information to actually prove it either way - whether I really was being lazy and riding around at a low intensity as the heart rate monitor was saying, or whether I was trying hard like my perceived exertion indicated.

The graph below is an updated version of the chart from my earlier post. This one has the rides grouped into weekly blocks and is up to 30 January 2011 for five full weeks. This style of report hides the detail of individual days but it does give an overview of how my heart rate and power output has changed over the month. It appears to largely confirm what I'd suspected - that even when my heart rate response is low I can still have good pace, be trying hard and improving.

In the final week of January 2011 I set my best peak power records (for January) at 5 seconds, 1 minute, 20 minutes and 60 minutes which was encouraging. Without Monday's active recovery ride included the final week to 30 January 2011 was also the best overall (178 watts average, 146 bpm heart rate and an IF of 0.87 for 11h 45 min!). It's still a way off October 2010 but shows progress.

At the same time however my average heart rate has fallen significantly over the same period - from an average of 166 bpm in the first full week of January 2011 to an average of 144 bpm in the final week of January 2011. If you were looking purely at the WKO+ heart rate zone summaries for the last few weeks then you'd conclude that I'd just been doing lots of long steady distance riding without any intensity, which is a misleading picture.

I need to sort out what my real FTP is though. I'm still using 220 watts for the FTP figure used to calculate these IF and TSS figures. I think it may need revising upwards for February. I'm nowhere near being able to manage even 220 watts for a full hour in actual riding though. The best I've managed so far this year was an average of 202 watts for an hour.

Pictured below: My weekly totals for average power and average heart rate to 30 January 2011. The power output stays constant but heart rate falls steeply.


----------



## fux (Oct 21, 2006)

I am in the prosess of buying a powertap for my road bike.

Am I wrong in thinking the functions on the SL+ and Pro+ are the same but the SL+ is carbon/lighter? I already have a garmin 500, so i`m just looking at hubs.

I have both 26 and 29 inch wheels on my MTB`s and most of my intervals are done on the road so I think that is the best option for me.

I train watt on my fortius in the winter and would like to do it outdoors during the season too.

There is a lot of cool info been posted up in this thread and i`m looking for a nice gift from my wife for my 40th birthday this year.


----------



## PissedOffCil (Oct 18, 2007)

fux said:


> I am in the prosess of buying a powertap for my road bike.
> 
> Am I wrong in thinking the functions on the SL+ and Pro+ are the same but the SL+ is carbon/lighter?


Marginally lighter, that's the difference. I got the Pro+ because it's a training wheel after all.


----------



## fux (Oct 21, 2006)

Thanx, Pro+ it is then.


----------



## WR304 (Jul 9, 2004)

fux said:


> I am in the prosess of buying a powertap for my road bike.
> 
> Am I wrong in thinking the functions on the SL+ and Pro+ are the same but the SL+ is carbon/lighter? I already have a garmin 500, so i`m just looking at hubs.


You currently don't get a choice of models for the MTB Powertap. The only option is the most expensive SL+ if you use disc brakes.

The difference in price between the new Powertap road models appears to be purely down to differing construction and materials used. You're paying for a part carbon hub body and alloy axle / freehub, rather than different internal electronics.

http://www.cycleops.com/products/power-meters.html

*Road Powertap SL+*
•15mm Alloy axle and free hub body
•Carbon/alloy hubshell
•Hub weighs 412 grams

*Road Powertap Pro+*
•15mm Alloy axle and free hub body
•Alloy hubshell
•Hub weighs 466 grams

*Road Powertap Elite+*
•15mm Steel axle and free hub body.
•Alloy hubshell.
•Hub weighs 583 grams

If you're looking at road Powertaps for a training wheel then I think I'd choose the Powertap Elite+. The reason being that it has a steel freehub body which will be more reliable as it won't be damaged by Shimano cassette splines. Weight doesn't really matter for a training wheel.

The MTB disc version of the Powertap SL+ hub has a steel freehub body according to the product page:

*MTB Powertap Disc SL+*
•Alloy axle with steel freehub body
•Carbon/alloy hubshell
•Hub with rotor weighs 680 grams

There doesn't seem to be any difference in the number of strain gauges or accuracy between the different wireless Powertap hubs. (+/-1.5% claimed accuracy for the newer Powertap hubs.) So far as I can tell there's no difference between the data accuracy whether it is recorded by a SL+, Pro+ or Elite+ hub.

If you were looking at SRM crank power meters then they have different numbers of strain gauges in different models. It makes the more expensive SRM models more accurate, adding something besides just different weights.

Powertap Accuracy (2005)
http://www.active.com/cycling/Articles/SRM_and_PowerTap__How_accurate_are_they_.htm

Powertap Accuracy (updated January 2011)
http://biketechreview.com/reviews/power-meters/61-power-meter-review?start=1

.


----------



## fux (Oct 21, 2006)

Hmm... You have a point there.

If I go for the Elite+ I have enough cash for a Chorus 11 cassett so I don`t need mess about changing when I swap wheels.


----------



## WR304 (Jul 9, 2004)

These are links to a few articles on Pez Cycling news about power meters. They're linked to from the active.com article in post #99 but you have to click through lots of webpages so I've put them together to make it easier if you want to read them.

Power Profiling
http://www.pezcyclingnews.com/?pg=fullstory&id=8983

Power Profiling 2
http://www.pezcyclingnews.com/?pg=fullstory&id=9001&status=True&catname=Toolbox

Fatigue Profiling as seen in links above (The Peakscoaching widget link doesn't work though...)
http://tt-training.blogspot.com/2010/05/fatigue-profiling-from-allan-coggan-v2.html

T-Mobile Pros 
http://www.pezcyclingnews.com/?pg=fullstory&id=3748

Power Meter Reasons (Lots of links to other articles in the text)
http://www.pezcyclingnews.com/?pg=fullstory&id=3660

Cycling Efficiency
http://www.pezcyclingnews.com/?pg=fullstory&id=850


----------



## rfxc (Oct 18, 2004)

*love my 39-53 quarq*

When they come out with a mtb 2x10 quarq, I'll scrape the cash together. I've considered removing the 53t chainring from my sram red/quarq crankset and running the 39t as a single front chainring with an xx rear. Should work for most of my midwest races, but not low enough for races in breck, methinks.


----------



## tg3895 (Mar 7, 2006)

Is the rotor a six inch rotor?


----------



## WR304 (Jul 9, 2004)

tg3895 said:


> Is the rotor a six inch rotor?


The MTB Powertap disc rotor is a standard diameter 160mm rotor. I don't think there are any compatibility problems using it with most brakes.

*Brake Rotor Width and Track*
I haven't got accurate calipers to measure the width but I think the Powertap rotor is probably 2mm wide which is the same as most popular brake rotors. It's surprisingly hard to find the standard widths of popular brake rotors. They don't seem to be listed anywhere but most are probably in the 1.8mm to 2.2mm range. There's some manufacturing variance between rotors of the same type too.

About all I could find was this discussion from 2006:
http://www.cyclingforums.com/forum/thread/353265/minimum-thickness-of-shimano-xt-rotor

Current Hope floating rotors are 2mm wide. 
http://www.hopetech.com/page.aspx?itemid=spg62&langID=470

The brake track on the Powertap rotor is 14mm deep. There are no clearance issues in that respect when used with a Hope Tech X2 caliper. The brake pads strike a litle bit low but it seems close enough. The picture below shows the clean brake track where the brake pads contact the Powertap rotor when used with a Hope Tech X2 caliper on my Specialized Epic.

I'm using a Hope Tech X2 brake and it's ok with the Powertap rotor. The lever feel is slightly different (with less movement) but power and modulation is fine. It isn't noticeably better or worse than the 160mm Hope floating rotor I used before when riding.

You'd think that such a bulky and heavy brake rotor would be completely straight but I found my Powertap rotor needed a little truing from new. After that the rotor has stayed round though.

Pictured below: The 14mm brake track of the 160mm Powertap disc rotor lines up fairly well when used with a Hope Tech X2 brake.


----------



## WR304 (Jul 9, 2004)

Here are some pictures showing the insides of a Powertap hub. It uses strain gauges to measure pedalling torque.

Strain Gauge
http://www.omega.com/literature/transactions/volume3/strain.html

Inside the Powertap hub there are two hub shells, one inside the other. Your power twists the two shells in relation to each other. You're supposed to use equal 3x spoke lacing for the wheel construction so that the hub twists evenly.

The picture shows the internal hub, known as the "torque tube". Strain gauges measure the deformation of this internal "torque tube" section of the hub. The strain gauges resistivity varies as you pedal. From these changes the torque in N.m can be calculated giving a power reading.

Pictured below: The Powertap "torque tube" internal section of the hub shell.

The bearings and axle inside the Powertap hub.


----------



## tg3895 (Mar 7, 2006)

WR304: Thank you for all the great info! :thumbsup:


----------



## WR304 (Jul 9, 2004)

When you see those pictures of the Powertap axle a lot of the components are all a push fit. You can pull most of the hub apart without needing any tools. There aren't any preload adjustments on the hub bearings either.

I've been trying to get rid of some lateral play which I think may be down to the non drive side axle end cap. There was enough play that the brake rotor could be pushed onto the brake pads easily.

The non drive side axle end cap is just an aluminium plug with two rubber o-rings on. From new this wasn't seated quite right so I pulled it out, put some waterproof grease on the o-rings and put it back in. This seemed to seat it a bit better. After tightening the DT RWS wheel skewer as tight as it would go there seems to be less play now.

Pictured below: The Powertap hub with its push fit non drive side axle end cap removed. The blue on the hub is marine grease that I hadn't wiped off.


----------



## WR304 (Jul 9, 2004)

I've been seeing a few videos on youtube where real time power output and speed gauges have been overlaid onto the recorded footage of cycling. You can watch the performance of the rider at the same time as the footage to see what they were doing.

Go Pro cameras
http://gopro.com/

The overlaid gauges showing the rider's power meter and speed data in real time were added to the video footage using Dashware software. I'd been wondering for a while how it was done.

http://www.chasecam.com/catalog/25

Here's a youtube video from a recent California criterium to give you an idea of what the real time gauges look like. 5:45 of the video is the best bit.

"2011 E4 Cherry Pie Criterium in beautiful Napa, CA"


----------



## WR304 (Jul 9, 2004)

WR304 said:


> Today's ride was all above sea level but if you do a ride where the altitude is below sea level then WKO+ interprets any altitude readings from Joule 2.0 below sea level as a fixed -3ft. Any altitude data below sea level is ignored.


This problem has been fixed with the newest version of WKO+ 3.0 Build 48. Altitude readings below sea level from the Cycle Ops Joule 2.0 head unit are now displayed on the graph. That's useful as it lets you see the altitude profile and elevation changes of the ride, even if the actual values are completely wrong still. I wasn't actually riding at -470ft on the graph below. The lowest altitude point should have been around sea level.


----------



## lassiar (Nov 11, 2010)

*Question*

For training purposes, does it help one's coach more to display power and cadence with or without zero averaging?


----------



## WR304 (Jul 9, 2004)

lassiar said:


> For training purposes, does it help one's coach more to display power and cadence with or without zero averaging?


Including or excluding zeros and the level of smoothing only affects the displayed figures on your power meter head unit. You'll normally include zeros in the power on the power meter head unit so that your figures aren't artificially inflated.

When you download the recorded data onto your computer and look at it in a program such as WKO+ 3.0 or Cycle Ops Poweragent the zero watts are automatically included in the power average. The data recording isn't affected by the settings in the head unit.

My display settings for the Cycle Ops Joule 2.0 head unit are:

Power Smoothing - 5 seconds
Power with zeros - Yes

Cadence Smoothing - 3 seconds
Cadence with zeros - No

Speed Smoothing - 1 second
Speed with zeros - Yes

*Zero Watts*
Knowing the times where you produced zero watts is something which can be one of the most useful aspects of having a power meter on the bike. Zero watts is a sign that you aren't pedalling. You typically want to be pedalling as much as possible throughout a training ride to get the most benefit from the time spent on the bike. It's worth trying to reduce the amount of time spent at zero watts if you can. It can be very eye opening just how much time you spend freewheeling during a ride, especially offroad.

Power data gives an idea of how much aerobic training benefit you may be getting from your mountain bike rides. The TSS, IF and average power from my mountain bike rides look terrible in comparison to similar duration rides on the road. You have to be very wary of this - riding offroad is fun and challenging but it can often end up counting as "junk miles" with little aerobic training benefit. That's where doing at least some road work comes in useful for building fitness. Having the power data to compare from both my on and offroad rides is very revealing in this respect. The difference is much greater than I thought it would be.:eekster:

Whilst riding on the road by yourself your power data will usually show pedalling nearly all the time. Apart from traffic lights and junctions you normally don't stop either. The only time there is much freewheeling is on descents, or if you momentarily stop pedalling to stretch your legs. You can concentrate on pedalling hard and maintaining a constant effort nearly all the time.

Riding offroad your power output can vary a great deal. There are often much larger amounts of time spent freewheeling or soft pedalling. On easy sections your power output is often very similar to riding on the road but on harder sections your power output can become much more variable as you have to react to the terrain. The limiting factor becomes bike handling rather than how hard you can pedal.

I've attached a short extract from today's ride showing 20 minutes riding along a rocky, deeply rutted farm track (It ended up on the dual carriageway so I had to do a u-turn and come back the same way.) It's a good example because I was having to concentrate on picking my way through the rocks and trying to avoid catching pedals on the edges of the ruts at the same time. You can see there was quite a lot of freewheeling and stop - start riding. Although I didn't do much hard pedalling on this farm track the sections where I did need to pedal often involved short sharp bursts to get over rocks or through mud.

This is the sort of situation where having recorded power data can be useful as it lets you evaluate how well you're riding different sections. If you spend a lot of time freewheeling and going slowly then that will cost you time. You can compare power data between rides to see just how much better you may be riding sections or whether different lines are faster also. 

Pictured below: Riding along a rutted farm track (U-turn midway). On tarmac this would have been pedalling constantly with no freewheeling.


----------



## WR304 (Jul 9, 2004)

WR304 said:


> (21 January 2011) - I replaced the batteries in the Powertap hub.
> ...
> The original batteries only lasted for approximately 60 hours of riding. I'm hoping that starting with fresh batteries means the hub will last a bit longer before they need replacing again.


This time the batteries lasted 83 hours of riding.

I've been getting low battery warnings from the Powertap hub all week so replaced the batteries again today. Hub Battery warnings flash up on the screen of the Cycle Ops Joule 2.0 head unit when they're getting low. My bike was broken for most of February so the Powertap didn't get used much in that month.

Something which I noticed today is that there appears to be corrosion and brown marks inside the Powertap hub. The marks definitely weren't there when it was new. So far as I can tell all the seals are in place and have lots of marine grease round them. It isn't obvious how the moisture got in there. Condensation perhaps? The hub electronics are working ok but it is a bit worrying.

Whilst I had the wheel off the bike I gave the freehub a service at the same time. It's been getting very loud and clicky so probably needed doing. Removing the Powertap freehub is completely tool free - take the skewer out, pull the cassette and the entire freehub just comes off in your hands. There are three pawls and they are held in place by a springy band (the recessed groove in the picture below). There aren't any springs and only one rubber seal. The seal isn't great so the pawls clearly look like they're going to need servicing frequently.

There was some light grease still but everything inside was quite dirty and one of the pawls was quite sticky. I cleaned it up and re-assembled the hub with Slick Honey grease as that's quite thin and what I had lying around. You don't want to use a thick waterproof grease because the pawls will stick. I was thinking about trying some Pedros Road Rage lube as that's what is recommended for Mavic Crossmax SL freehub pawls.

Apparently the recommended grease for the freehub is Kluber NB52 or Dupont GLP226 grease though so I'll probably get some of that for in future. 

http://www.bikeforums.net/showthread.php/104201-Special-grease-required-for-Powertap-conversion

http://www.saris.com/pdfManuals/308.pdf

Kluber NB52 Grease
http://www.klubersolutions.com/pdfs/Isoflex Topas NB 52.pdf

Dupont GLP226 Grease
http://www2.dupont.com/Lubricants/en_US/assets/downloads/krytox_gpl_106_206_216_226_K20067.pdf

With the freehub cleaned and regreased it's very quiet again. I think it's a lot like the Mavic Crossmax SL freehubs in that a quiet freehub means its working ok and noisy means the freehub needs servicing.

Pictured below: Powertap disc freehub pawls (cassette still attached) and the hub with the freehub removed.


----------



## WR304 (Jul 9, 2004)

WR304 said:


> one of the pawls was quite sticky. I cleaned it up and re-assembled the hub with Slick Honey grease as that's quite thin and what I had lying around.


My Powertap hub has done 3,100 miles (218 hours approx) in total and the pawls in the freehub are starting to stick, even after servicing it again. The freehub pawls use a metal band for spring tension and that metal band appears to be getting a bit baggy. There's still plenty of grease in the freehub but it doesn't sound right when you spin the wheel.

I'm hoping that I can get a replacement metal band for it instead of needing to buy an entire freehub body.

*Joule 2.0 History Errors*
I've been wondering why the history summary reports on the CycleOps Joule 2.0 head unit always seem to be completely wrong. Individual days are ok but the 2 week, 4 week summaries are way out. Looking at the History folder on the head unit it's clear that the head unit is writing multiple history files, even though I haven't pressed Stop and Save from the menu.:madman: If you look at the screenshot below this shows the contents of the Joule 2.0 head unit history folder.

On 03 May 2011 for example it wrote three history files. According to WKO+ the ride began at 10.26am and lasted for 2h11 total time. You can see when the files were created from the modified dates: One at 10.24am (presumably when I pressed Stop and Delete to reset the file at the start of my ride, although this _may_ have been user error by me as Stop and Save and Stop and Delete are next to one another in the menu.) One at 12.39pm (this would be the main file when I got home) and then another at 13.59pm (possibly when I connected the Joule 2.0 to the computer).

It isn't consistent though. On some days there's only one file created whilst on other days there are more than one file. My routine for using the Joule is the same each day (wake up hub, reset Joule 2.0 using Stop and Delete option, ride, save file, connect to PC later) so I'm not sure why it only happens on some days. It's clearly a bug of some kind. The times the duplicated files are created are very odd. 18.26pm on 28 April 2011 for example. It could be related to connecting it to a PC but I would most likely have downloaded the data from the unit well before that time.

Although these history errors are annoying they don't really affect the function of the unit. The summary information for each individual ride is ok. If I'm going to look at historic report summaries then I'll usually do it in WKO+ anyway.

Pictured below: CycleOps Joule 2.0 head unit history folder contents viewed from a PC. Note the multiple files with the same date. There should only be a single file created for each day.

CycleOps Joule 2.0 History file list showing multiple files with the same date (format is yyyy/mm/dd) and four week summary report showing how it affect the summaries as the unit shows an average speed of 4.7mph for the last four weeks. The power information is also affected making the summaries inaccurate.


----------



## vans380 (Sep 11, 2005)

Has anyone had to send their Powertaps back to Saris for rework?

I have an SL+ that I've had for a little over a year, only about 3500 miles, and recently it's started getting really flakey -- both the head unit and the hub. The head unit randomly fades in and out, and turns off occasionally. 

The hub is under-reporting toque. I was afraid I was really out of shape the last few rides! It's under-reporting by about 50-60 watts. I checked the offset value in the setup menu which is suposed to be in the range of 512, and it's reading 360ish. 

I called Saris today and they said because it is a few months over a year old I will need to pay $350 and send it back to them to have it rebuilt. This seems ridiculous to me, for such an expensive piece of equipment, to only get one season out of it before needing an expensive rebuild. I will not purchase another Saris product.


----------



## WR304 (Jul 9, 2004)

The batteries in the hub need replacing again. They lasted a little longer this time. 101 hours before the head unit began showing low battery warnings.

I'm hopefully going to be getting some spare Powertap freehub pawl bands and a spare set of pawls. I haven't got them yet though. 

The picture below is an example of the power output for a 4 minute interval that I did the other day. It was the 5th of a 6x4 minute set. This was outdoors riding the mountain bike but on the main road. If you do intervals on a turbo trainer then there will be less variation. Turbo trainer intervals tend to look much smoother with little variation in speed or power output. The orange gradient line shows that the road wasn't flat. I started off up a drag, went down a slope and then back up another drag for the final few minutes. The average cadence for the 4 minute interval was about 89rpm (the same average as for the entire 2h 39 ride).

If you look at the red heart rate trace there are two things to note. The first is that heart rate lags behind power output. I've been going flat out for 30 seconds+ before my heart rate begins to respond. The other is that power output during the interval changes even though my heart rate stays at a constant level. Towards the end of the 4 minute interval my heart rate rises, even though the power putput is dropping. 

The power output and speed traces show the difficulty of maintaining your interval pacing outdoors. The initial 30 seconds is a hard sprint to accelerate up to speed and then trying to maintain the pace for the remainder of the four minutes. I speed up to 25.9 mph on the downhill slope part way through but the power output falls away dramatically. This is probably the main thing that a power meter shows up. If you want to maintain your power output on downhill sections you have to shift up as many gears as you can as soon as the road drops in order to try and keep the power output constant.

If you hold the gear and pedal faster downhill your speed will increase but the power output will drop badly. Looking at the speedo or heart rate monitor and congratulating yourself on going faster is misleading (remember that heart rate lags behind). Heart rate may not drop even though you're no longer making a hard effort.

The final minute of the interval is a bit scruffy. You can see how speed and heart rate stays constant but the power output falls away. I was fading a little but if you look at the orange gradient trace the slope was flattening off slightly - another place where you have to be careful as in order to maintain the same power I should have tried harder and possibly changed up a gear.

Pictured below: Outdoor 4 minute interval power output compared to heart rate and speed.


----------



## WR304 (Jul 9, 2004)

Apparently CycleOps will be releasing a new Powertap G3 hub and also new cheaper CycleOps Joule and Joule GPS computers. There's no mention of whether there will be a MTB version of the Powertap G3 hub though.

http://velonews.competitor.com/2011...-meters-and-superlight-carbon-wheelset_178521

http://www.dcrainmaker.com/2011/06/first-look-at-new-cycleops-joule-and.html

*Powertap G3*
_"Coming in August, the PowerTap G3 is a 325-gram power-meter hub that has wider flanges but a smaller overall profile than previous PowerTap models. Selling for $1,299, the G3 houses the majority of its electronics, plus the battery and the antenna, in the replaceable end cap. The strain measurement components are still in the hub. When PowerTaps fail, typically it's the electronics that go. This new design allows a quick fix, as the company can mail out a new cap to customers."_

*Joule GPS*
_"Finally, in November, the company intends to have two new cycle computers, including a version with GPS. The $169 Joule features upgrades from the company's 2.0 - it's cheaper, smaller and easier to navigate - but with much of the same data (TSS, historic reporting, customizable dashboard and more). Its battery life is 300-400 hours.

The $269 Joule GPS is similar to a Garmin 500. There are no on-screen maps, just a record of your GPS data. "We are looking at this first and foremost as a computer for cyclists who train with power," Bartholomew said. "But we realize GPS data is a valuable feature, especially after the ride."

The Joule GPS has 18 metrics that are customizable on screen. The battery is rechargeable."_ *Velonews.com*

Pictured below: New CycleOps Joule GPS computer on left, CycleOps Joule on right


----------



## Markoj (Sep 26, 2008)

XCFred said:


> Has anyone had to send their Powertaps back to Saris for rework?
> 
> I have an SL+ that I've had for a little over a year, only about 3500 miles, and recently it's started getting really flakey -- both the head unit and the hub. The head unit randomly fades in and out, and turns off occasionally.
> 
> ...


I had the same problem with mine powertap after 1.5 years of usage.(it was the first version with steel 12mm axle)
Mine offset values were similar to your's, and I was getting readings about half the power then before.
Saris offered a full service for 350$, but I had i done here in Europe.

Now it's new version with alu axle 15mm, all new inside. Will see how long does it last.

I was hopping that somehow mine got damaged, but now I see you had the same problem :madmax:


----------



## WR304 (Jul 9, 2004)

WR304 said:


> This Youtube video is where *DC Rainmaker* tests the weatherproofing of several power meter head units: The Garmin Edge 800, Garmin Edge 500, Garmin Edge 705 and Cycleops Joule 2.0. They seem to fare quite well.
> 
> http://www.dcrainmaker.com/2010/12/feeling-lucky-water-immersion-tests.html


I've attached a picture of my CycleOps Joule 2.0 head unit after today's ride in the rain. I've been getting caught in heavy showers all week with lots of spray. This is the first week I've got properly drenched since March as it has mostly been warm and sunny this year. The last few months were warm and dry with very little rain.

The head unit has been filling up with water whilst riding (you can see it sloshing inside around the edges of the screen) and a lot of condensation has been forming inside the screen. The condensation is drying out now but after several hours it still hasn't cleared properly. The actual computer is still working but I'm very concerned about how easily water is getting in as it shouldn't be happening. It was fine all last winter in the rain but this week it doesn't seem to be weather proof at all.

I'm going to see if it's covered under warranty but it might be time for a different head unit.

Pictured below: CycleOps Joule 2.0 head unit showing the water and condensation in the screen after a wet ride today.


----------



## WR304 (Jul 9, 2004)

I got a Garmin Edge 500 to replace the old head unit. I've attached a picture showing it alongside the Cycleops Joule 2.0. The Joule 2.0 steamed up straight away today as it still has water in. I rode with both computers fitted today in order to compare the information. You can connect multiple head units to the same Powertap hub. The Cycleops ANT+ heart rate strap works with both head units also.

There are a few significant differences in terms of how the data appears when you download the ride files into WKO+ 3.0 from the Garmin Edge 500 and Cycleops Joule 2.0. I was hoping that the data would be identical but it isn't, even though the information came from the same Powertap hub. The main difference seems to be to do with how WKO+ 3.0 interprets starting and stopping from the different head units but there are some other things too. 

I'm not sure how useful the GPS track is. The GPS route on a map was fairly close to the actual route. In places on today's ride it was extremely accurate in open country with little cloud and no trees. Overlaid on Google earth you could even see where I had changed lanes in the run up to a roundabout and exactly where I had taken a shortcut along the pavement at one point! Under tree cover and in built up areas the track was jumping around a bit though.

Pictured below: Garmin Edge 500 and Cycleops Joule 2.0 alongside each other. You can customise the displays of both units. The screen of the Joule 2.0 is larger and has a bigger text size that is easier to read with multiple items displayed. Something had gone wrong with the heart rate strap. I'm fairly sure that I wasn't actually doing 152bpm whilst taking the photo!


----------



## wetpaint (Sep 7, 2009)

I would regard the Garmin's data as better than the Joule. On my road bike, I've used my PCVI and 705 together and the ride stats a basically identical, AP within 1-2watts (this only varies because I use autopause at 2mph on the Garmin), TSS is exactly the same, etc.

I'm not sure if the Joule autozeros, but the Garmins do, which is a quite nice.

For the Garmin HR straps, using some conductive get like this works well
performancebike.com/bikes/Product_10052_10551_1028575_-1_20000__400132


----------



## gnriden (Apr 18, 2006)

*SRAM 2x10 SRM*

I've been very happy with my PowerTap hub for a while now but with a new bike and a new rear axel standard i had to look for something new.


----------



## SpeedyChix (Apr 17, 2005)

gnriden said:


> I've been very happy with my PowerTap hub for a while now but with a new bike and a new rear axel standard i had to look for something new.
> View attachment 624985
> 
> View attachment 624986


Nice!! I'm holding out for the Quarq 2x10. 
What bottle cage / mount are you using on the seat post? Does it retain the bottle well in rough terrain? So many of them launch the bottle.
Thanks.


----------



## WR304 (Jul 9, 2004)

Here's the power data from Saturday's ride after it has been downloaded into WKO+ 3.0. This was a steady ride on the road. I had both power meter head units fitted running from the same Powertap hub on the same ride. There wasn't much stopping but I had to wait at traffic lights a few times.

I've manually cropped the ride files so that they cover exactly the same period with the start and end of the ride where I was stopped removed.

The Garmin Edge 500 had the "Autopause when stopped" option enabled and an identical wheel circumference to the Joule 2.0 entered. The Garmin Edge 500 uses the Powertap hub for calculating speed, distance and power which overrides any GPS data. They both record at 1 second intervals.

*"Elapsed Time" and "Time"*
When you press "start" to begin a ride on the Garmin Edge 500 there are actually two timers. You have "Elapsed Time" which will increase continuously until the file is closed and saved (press Stop once and then hold down Reset for 3-2-1-0 until the prompt disappears to save the file). "Elapsed time" continues counting up even if you press the "Stop" button and equals the total time that you were out.

There is also "Time" which is your moving ride time. "Time" is stopped and started by the start/ stop button. When using auto pause the "Time" timer stops and starts automatically whenever you stop (or the speed drops below a certain level). The total of "Time" is the amount of time you spent riding. If you were out for two hours but spent 30 minutes stopped then "Elapsed Time" would equal two hours whilst "Time" would equal 1h30. Your average speed would be calculated using "Time".

The CycleOps Joule 2.0 also operates in the same way when it is set to use speed for starting and stopping, although the "Elapsed Time" timer is hidden.

*WKO+ 3.0 Import*
When the data is imported into WKO+ 3.0 it treats the data from the two head units differently. This issue is a WKO+ 3.0 one as to how the information is interpreted. Stationary time is clearly identified with the CycleOps Joule 2.0. After 3 seconds of no speed the time is then shown in WKO+ 3.0 as being stationary until you set off again.

With the Garmin Edge 500 it's much more patchy. You need to be stationary for at least 20 seconds before WKO+ 3.0 identifies that you have stopped, even though the Garmin Edge 500's "Auto Pause" has stopped the timer shortly after you stopped. If you're stopped for less than 20 seconds then WKO+ 3.0 doesn't show any stationary time, which is what happened on Saturday as the lights changed quickly. The duration time in brackets shown for the CycleOps Joule 2.0 is total time whilst the time alongside is ride time. The Garmin Edge 500 data in WKO+ 3.0 shows all the 1h54m11s as ride time because all the stops were short.

The big difference between the two head units is in how they respond after you have stopped. When you begin riding again the CycleOps Joule 2.0 responds straight away so that there isn't a gap between setting off and it recording again. The Garmin Edge 500 however is much slower to begin recording again as there is a pause before it resumes. The Garmin Edge 500 also stops recording at one second intervals and you get a few data points covering longer 4 second + time periods immediately after starting. What happens is that you end up with a few data points of bad data for these sections with the Garmin Edge 500 every time you set off, adding in several seconds of high wattages that shouldn't be there every time you stop then start again. On Saturday for example my best 5 second power was actually shown as 7 seconds at 596 watts.

If you look at the best power outputs below you can see that the shorter duration power outputs are much higher for the Edge 500 than the Joule 2.0. This is where the bad data has been included in the totals giving inflated power outputs. Coming back into town I accelerated hard away from some traffic lights trying to stay with the traffic. The bad data from the Edge 500 when setting off from these sets of traffic lights has distorted the picture. What you can't see from the numbers is that several of the longer best power outputs are in different places in the ride because the additional high wattages riding back through town have moved the best sections also. You can clearly see this from the different maximum power outputs for the longer best power outputs.

If you disable Auto Pause then you don't get this bad power data on the Garmin Edge 500. The problem then is that the "Time" counter doesn't stop and WKO+ 3.0 doesn't flag any of the stationary time. Your short power outputs are ok but you end up with a lower average power and lower average speed than you would have otherwise because of all the stationary time added in.

*Other Differences*
The other differences that are worth pointing out are the differences in distance between the two head units (possibly related to starting and stopping), the missing Hub Torque channel from the Garmin Edge 500 and a difference in total ascent from the barometric altimeters of each unit. The altitude trace from the CycleOps Joule 2.0 is more detailed and sensitive to small changes in terrain than the Garmin Edge 500. Those are minor things though.

Pictured below: CycleOps Joule 2.0 and Garmin Edge 500 power data recorded from the same Powertap hub on the same ride. It shows the differences and errors that were introduced as a result of stopping and starting.


----------



## WR304 (Jul 9, 2004)

I had a look on the Wattage group as I was sure that other people must have had the same problem.

(You have to be signed in to view it)

http://groups.google.com/group/watt...7bb?lnk=gst&q=wko+garmin+500#c6b1bf2a77fe37bb

*Correcting Garmin Edge 500 Power Data in WKO+ 3.0*
Apparently WKO+ 3.0 can't handle the Garmin Edge 500's auto pause function. This is the problem which creates the bad data in the files. A workaround is to disable auto pause on the Garmin Edge 500 and leave the unit recording all the time, including stationary time such as stopping at traffic lights.

Your average speed and power displayed on the Garmin head unit post ride will be wrong but you can edit the recorded data in WKO+ 3.0 so that your recorded power and speed data will be correct with moving and stationary time identified. In order to do this you have to go through and manually cut out the stationary time.

Step 1: Import the Garmin Edge 500 .fit data file into WKO+ 3.0 using Device Agent.

Step 2: Open the ride graph with no smoothing and identify the first point in the file where you stopped (zero speed).

Step 3. Select the point two seconds after you stopped and holding down the left mouse button drag it to highlight in blue the period where you were stationary. Stop highlighting two seconds before the power and speed traces resume. You need to leave a gap of at least two seconds each side.

Step 4: Select Edit - Cut from the top menu. This will remove the highlighted stationary time, leaving a blank section in the graph.

Step 5: If you're happy that you have done it correctly save the file and then continue on to the next place where you stopped and repeat the process. If it's gone wrong then close the file without saving and re-open it to try again.

When you've finished the tidied file should clearly distinguish between the time that you were stationary and the total time that you were out. This lets you see how much time you were stopped at traffic lights / opening and closing farm gates etc during a ride.

Pictured below: The steps for correcting a Garmin Edge 500 data file in order to make it display correctly in WKO+ 3.0.


----------



## WR304 (Jul 9, 2004)

Here's a picture showing the post ride reports available on a Garmin Edge 500 when using a Powertap. These are the only two screens per ride, plus you can view the same for each manual lap.

As you can see there isn't much information. It doesn't tell you a great deal on the head unit beyond the basics. No Normalized Power, TSS, IF time in power zones etc. 

That doesn't really matter when you're downloading the data but as I had posted a few pictures of the CycleOps Joule 2.0 head units reports previously it's something to compare. 

My CycleOps Joule 2.0 has gone back under warranty now.


----------



## lassiar (Nov 11, 2010)

So what are the recommended Edge 500 settings for maximum accuracy when using a Powertap? I seem to have problems with grade and cadence not displaying accurately, and when I stop/start the timer, the Edge will sometimes perform weirdness, like failing to record anything other than time for a portion of the workout.

Also, how often should I perform a calibration of the Powertap? I use the calibration function on the Edge before every ride, but I don’t know the ins and outs of things like torque and auto calibrate.


----------



## WR304 (Jul 9, 2004)

lassiar said:


> So what are the recommended Edge 500 settings for maximum accuracy when using a Powertap? I seem to have problems with grade and cadence not displaying accurately, and when I stop/start the timer, the Edge will sometimes perform weirdness, like failing to record anything other than time for a portion of the workout.
> 
> Also, how often should I perform a calibration of the Powertap? I use the calibration function on the Edge before every ride, but I don't know the ins and outs of things like torque and auto calibrate.


I'm using the 2.80 firmware on my Garmin Edge 500.

The main issue with the Garmin Edge 500 seems to be problems caused when using the GPS "courses" feature to provide a route that you follow. The general advice seems to be that if you never use "courses" then you're less likely to have any data file corruption.

With a Powertap hub all the automatic features of the Garmin Edge 500 should be turned off. Here are my settings:

*System Menu*
Auto Power Down - OFF

*Bike Settings Menu*:
Auto Lap - OFF
Auto Pause - OFF
Auto Scroll - OFF
Start Notice - OFF

Data Recording 
Cadence - NON-ZERO AVG
Power - ZERO AVG
Recording Rate - 1 Second (although it doesn't matter with a Powertap because it automatically records at 1 second intervals)

Under the Named Bike Option -

Bike Details 
Wheel Size - CUSTOM and use a manual tyre circumference so that the GPS isn't involved. You have to be careful with a Powertap as the rear tyre compresses when you sit on the bike so the tyre circumference will be less than the uncompressed tyre circumference. Whenever you fit different tyres this needs changing. Don't leave it on auto.

ANT+ Spd/Cad - OFF The speed and cadence both come from the Powertap hub so there's no need for any additional sensors. This setting should be disabled.

ANT+ Power - YES 
Under the Calibration menu Auto Zero should be TICKED

*Garmin Power Meter Calibrate Screen*
There are two parts to the Powertap calibration menu on the Garmin Edge 500. The naming is slightly misleading as when you click on calibrate it isn't actually calibrating the Powertap. What it's doing is zeroing the torque offset of the head unit. By having Auto Zero ticked it will do this automatically when you stop pedalling during a ride. This is worth enabling as the Powertap hub's torque offset will often move during a ride. By repeatedly zeroing the torque offset to match this it should keep the power readings consistent.

In order to check whether the calibration of the Powertap hub is accurate you can use the bottom number on the calibrate screen. When you press down on the crank arm this number changes to show how much torque is being measured.

This Cyclepowermeters.com link explains how to carry out the calibration test. You'll need some weights to hang from the crank arm in order to check the readings.

http://www.cyclepowermeters.com/powertap-garmin-calibration-check-76-c.asp

*Garmin Edge 500 Display Settings Whilst Riding*
When riding there are three Power options available for the display - Power, Power - 3s Avg and Power - 30s Avg. This is the amount of smoothing on the power numbers. You need some smoothing because the power display is all over the place otherwise if you're viewing the unsmoothed power readings.

Power - 3s Avg is the one I have shown. It's still a bit jumpy (frequently +/-20 watts each way every time the display updates :madman: ) but that's the best option available. It can be a bit annoying when the display can't make up its mind how hard you're going. A 5 second display smoothing is easier to make sense of for pacing.

Cadence from a Powertap hub is virtual cadence. Without any smoothing on the numbers Powertap virtual cadence won't give you accurate readings. Whenever you see it giving you junk cadence numbers on the screen that's why. If you look at my ride history in post #126 you can see that it shows a maximum cadence of 177rpm, much higher than I actually pedalled at during that ride. All that virtual cadence is good for is looking at average cadence post ride.

Strange readings from the % grade display onscreen whilst riding is probably going to be a Garmin Edge 500 bug.

https://forums.garmin.com/showthread.php?t=13404

It's not a display item that I've had displayed to look at so far. I'll try it tomorrow. When I'm struggling up a hard hill in bottom gear I usually don't want to know steepness.:eekster: The elevation data recorded by the Garmin Edge 500 barometric altimeter appears roughly correct when downloaded into WKO+ 3.0 though. Compared to the CycleOps Joule 2.0 the amount of altitude gained over the same 1.5 mile climb is within 20ft or so. There's always going to be some variation with barometric altimeters so that's about as close as you'd expect.

Never pressing the start/stop button is the safest way to ensure that your data will be ok. Press the start/stop button once when you set off and only press it again when you finish the ride so that the timer runs continuously. I did that today and it got rid of any bad data this time. It takes a little effort going through the file in WKO+ afterwards and cutting out the stationary time but it's worth it to avoid any errors.


----------



## WR304 (Jul 9, 2004)

The Garmin Edge 500 has been working fairly well. It's survived several very wet rides and is still working. There haven't been any Powertap dropouts or strangeness either. I've been leaving the timer running and manually editing the data post ride. The % grade display on my head unit seems about right. It lags a little but the displayed gradients are close to what the actual hill steepness is.

One notable issue with the Garmin Edge 500 is that the rubber flap which covers the mini USB port isn't as tight as it was. Whenever you connect it to the computer the flap is pushed back hard each time by the USB cable. After less than a fortnight the rubber flap is already becoming a loose fit. The USB port itself isn't waterproof so you can't let it get wet as it will break the head unit. I'm going to have to start taping it in position so that the unit is sealed properly. They should have used a waterproof mini USB port like the Joule 2.0 really.

*Garmin Edge 500 GPS Trace*
WKO+ 3.0 doesn't have that many options for looking at GPS data. You can use it to adjust the altitude profile of the ride route or export the GPS trace into Google Earth. You can export either the entire ride or just individual sections. WKO+ 3.0 doesn't have the Garmin Connect option of being able to move your cursor over a particular point of the map to view power output, speed etc at that point. The GPS isn't really something that's a big priority for me but one thing I quite like doing is to look at the GPS trace of where I went in Google Earth and then trying to spot any alternative routes nearby using the satellite view and Googe Streetview. I've found a few nice byways doing that. You can see the lines running cross country on the satellite and then zoom in for a look at where they start and end.

The actual accuracy of the Garmin Edge 500 GPS trace is quite variable. It takes 30 seconds to a minute for the satellites to lock on at the beginning of a ride. A good tip is to turn the head unit on and leave it somewhere open to the sky before you start riding so that you don't have to wait for it. Riding in the UK the GPS accuracy is usually shown as being between 10-16ft in open areas. Under treecover the displayed GPS accuracy declines to 25ft+. It's ok for looking at where you went on a map but if you spend much time in woods then it doesn't seem that reliable. In woods I wouldn't trust the GPS speed reading to give any sensible information. A speed sensor looks like it's essential.

You can overlay multiple rides onto a single Google Earth map which gives an idea of how well the GPS works for tracking your position. It's normally quite good but sometimes the trace will go completely wrong with loops in the trace or veering off wildly, even though it's the same route as previous rides. The picture below is an example of how the GPS accuracy varies. This is the data from four seperate rides travelling along the same main road. All four of the blue GPS traces were travelling in the same direction (from right to left and riding on the left hand side of the road.) The yellow line overlaid is the position of where I would have been actually riding each time.

You can see how the blue GPS traces wobble around under the tree cover but as soon as I get out into the open countryside they become more accurate and follow the path of the road better. That's what it's like most of the time, apart from when it gets confused where the trace will go way off course.

Pictured below: Garmin Edge 500 GPS trace typical accuracy comparison between riding under treecover and in open countryside along a straight main road.


----------



## WR304 (Jul 9, 2004)

*Best Power Outputs In WKO+ 3.0*
By default it's quite hard to track your best power outputs in WKO+ 3.0. The dashboard summary shows your best best 1 minute, 5 minute and 20 minute power for each week/ month but that's all. If you want to see any other best power outputs then it means digging through individual files.

You can easily add a report to the dashboard which shows all your best power outputs though. I used the same periods that Poweragent displays, although you can use any period.

1. In order to create this open the dashboard in WKO+ 3.0. Click on the Options button at the top right of the screen. Options - Add a Chart to this Page - Performance Management Chart. This adds a new PMC chart to the dashboard.

2. Click on Options at the top right of the new chart and select Customize this Chart which will bring up a new dialogue box.

3. On the first General page change the title to "Best Power Outputs" and change the date range to "Custom thru today". I've used 01 Jan 2011 to today so that it shows all of this season.

4. Click on the Details tab and then delete all the existing items (CTL, ATL and TSB).

5. Click on "Add" and add the power periods that you want to view. The picture below shows how this appears. Type in the title for the power period (5 seconds, 10 seconds etc), Content is Mean Maximal, Channel is Power, Duration is the period that you want, Units are watts but you could also do w/kg.

On the right hand side Show Bests is how many points are displayed. If you wanted to see your 10 best 20 minute power outputs for 2011 then you'd enter 10 in this box. Choose a colour, Format - line, Symbol - square, Line Style - thin solid and that's the first one done.

6. Click "Add" again and repeat the process for each power period that you want to look at. The ones I have are: 5 seconds, 10 seconds, 30 seconds, 1 min, 2 min, 3 min, 4 min, 5 min, 10 min, 15 min, 20 min, 30 min, 40 min, 60 min, 90 min and 120 min.

7. Once you've finished click on Apply and the chart will be created. You can drag it around on the dashboard by holding down the left mouse button and dragging it to a new location.

Double left clicking on the chart on the dashboard makes it full screen so that you can see it better. By moving your mouse cursor over the individual points you can see what your best power outputs were and when they occurred. If you look at my chart below for example you can see that most of my power bests were in June and July 2011. There were hardly any power bests in January and February. When you have a full season of data to look at this chart will help to show where your best form was.

Pictured below: Adding a Best Power Output chart to the WKO+ 3.0 dashboard


----------



## WR304 (Jul 9, 2004)

In the Garmin blog post about their new pedal based Powermeter there are also some details about new features being added to the Garmin Edge 500 and Edge 800 head units. Apparently they're going to be updated so that they can display normalized power, intensity factor and TSS:

Garmin Brings Power to the People with Vector

_"*Get an 'Edge' on the competition:* For users already using a Garmin Edge® 800 or Edge 500 cycling computer, adding a Vector power meter will take their training to the next level. Not only will the Edge display total power, left and right leg power, and cadence, it will now also display in real-time the widely adopted power metrics from TrainingPeaks™: Normalized Power (NP ™), Intensity Factor (IF ™) and Training Stress Score (TSS ™). The Edge 800 adds a new interval summary page to enhance the power-based training experience.

"Vector's easy-to-own design has the potential to make power-based training more accessible and usable by a broader range of athletes," said Hunter Allen, founder of Peaks Coaching Group and widely regarded as a leading expert in training with a power meter. "In addition, by integrating the TrainingPeaks metrics of Normalized Power, Intensity Factor and Training Stress Score directly into the Edge head units for real-time display, Garmin continues to demonstrate a strong commitment to advancing power-based cycling tools." _*Garmin blog*


----------



## whybotherme (Sep 12, 2008)

WR304 said:


> In the Garmin blog post about their new pedal based Powermeter there are also some details about new features being added to the Garmin Edge 500 and Edge 800 head units. Apparently they're going to be updated so that they can display normalized power, intensity factor and TSS:
> 
> Garmin Brings Power to the People with Vector
> 
> ...


i really hope they start making axles for other pedals. i think i would spring for this setup x2 if they made a Crank Brothers pedal spindle....


----------



## WR304 (Jul 9, 2004)

The Powertap 160mm brake rotor works fine with 2011 Shimano M988 XTR Trail brakes. I'm still using the Hope mounting bracket from my previous Hope Tech X2 brakes and everything lines up properly without needing any tweaks.

The lever action and feel of the 2011 Shimano M988 XTR Trail brakes is quite different to my previous Hopes. I was actually quite nervous today whenever I had to do any braking. The XTR brakes are genuinely a one finger brake - all it takes is to gently tickle the brake lever and you're stopping rapidly. I was finding them quite grabby today though. That's probably down to new pads with old rotors, plus needing to practice with them more. The Hope Tech X2 brakes in contrast modulated nicely but always needed two fingers on the lever, along with quite a bit of hand pressure for big stops.

Looking at the braking deceleration from today's ride I wasn't really braking very hard (the maximum deceleration was only -2.39 m/s2 which is gentle) but that was largely because I was being cautious and trying to get a feel for where the brake's bite point was.

*Update:* The grabby brakes were down to the pads needing some time to bed in. After another few rides the initial bite when the pads first touch the rotor is feeling much smoother. It also helped spending some time with a tape measure making sure that the reach and lever travel was even between the left and right levers. The left hand lever (rear brake) was out a bit further than the right hand lever (front brake) as a result of my fiddling with the adjustments and not getting them quite the same.

The brakes are working well now and I've been gradually moving my brake points back towards the corners again. I always like to give it a while to build confidence before pushing too hard but they're feeling good so far. There currently isn't any brake squeal either, even riding in the rain today which is a nice surprise. My previous Hope and Avid disc brakes could always be relied upon for plenty of brake squeal in the rain.

Pictured below: Shimano M988 XTR Trail brake caliper with Powertap brake rotor.


----------



## laudares (Aug 5, 2011)

Looks like Cycleops is already selling its new version of Powertap Pro for mountain bikes:
(I can not post any links since I'm new to the forum, but go directly to Cycleops site).

I'm curious wether someone has had any experience with the new model and would share thoughts about it. Something I would like to know is wether this model enjoys the architectural improvements announced by Cycleops, like the separation of the "electronics" from the hub structure per si, thus allowing for servicing the system without having to send the entire wheel back to them.

Regards,
Fernando


----------



## WR304 (Jul 9, 2004)

laudares said:


> Looks like Cycleops is already selling its new version of Powertap Pro for mountain bikes:
> (I can not post any links since I'm new to the forum, but go directly to Cycleops site).
> 
> I'm curious wether someone has had any experience with the new model and would share thoughts about it. Something I would like to know is wether this model enjoys the architectural improvements announced by Cycleops, like the separation of the "electronics" from the hub structure per si, thus allowing for servicing the system without having to send the entire wheel back to them.
> ...


The new 2012 mountain bike Powertap hub is the Powertap Pro. There doesn't seem to be an MTB version of the lightweight 2012 Powertap G3 hub. In UK pricing from cyclepowermeters.com the 2012 Powertap Pro disc hub is £825 GBP (plus an extra £39 GBP for the brake rotor), which is £120 GBP less than the previous MTB Powertap disc hub cost.

http://www.cycleops.com/en/products...page_images.tpl&product_id=618&category_id=22

The 2012 Powertap Pro still uses the old style heavy hub body but according to this Bikeradar.com article the internal electronics within the 2012 Powertap Pro hub have been updated. There would be enough room in the hub for the Powertap G3 electronics module to fit so it might be replaceable also.

_"The PowerTap Pro is meant for those with cost in mind when buying a power meter. While considerably heavier at roughly 425g, it offers the same features that offers a ± 1.5% accuracy and the same style external transmitter, which comes with the same ease of serviceability as the G3 model. All of this, however, is packaged in the larger old style hubshell." _*Bikeradar.com *

CycleOps New PowerTap G3 And Pro, Head Units And Wheels - BikeRadar

If you look in the specifications on the Cycleops site it says that the Powertap Pro hub uses 1 x CR2032 battery, rather than the 2 x 357 batteries that the older Powertap hubs use so it must be slightly different internally. CR2032 batteries are what the Powertap G3 hub uses too. The Powertap G3 electronics module would fit easily into the space beneath the cover of the Powertap Pro hub. It's mostly empty space under there in the old style Powertap hub. You can see the battery and electronics of the G3 hub in these DC Rainmaker pictures. :

DC Rainmaker: First look at the new CycleOps Joule and Joule GPS, PowerTap hubs, PowerCal, and VR software

Pictured below: 2012 Powertap Pro MTB disc hub

Powertap G3 electronics module


----------



## WR304 (Jul 9, 2004)

CycleOps have finally released a new firmware update for the CycleOps Joule 2.0 head unit. Apparently it adds a new screen but could be a little problematic updating to the new firmware.

Weight Weenies • View topic - joule new firmware 14.072 update

My suggestion for trying to do the update via the Poweragent software updater would be to make sure you have the head unit connected to a Windows XP pc first. If you try and do the update connected to a Windows 7 64 bit PC the intermittent connection issue is sure to make the firmware update fail.

My CycleOps Joule 2.0 that filled with water was replaced under warranty but I haven't used the new one. It's sitting in a box as the Garmin Edge 500 has been ok.

Something to remember with the Garmin Edge 500 is to regularly clear out the contents of the "activities" folder from time to time (every week or so). If you have too many ride files in there it really slows down the time it takes to load ride histories.


----------



## WR304 (Jul 9, 2004)

.


----------



## WR304 (Jul 9, 2004)

*Coffee King (CK)* pointed out that wheelbuilder.com now have a Powertap 142x12mm axle conversion kit available. The conversion kit allows you to use your existing Powertap hub with newer bikes such as the Specialized Epic and Trek Superfly 100 which have 142x12mm thru axle rear dropouts.

Once converted the Powertap hub can also still be used with standard 135mm QR rear dropouts by simply swapping the end caps.

Wheelbuilder PowerTap MTB 142mm x 12mm Axle Conversion

There isn't any mention of warranty on the product page so it would be worth checking what implications this has before ordering. I'd guess that swapping the axle will probably void any existing warranty on your Powertap hub.

Pictured below: Wheelbuilder.com 142x12mm axle Powertap hub conversion kit


----------



## WR304 (Jul 9, 2004)

My Wheelbuilder.com 142x12mm Powertap conversion axle arrived a while ago but I hadn't got round to doing it until now. My new bike is getting close to being ready so I decided it was worth swapping the axles over.

*Bearings*
The first thing to note is bearing sizes. The Powertap MTB disc hub original bearings are:

Non Drive Side bearing: 6802 2RS 15 x 24 x 5 mm
Original Drive Side and freehub bearing: 6902 2RS 15 x 28 x 7 mm (three bearings, one in the hub and two in the freehub)

The conversion axle comes with an Enduro 17 x 28 x 7 mm bearing included. It also comes with 2x 142mm end caps and a single 135mm non drive side end cap (you re-use the original 135mm drive side end cap). I used SKF bearings as replacements for the other bearings.

Replacing the bearings in the Powertap hub is quite straightforward. Tap out the old cartridge bearings and press new ones in. For the 17mm inside diameter drive side bearing we used a headset press to make sure it went in square. Everything went well initially - speed readings, torque offset etc were all fine on the hub after replacing the bearings. The wheel bearings and freehub span freely when not fitted in a frame.

*Axle Left-Right Free Play*
It was only when the wheel was mounted into the frame and the skewer tightened down that it became clear there was an issue. As the wheel skewer was tightened the freehub was binding, so that the wheel became a fixed wheel. It became apparent that there was roughly 0.6mm of left-right free play in the axle after the hub bearings had been pressed in. Not good.

After taking it apart, checking the axle width measurements and that the bearings were pressed in properly it's not clear where this 0.6mm of play is coming from. The conversion axle width length and assembly appear to be correct. Both the bearings were pressed fully home. I'm wondering if possibly the Powertap hub had left - right play with the original axle too (I don't remember any but didn't check before pulling it apart). You wouldn't notice with the original axle as the endcaps and skewer clamp everything down so that the freehub is held in place against the drive side bearing.

*Freehub and Axle Design*
The big difference between the original axle and conversion axle is the drive side design where the freehub body sits. On the original 15mm Powertap axle the drive side bearing slides onto the axle and then a sleeve goes inside the freehub body. The end of the sleeve presses against the drive side bearing and acts as a spacer, so that the freehub body is always kept roughly 0.5mm from the drive side bearing. The drive side bearing is pressed into the hub so the freehub body is unable to move inwards towards the bearing, even if there was play in the hub axle.

The conversion axle is different. It uses a 17mm inside diameter bearing slid onto the axle and then the freehub sleeve is machined into the axle as a step. This means that the drive side bearing and freehub body will still have a 0.5mm gap between them (when the drive side bearing is pressed against the axle shoulder and the freehub body is put in place). This gap is empty space however (rather than the 0.5mm of solid metal sleeve that holds the freehub body and drive side bearing apart with the standard axle). So long as there is no axle play the machined step holds the freehub in its correct position.

Because there's 0.6mm of free play in the axle as you tighten the wheel skewer it pushes the hub axle across towards the non drive side however. Once that happens the machined step that should hold the freehub body in place is out of position and the freehub body is free to move inwards, resulting in it binding on the hub.

With the original axle design this problem wouldn't occur. The reason that it's been done I think is because the axle has to be much thinner in order to take a 12mm skewer through it. With a 12mm inside diameter and 15mm outside diameter the axle would be weaker than the thicker original Powertap axle so the additional material reinforces the axle, making it less likely to snap.

My hub isn't sorted yet. This conversion might have been smoother starting with a brand new hub. The bearing shoulder to shoulder measurements of the two axles are identical so I'm wondering if the problem is with the hub itself. Powertap hubs are made of seperate parts so maybe something had stretched or slipped over time? My 2010 Powertap hub had done 10,343 miles/ hours 698 hours from new, although the original bearings were all still smooth and in good condition. The plan now is to try putting a 0.6mm spacer on the inside between the axle shoulder and non drive side bearing as a way of removing the axle play. I'm hoping that will sort it.

Pictured below: Powertap internal parts and widths compared to Wheelbuilder conversion axle


----------



## jared_j (Jul 15, 2009)

*Rotor options*

What are the rotor options? Do you have to use their branded rotor with the correct # of holes, or are there other options?


----------



## morganfletcher (Jul 22, 2005)

jared_j said:


> What are the rotor options? Do you have to use their branded rotor with the correct # of holes, or are there other options?


You have to use their two-piece rotor. It has a different number of holes, larger center bore and the aluminum carrier is not in plane with the rotor.

Morgan


----------



## WR304 (Jul 9, 2004)

WR304 said:


> After taking it apart, checking the axle width measurements and that the bearings were pressed in properly it's not clear where this 0.6mm of play is coming from. The conversion axle width length and assembly appear to be correct. Both the bearings were pressed fully home. I'm wondering if possibly the Powertap hub had left - right play with the original axle too (I don't remember any but didn't check before pulling it apart).


Here's a picture confirming that the problem is with my Powertap hub, rather than the conversion axle or bearings. The hub width (inside of bearing to inside of bearing) is 52.69mm. Both axles are 52.07mm wide (shoulder to shoulder), explaining why there was play. I think it's very likely that the original Powertap axle must have had some left - right play in also.

Looking at the conversion axle I think that the way to fix the issue would be to put a 0.6mm spacer between the non drive side axle shoulder and bearing, making the axle width match the hub width. In order to make sure that it isn't possible for the axle to move I think a spacer is needed inside the non drive side endcap of the hub too. This takes up all the free space inside the non drive side endcap that the axle is currently able to move into. Essentially making the axle longer.

The additional spacer in the endcap would neutralise any left - right axle play once the entire hub is tightened down. The non drive side endcap presses against the bearing so the axle would be unable to move out of position once the wheel skewer has been tightened. The changed design of the conversion axle means that it's crucial for the axle to stay in exactly the right place. The original Powertap design is much more forgiving of any differences.

Pictured below: My Powertap hub width 52.69mm (inside of bearing to inside of bearing) doesn't match the width of the axle 52.07mm (shoulder to shoulder), resulting in the 0.6mm of left -right play which is causing the freehub to bind once the skewer is tightened.

The design of the conversion axle means that there's a gap between the non drive side axle and endcap. If there's any play in the axle (as with my hub and its 0.6mm of left-right play) this gap allows the axle to move into the endcap and out of position.


----------



## WR304 (Jul 9, 2004)

It's been a few weeks but I finally have my 142x12mm thru axle Powertap hub working.

It spent a few weeks at my mate's factory waiting for the new 0.6mm spacer washer to remove the play. That spacer was made and installed last week to correct the bearing width problem. Everything seemed good with free spinning bearings and no binding from the freehub, except that the torque tube zero offset was reading 369 when I checked it. Anything beyond a zero offset of 512 +/-5 means the hub has an issue.

Because I've been using a Garmin Edge 500 head unit and my 2010 Powertap SL+ MTB disc hub had an older firmware version (meaning that it only displays the Powertap hub's ANT+ ID, rather than the hub's torque zero offset) I hadn't checked the zero offset since last summer when my Joule 2.0 broke. There's a chance my 16 month old hub may have had an issue which I wasn't aware of, even before I started pressing new bearings into it.

*Powertap Service*
Fortunately, the Powertap UK service centre is just down the road so I took it there to be fixed. It was quite interesting to see how they did it. The Powertap hub is in two parts. You have the hollow shell and hub flanges, but then literally everything inside the hub is part of a single unit which unscrews. Broken torque tube unscrewed - in the bin - new torque tube fitted.

For pressing the 142x12mm axle conversion bearings in and out of the torque tube they used a vertical press. A combination of supporting spacers underneath the torque tube and a flat spacer against the bearing made sure it went in square. With all the correct tools it was done easily.

For assembly they recommended using a layer of Contralube 770 Connector Lubricant on all the internal electronics of the hub, especially on the connection where you plug the battery pack into the hub. I've always put waterproof grease around the seals but not on the connector itself. After riding in very wet conditions or with a lot of condensation they recommended taking the hub's black plastic cover off to let it all dry.

Contralube 770 Connector Lubricant : Lubricants & Butane Gas : Maplin Electronics

Once the hub had been assembled it was then calibrated accurately and adjusted using a custom wheel jig which had a weight hung from a metal bar integrated into the jig. The new torque tube began with a zero offset of 500 and after calibration was adjusted to the correct 512.

I'm very grateful to them for sorting out the hub out whilst I was there. I'd been expecting to have to leave it. My Powertap hub is now at the wheelbuilder being built into a 29" rim to go on my new bike.

Pictured below: Contralube 770 connector lube for the Powertap internal electrical connections


----------



## WR304 (Jul 9, 2004)

My 2012 Specialized Epic 29er is finally up and running. The Powertap hub with its 142x12mm conversion axle seems to be working fine so far. Just like any other Powertap hub but with the correct spacing for the frame.

I had it built into the original Roval Control 29 rear rim that came with the bike for now.

The picture below shows the updated calibration screen on my Garmin Edge 500. The 2010 hub internals were an older firmware version and the Garmin Edge 500 only displayed the hub's ANT+ ID before. With the new hub internals the Garmin Edge 500 shows the zero offset of the hub in the calibration screen. Much more useful. A value of 512 is the normal calibration you'd expect if your Powertap hub is working properly.

Pictured below: Garmin Edge 500 Powertap calibration screen. Powertap hub installed in 142x12mm 2012 Specialized Epic 29er frame


----------



## WR304 (Jul 9, 2004)

The converted 142x12mm Powertap hub has been working well. No problems at all with it so far. The data from it seems comparable to all my previous data. 

It's quite interesting doing a direct comparison to see how my new 2012 Specialized Epic 29er compares with my previous 26" 2010 Specialized Epic. I swapped nearly all the parts over so that apart from the frame, fork and the bigger wheels they're the same bike.

My mountain bike is my only bike nowadays so it gets used for road rides as well as offroad. One issue that I discovered today is that the longer wheelbase of the Epic 29er makes it harder to draft a roadbike closely when riding in a paceline. I was out for a ride by myself when some guys from the road club caught me up. They'd been out on the clubrun and were heading home. It was into the wind so we were riding through and off in a paceline. 

One thing stood out immediately. When riding with other riders you automatically fall back into the patterns that you've learnt over all the years of road racing and riding. That means staying tight to the rider in front for the maximum slipstream effect. Only with the Epic 29er the front wheel sticks out so far you can't get that close to the bike ahead. My front wheel was almost touching the rear wheel of the rider in front but he was still a long way away.:eekster: This was also repeated in the other direction. I could see that when a rider was behind he was tending to overlap wheels in order to try and get closer. 

The graph below is an 18 minute extract from the ride showing riding in a paceline on the road. The highlighted areas show where I was working hard on the front, and then recovering in the slipstream of another rider. You can see how I'm putting in a big effort to maintain the speed, but only for 20-60 seconds each time before the next rider rotates through so I get a rest.

Aerodynamic issues are more exaggerated using a mountain bike. You can't miss how much less effort it takes for a road or time trial bike to travel at the same speed. I was lucky on Sunday that it was into the wind and only about 21mph average speed. When the speeds get up to near 30mph you have so much aerodynamic drag on the mountain bike that trying to come through for a turn on the front is almost a waste of time. It's ok following wheels but as soon as you pull out from the rider in front at 30mph it's like hitting a wall. If you look at the graph of yesterday's ride you can see that where the blue speed trace was highest at 30mph I made sure I was sitting in. I only came through once we were going up the slope and the speed had dropped. Something I've learnt from getting dropped repeatedly in the past.

If you look at the end of each work section you can see that the rotation was generally fairly smooth without too many big speed or power jumps. There aren't too many big spikes at the end of each work section. What you can get sometimes if a rider goes through too hard at the beginning of a turn is that they open up a gap and the rider who's been on the front has to sprint to try and get onto the wheel. That shows up in the power graph as a big spike at the end of each turn. It's either a sign of bad technique by the rider going through, or a sign that you're tiring. If you're trying to work with other riders it's better to go through just slightly faster than the lead rider, hold your line so that you don't chop their front wheel and allow them to ease across into your slipstream.

Pictured below: Riding in a road paceline.


----------



## litany (Nov 25, 2009)

WR304 said:


> With the new hub internals the Garmin Edge 500 shows the zero offset of the hub in the calibration screen. Much more useful. A value of 512 is the normal calibration you'd expect if your Powertap hub is working properly.


I have the old disc hub (I've been riding it for a few years) and I just updated my hub with the ANT+ updater so it would work with my Garmin 500 and on the same screen you show I have "Current Calibration -9031" which isn't even close to 512. I don't think this is my hub ID, it shows a different number for that something around 52000 I think.

Should I be worried about my torque tube?


----------



## litany (Nov 25, 2009)

So I've been sitting at home thinking about my -9031 number, hoping that it's not supposed to be saying 512 since that seems like a big difference...

I went and hung a 20lb weight from my pedal with the crank parallel to the ground and the chain in 22f 34 rear and on the calibration screen on the edge 500 for torque it said 25.62. If I calculate what it should say using this:

torque = M g L Nr / Nf,

where M g = weight of bucket with water, L = crank length, Nf = teeth on front ring, and Nr = teeth on rear ring.

I get 213lb in which is within about 6% what the powertap is showing. This is fine as I was going for a ballpark number anyway. My measurements were pretty sloppy, it was a 20lb kettle bell still in it's packaging which my park tool fish scale said weighed 19lb 12oz and my bathroom scale said was 20.0lb, additionally I didn't use a level on the crank arm (small angle approximation and all...meh)


----------



## WR304 (Jul 9, 2004)

litany said:


> I have the old disc hub (I've been riding it for a few years) and I just updated my hub with the ANT+ updater so it would work with my Garmin 500 and on the same screen you show I have "Current Calibration -9031" which isn't even close to 512. I don't think this is my hub ID, it shows a different number for that something around 52000 I think.
> 
> Should I be worried about my torque tube?


What was your torque offset before you updated the hub to ANT+?

Because you have an older hub the Garmin Edge 500 probably isn't going to display anything useful in the calibration field. It needs a Powertap hub with one of the latest firmware versions for the Garmin Edge 500 to be able to show the Powertap hub's torque offset.

Do you know anyone with an ANT+ Cycleops head unit? (either a LYC or Joule). If you can pair that with your hub then the Cycleops head unit should show what your hub's torque offset is.


----------



## litany (Nov 25, 2009)

WR304 said:


> What was your torque offset before you updated the hub to ANT+?
> 
> Because you have an older hub the Garmin Edge 500 probably isn't going to display anything useful in the calibration field. It needs a Powertap hub with one of the latest firmware versions for the Garmin Edge 500 to be able to show the Powertap hub's torque offset.
> 
> Do you know anyone with an ANT+ Cycleops head unit? (either a LYC or Joule). If you can pair that with your hub then the Cycleops head unit should show what your hub's torque offset is.


I didn't check before converting it to ANT+, I didn't know how or even think to do it. Since I dont have anything but Garmins I ended up following these instructions I got from Saris for using my yellow CPU to get the zero offset.

Here are the steps to get the calibration reading on your Wireless PowerTap w/ yellow CPU:

1. Ensure you have transmission by spinning the wheel. The transmission icon on the top left of the CPU should be present. If you cannot get transmission, re-learn the hub ID, check the batteries of hub and CPU, and battery holder in the hub.

2. Once you have transmission, press and hold MODE and SELECT until you enter the Setup screen. This screen will display after "clr".

3. Using the SELECT button, navigate to the "t" on the middle line, then press MODE

4. Press MODE three more times so you arrive at the 3rd test screen

a. Top Line = The Offset (difference between Middle and Bottom lines)

i. Ideally this is "0". If it is not "0", push and hold SELECT until it becomes "0"

ii. If this does not go to "0" you may need a new wireless CPU

b. Middle Line = Raw Torque Value

i. 500 - 524 is the acceptable range, meaning your hub is reading with +/- 1.5% accuracy

ii. If it's anything outside this range, you may need us send your hub/wheel for repair

1. We will need to issue you a Return Authorization # before you can send it in

c. Bottom Line = Calibration of CPU

i. 500 - 524 is acceptable range (same as middle line)

My values were

Top: 0
Middle: 492
Bottom: 492

Waiting to see what Saris has to make of these numbers.


----------



## WR304 (Jul 9, 2004)

492 is a bit low. One thing to try would be changing the batteries again as that can affect the torque offset. Saris can manually recalibrate the hub which might be enough to sort it out.

If the hub is a few years old there might be a problem though. If you look at the picture in Post #106 that's the torque tube part of the Powertap hub. It's a one piece unit without much that can be easily replaced. If there is something wrong with the torque tube then they might recommend a new torque tube. If they decide to do that then the best bet is to ask for all the hub internals to be replaced at the same time in order to eliminate any other possible issues. 

I think that my Powertap hub might be drifting out of calibration. It started off at 512 at the end of February 2012, it was up to 518 a few weeks ago and reads 523 today. The problem with that is it raises the question of whether the power values the hub is reporting are accurate. Have I really been setting personal power bests for the last few months or not? 

Today was my best 20 minute FTP test result ever, including 10 min 40 seconds at an indicated 285 watts average power for the climb section of the route. I equalled my best FTP test time up the hill from last year (10 min 41 seconds average power 267 watts 15 June 2011). Considering that the June 2011 time was set using slick tyres and I was using knobbly tyres today it is possible that I was putting out more power today.

On the climb today I saw a red top in front a few bends ahead, thinking it was a bike I dug in to try and catch them, only to realise it was a runner! I was going flat out and it took some doing to catch them. I was doing 7mph and they were only 1-2 mph or so slower than that. I passed them before the top, just. It was the final minutes of the FTP test and I was puffing like a steam train by that stage.:eekster:


----------



## litany (Nov 25, 2009)

Yeah, Saris basically said it's not a huge deal but it is out of spec. They said currently it should read low, about 15W at 200W and about 60W at 400W. So it sounds like if your calibration is low it will read low, if it's high it will read high (which makes since because it's apparently the "raw torque value"). They told me I could spend some money to send it in and have the internals upgraded to SL+. They will basically replace everything inside the hub, axles, bearings, and torque tube for a pretty reasonable price. Apparently the new hub that just came out has SL+ internals but has a cheaper, heavier shell which allowed them to lower the price from $1600 to $1100. 

I changed the batteries when I did the ANT+ upgrade. Maybe I will fiddle with it some more but probably not because it's pretty delicate in there and I don't want to break anything. So apparently I have the 2.4 hub, and I've upgraded it to 2.4+. Considering this hub has thousands of miles on it I'd say it has held up pretty well. At least as well as any other bike parts do. 

Congrats on the PR! I love passing people out on the trails, especially when I'm doing a FTP/TT day! Some of those trail runners are pretty darn quick though


----------



## WR304 (Jul 9, 2004)

The Powertap torque tube replacement cost is surprisingly reasonable. It's a lot cheaper than if you were to buy a whole new Powertap hub anyway.

The Powertap hub's torque offset figure is affected by temperature too. It might be worth checking what it is at the start of a ride, going out riding for a few hours and then checking it again to see whether it has changed.

My Powertap hub started off at 523 this morning (11c air temperature), after 1h30 riding it had changed to 520 (17c air temperature). Auto Zero on the head unit should allow for this though. Whenever you stop pedalling on a Powertap hub with Auto Zero enabled it should automatically re-zero the torque offset figure to keep the figures consistent.

(With a Quarq Quattro you need to have Auto Zero enabled and also remember to manually back pedal during the ride in order to zero the torque offset from time to time.)

Looking at the first splits from today, where I was riding on the road, against similar split times from last year the power figures seem comparable. It's something that I'm going to keep an eye on though. eg:

21 April 2012 (new Powertap Torque Tube): Distance 13.4 miles, Time 49m 52sec, Average Speed 16.1 mph, Average Power 183 watts, Max Power 488 watts, Normalized Power 205 watts

25 August 2011 (old Powertap Torque Tube): Distance 13.4 miles, Time 50m 28 sec, Average Speed 15.9 mph, Average Power 181 watts, Max Power 477 watts, Normalized Power 207 watts

One thing that seems to have genuinely boosted my power output was to change my cycling shoes. I've used Specialized BG Expert carbon soled shoes since 2008 but got some new Giro Code shoes at the beginning of March 2012. The Giro Code shoes have a very stiff Easton EC90 full carbon fibre sole and are basically a road shoe with some tread on the bottom. I've been setting new personal power bests across the board since then.:eekster: 

The chart below shows my top 10 best power outputs for 2011- 2012. The highlighted section is after I switched to the new shoes. You can see how I've been managing new personal bests from the number of dots in that area at different time durations. 

Giro Code shoes


----------



## WR304 (Jul 9, 2004)

I've mostly been doing offroad rides recently but yesterday I managed to wake up early enough to get out on the road club run. I haven't got any slick tyres for the Specialized Epic 29er yet so it was still on Specialized Ground Control 29x2.1" tyres, but pumped up to 50 psi for road use.

The usual format for the club rides is to do a few hours and then stop at a cafe. I rode over, met up with the club, rode with them until the cafe stop and then headed home on my own to avoid too much sitting around. 

Total ride:
4 hours 50 minutes ride time, 78 miles, average speed 16.1mph, average power 182 watts, Normalized Power 213 watts 

Riding to club meeting place:
39 minutes ride time, 10 miles, average speed 15.9mph, average power 177 watts, Normalized Power 197 watts

Riding with the Road Club: 
2 hours 2 minutes ride time, 38 miles, average speed 18.9mph, average power 200 watts, Normalized Power 237 watts

Riding home through the hills:
2 hours 9 minutes ride time, 30 miles, average speed 13.6 mph, average power 167 watts, Normalized Power 188 watts

I've attached a few extracts from the ride below as they're quite a good example of what to look for. When riding with a group on the road you gain a large benefit from slipstreaming behind other riders. So long as you can stay in the slipstream it takes far less effort than it would to travel at the same speed if you were riding by yourself. Even on a mountain bike this can be enough that you find yourself riding at low intensities for much of the ride. Looking at just the club ride section of the ride I spent almost 30% of the time in the lowest "active recovery" power zone. On group rides it's very easy to end up riding gently and not as hard you'd expect. Fine as a social ride but not much good as a training ride. This is something that a power meter shows up very well.

This particular ride was quite mixed with several harder sections ridden at higher intensities. I was yo yoing on and off the back at these points. If you look at the ride data you can see why. The most efficient way to ride in a group is to always hold the wheel of the rider in front. So long as you can hold the wheel you get a big benefit from slipstreaming. As soon as a gap opens however there's no longer any slipstreaming benefit and it's much harder until it can be closed again. 

The graph below shows one point where I was temporarily dropped towards the end of the club ride section. It illustrates how much of a difference slipstreaming makes. I'd been following wheels, trying quite hard at 207 watts average power but staying in contact until a series of short but steep power climbs. Despite producing my best 1 minute power of the ride (360 watts) I was gapped slightly as the climb steepened. The consequence of that small gap opening was that it then took 5 minutes chasing flat out at 300 watts to eventually close the gap again. When I got back into the slipstream my average power output dropped to 152 watts due to being behind the other riders again. If I hadn't let that gap open then I wouldn't have needed to put in the big effort to catch up again. 

Once the club stopped for their cafe stop I headed home by myself through the hills. I was feeling a little tired by this stage. It was getting colder, beginning to rain and there was a headwind all the way back. This is where the power meter came in useful for pacing, helping to parcel out my remaining energy to hopefully avoiding blowing up completely. 

On the climbs I concentrated on trying to keep my power output in the Endurance/ lower end of the Threshold power zones without ever going too high. Seeing the power output going over 250 watts or so was a sign to change down a gear and back the pace down. If you're just riding on perceived exertion it's easy to feel comfortable and end up going harder than you want to, especially if the gradient changes and you put in short bursts. In this case I knew that there were several climbs coming up and it was nearing the end of a long ride so I concentrated on just turning the gear over. The third climb was probably a little too gentle but it was raining fairly hard by that point and I was concerned about cramping up.

The graph also has a few clear signs that I was tiring. If you look at the flatter sections between climbs the power output trace is very intermittent. All those drops are where I was only pedalling for 1-2 minutes at a time before getting out of the saddle and freewheeling. When you see lots and lots of close pauses towards the end of a ride it indicates that I was a bit saddle sore and uncomfortable on the bike. If I was feeling fresh and still going well there would be far fewer pauses and fairly constant pedalling. On a typical long ride I'll really lift the pace for the last 30 minutes to an hour also but it doesn't happen here. Another sign that I was tired and just trying to get home.

Pictured below: Power zones for just the 2 hour Road Club run section. Despite it being hard I still spent almost 30% of the time in the Active Recovery power zone

The altitude scale on the two graphs below is different. The club ride was mostly flat so I've zoomed in the altitude scale on the club ride graph in order to show the small bumps where I was dropped. The hills on the second graph are longer more sustained climbs. The Power and Speed traces on both graphs have the same scale.

An extract from during the road club run. I'm gapped on a short power climb. Without being in the slipstream it's a hard chase to get back on.

The final two hours riding home by myself after leaving the road club at the cafe stop. I'm feeling tired and use the power meter to gauge my pacing up the climbs so that I don't push too hard and blow up.


----------



## WR304 (Jul 9, 2004)

This interview with Uli Schoberer (inventor of the SRM power meter) makes some interesting comments.

A chat with Uli Schoberer - Slowtwitch.com

If you're using a Cycleops Joule 2.0 head unit then this post about a new firmware for it might be useful. They still don't appear to have fixed the Windows 7 issue fully though.

JOULE 2.0 AFTER 100km (Page 2): Triathlon Forum: Slowtwitch Forums

_"Hi everybody,

Sorry for all the issues and lack of posting a response.

To summarize we do acknowledge the issues discussed in this thread and others for some time now. To recap the issues they are:

1. Distance resetting at random when an ANT+ speed sensor or combo spd/cad sensor is used
2. Windows 7 recognizing Joule 2.0 or taking a long time to recognize
3. 8.8 torque multiplyer (note this was a display issue only and did not effect power measurement or display)
4. Battery drain

Issues 1, 2 and 3 are being addressed with firmware currently in beta. Testing thus far has gone well and we plan a full release in the next couple weeks. If you would like access to the beta version please contact Eric via email at [email protected] The beta version of firmware is 14.082. Please note that despite our best efforts the only way to improve issue #2 is by disabling the SD card functionality.

Regarding battery life, the life expectancy depends on use and charging cycles (the number of times you plug it in to recharge regardless of how much juice the battery has when you plug it in). If you are not getting the expected 20+ hours replacement batteries are available from our customer service team, give them a call at 1-800-783-7257.

Again, we apologize for the issues these bugs have caused and are working hard to eliminate them.

Jesse Bartholomew 
CycleOps Product Manager 
Saris Cycling Group" _


----------



## WR304 (Jul 9, 2004)

Garmin have finally released their firmware version 3.00 power update for the Garmin Edge 500 to add TSS/NP/IF etc.

There are some details about the update here:

DC Rainmaker: Garmin releases Edge 500 update, adds TSS/NP/IF & more

From the comments the best way is to download the firmware update through the Garmin webupdater software.

Garmin | WebUpdater

If you delete any old activity ride files that were stored on the device then it will update faster also.

I've updated my Garmin Edge 500 to firmware version 3.00 now. It seems to be working ok but I haven't ridden with it yet.


----------



## litany (Nov 25, 2009)

Thanks for letting us know. 

It's too bad the Garmin doesn't record torque, it would be nice to see. I mean, might as well right?


----------



## WR304 (Jul 9, 2004)

litany said:


> Thanks for letting us know.
> 
> It's too bad the Garmin doesn't record torque, it would be nice to see. I mean, might as well right?


It is odd that the Garmin Edge 500 doesn't record the "Hub Torque" channel like the Cycleops Joule 2.0 head unit does with a Powertap hub. It still has a "Crank Torque" channel recorded though. That hasn't changed with the new firmware.

The main benefit of the new Garmin Edge 500 firmware for me is that they've added a 10 second average power display option for whilst you're riding. If you use 10 second average power then the power figure display is much more stable and less jumpy, making it easier to pace yourself with.

What you can do to see how this changes the displayed numbers is to make a new page: Settings - Bike Settings - Data Fields - Select a page. On the page add just the four different power options Power, Power-3s Avg, Power-10s Avg, Power-30s Avg. When you ride that allows you to see how the different smoothing options affect how jumpy the power numbers are. The 10 second average power is what I'll be using from now on.

TSS, NP and IF aren't really things that I look at whilst riding. Garmin have missed an opportunity there as the Garmin Edge 500 post ride reports are still exactly the same as before (see Post #126 for what they look like). I was expecting them to be more detailed after the update. It means that if you want to view TSS, NP and IF on the Garmin Edge 500 you'll need to make an additional display page, in order to look at them before you save the ride file.

My Powertap hub's calibration is quite confusing still. It started off at 512 late February with the new Torque Tube fitted. Over the next few months it drifted all the way up to 523. I checked it this morning with the new firmware before setting off and it had returned to 512 again. After 3 hours riding in 25-30c temperatures today I checked the calibration when I got home and it was down to 506.


----------



## XC Dawg (Oct 20, 2005)

WR304 said:


> One of my big reasons for getting a power meter was for comparing ride intensity and trying to evaluate whether I was tired or not.
> 
> The problem being that after a few weeks of solid riding my exercise heart rate response would be very low, even though I felt good. I'd end up ignoring the heart rate monitor most of the time as I simply didn't believe what it was telling me.
> 
> ...


Hey WR304, thanks for this as well as all your other posts in this thread about Powertaps, I just recently started doing a structured training program myself and have been wondering about getting a power meter.

Your detailed analysis and pictures are very helpful


----------



## XC Dawg (Oct 20, 2005)

Also, can anyone tell me what's a fair price for a used Powertap disc laced to a so-so wheel? I'm looking at the wheel alone with no head unit.


----------



## WR304 (Jul 9, 2004)

I've ridden with a Powertap since the end of October 2010 now. As the amount of historic recorded information that you have increases it becomes possible to see some "big picture" trends emerging. Looked at year on year the Powertap data shows whether you're improving, where you're improving and also when you're improving. From that you can then look at the aspects in more detail if needed.

*Overview*
Compared to the same period of time in 2011 my overall power output for all miles ridden at 22 June 2012 is up by around 1.8% so far this year. (01 Jan 2011 - 22 June 2011, 252 hours, average power 165 watts, NP 187 watts / 01 Jan 2012 - 22 June 2012, 336 hours, average power 168 watts, NP 191 watts).

A useful chart to make for this type of summary in WKO+ 3.0 is a custom Periodic Chart on the Chalkboard. Add Hours, Miles, Average Power and Normalized Power as data series and then set the Days Per Point to 999 before clicking Apply. What you can then do whenever you want to see your totals is change the dates in the Calendar screen to the period you're interested in and click "Update Chalkboard". You can then go to this chart on the Chalkboard page and quickly read off the period totals from the individual points.

*Mean Maximal Power Year On Year*
Looking at my Mean Maximal power outputs for 2011 compared to 2012 there hasn't been an even across the board increase. At short durations (up to about 2 minute efforts) I'm only equalling, or even slightly below my power bests from last year. From 2 minutes up to around 2 hours I'm consistently around 3-5% higher for my best efforts this year when compared to 2011.

Where the power meter really shows an improvement is over longer rides though. This is what I've generally been concentrating on in 2012. 3-4 hour rides done on consecutive days. At 3 hours duration my 2012 best power output is 7.04% higher (average power 185 watts 2011, average power 199 watts 2012) and at just under 5 hours it's 9.5% higher (average power 164 watts 2011, average power 182 watts 2012). Knowing this is useful as it shows what sort of fitness improvements I'm gaining from the particular workouts that I've done. Doing longer rides has helped with endurance and sustained work rates but hasn't made me a better sprinter. Being able to see the results helps to target the workouts towards what you're aiming for.

*Predicting Best Fitness During The Year*
Along with this it's possible to look at where the best power outputs were during the year. If you take my best power outputs chart and change the date range to include both 2011 and 2012 then a clear pattern emerges, showing where my best form is likely to be. This pattern is one that I've always suspected from previous years but the power data confirms it. There are two clear groupings of power bests for me in these particular years. From the start of March 2011 through to the end of July 2011 and then from the start March 2012 through to today (22 June 2012). The rest of the year is very sparse with few power bests being achieved. This is an indication that with my normal riding schedule I can expect to be going well during March to July but then not quite as strong for the rest of the year.

Pictured below: My Mean Maximal Power Outputs 2011 (dashed line), 2012 (yellow line) showing how I haven't improved equally across all time durations. Where the yellow line is higher than the dashed line it shows that I have managed a higher average power for that duration this year than last year. The main improvement has been over longer endurance rides. At very short durations I'm about the same as last year.

My personal power bests 2011 - 2012. The highlighted sections with the greatest concentration of dots during the year are where I'd expect to have the best fitness.


----------



## WR304 (Jul 9, 2004)

I did a 1 hour time trial as an FTP test today. This was on an out and back flat route on the road but quite windy and raining. It was mostly crosswinds apart from lap 5 which was straight into the wind. Towards the end of the ride I had to get through some traffic lights and over a few roundabouts which is why the power and speed traces jump around.

What I like to do when reviewing a ride such as this one is to break it down into smaller segments. I'll add in a lap marker every 10 minutes as a way of seeing how well my pacing worked. I was aiming to keep my power output between 231 and 269 watts, my "Threshold" power zone for the entire ride. As you can see from the graph and split times I didn't quite manage it. I started out strongly for the first 20 minutes but my power output sagged a little mid ride, falling below the target power zone for laps 3 and 4. 

If you look at the orange altitude trace you can see that this 20 minute segment is slightly downhill. Keeping your power output high downhill is hard to do. If the speed seems fast enough it's easy to fall into the trap of not going as hard as you could. I should probably have pushed a bigger gear there. 

By looking at the ride in sections it shows where the weak points were. If I'd done better and managed to sustain the early tempo mid ride then my average power output could potentially have been nearer to 240 watts than the 232 watts that it actually was. Because I can see what went wrong this time I know what to work towards the next time that I do the same ride again. 

If you were to try and look at it purely on average speed without seeing the power output change then it would harder to identify the problem. Speed is heavily influenced by factors such as wind and slopes. Looked at using average speed lap 5 (slightly uphill into a headwind) would appear to be a weak spot, even though I know from the power output that I was trying hard there.

On the way back I lifted the pace for the final 15 minutes, trying to make it count and setting my best power outputs of the ride.

Pictured below: 20 mile time trial FTP test on a flat route. The yellow dotted lines indicate the upper and lower edges of the target power zone that I was aiming for. With one minute smoothing applied the graph gives an idea of how well I stayed within it.

Individual lap split detail


----------



## WR304 (Jul 9, 2004)

It's been very wet here since April. It seems like almost every ride has been in a torrential downpour but my Powertap hub is still going strong. 

What works well is to put sta-lube marine grease around the rubber seals of the Powertap battery compartment, along with on the non drive side bearing. It makes sure that the water will stay out.

Search results for "SL3120" | CRC Industries

That's more than can be said for the rest of the bike. The rear suspension pivot bearings had to be replaced after just three months as they were creaking and in a bad state.:skep:

If you're out riding in the rain then this will affect the Garmin Edge 500's barometric altimeter. The small holes underneath the unit used for the altimeter must fill with water. This often means that your altitude trace and climbing totals will be completely wrong on wet days.

What you can do in WKO+ 3.0 is to correct the altitude using GPS. Right click on the range bar for "Entire Workout" and select "Fix Elevation Profile Using GPS". This will bring up a screen showing the before altitude profile. Choose "Ground Control" from the drop down and click Begin. Once the progress bar reaches 100% a yellow line showing the updated GPS altitude will appear which can then be applied, changing the altitude trace. For longer rides the GPS correction is much quicker if you create some smaller ranges and then correct each range individually. The GPS correction can sometimes get stuck if you try and do the entire ride in one go.

The GPS trace isn't as accurate as the barometric altimeter would normally be so you'll see more spikes. For dry rides I'll leave the original Garmin Edge 500 altitude trace untouched. I'll only use GPS correction if it's been wet and the altitude needs to be fixed. If there are any big spikes on the graph after you have used GPS correction then these are GPS errors. Note the time of each one and change the graph view to Raw Data. You'll see the incorrect altitude number there. Type in a new number close to the adjacent ones to remove the altitude spike before saving the file again.

Pictured below: sta-lube marine grease

Using GPS in WKO+ 3.0 to correct the altitude trace of a wet ride where it has gone wrong.


----------



## WR304 (Jul 9, 2004)

Making yourself ride slowly enough on recovery rides is something that I'm quite bad at. I'm more likely to end up riding at close to my normal pace, even when it's supposed to be an easy day. 

Recovery rides are one place that pacing yourself with a power meter is often at its most useful. If you usually ride hard or fairly hard on most rides then you get used to that level of exertion. Your body grows to expect to be riding at or above a particular preferred exertion every ride. By strictly riding to the power meter's display on recovery rides it helps you to avoid getting carried away and riding harder than you intended.

The graph below shows my power outputs during today's recovery ride. After a few solid weeks riding I'd had two days completely off the bike beforehand and had considered having today off too, until a gap in the rain appeared. After quickly getting ready I set off but it was immediately obvious my legs were feeling very tight and there was no point pushing it. 

I ended up doing a 1 hour active recovery ride targeting the 0-141 watt range. If you're trying to do an active recovery ride be prepared for how slow it feels. On this flat ride I averaged 116 watts and had an average speed of only 13.4mph. 

Any short uphills will see spikes in your power output so you have to gear right down. You can see on the graph how the blue speed trace is as low as 7mph on the short uphills as I shifted down through the gears to the 33x32 in an attempt to keep the power output low. Even then I was riding in the Endurance power zone (142-192 watts) for most of the short uphills. There are also a few spikes where I went way above the top of Endurance power zone but as soon as I realised I sat up and backed off again.

Pictured below: Using a power meter for a 1 hour active recovery ride to try and keep the power output low.


----------



## WR304 (Jul 9, 2004)

Here's what a crash looks like. If you're ever looking at a power file an extremely sharp deceleration is often a sign that it was a fall. A bike is fairly limited in how quickly it can slow so an abnormally fast stop to stationary is something to look out for.

On Saturday afternoon I was coming up to a roundabout on the main road. I was doing around around 16mph. I paused, went for a gap in the traffic but as I accelerated hard my right SPD pedal came unclipped. My right foot flew forwards into the front wheel, breaking several spokes and jamming between the fork leg and wheel. The bike flipped straight over and I landed hard on my left shoulder and left thigh, still attached to the bike by my right foot.

Fortunately there was no car directly behind as I ended up lying on the ground in the middle of a main road with my right foot trapped between the wheel and fork. Some people stopped and forced the front wheel backwards to get my foot out and I slowly crawled out of the road to lie down on the grass verge. 

I've attached the power data just before I fell off. I hardly slid at all as the bike went straight over and came to a rapid halt. You can see from the sharp drop in the speed trace how sudden it was. 

I've attached a picture of the front wheel too. The hard carbon sole of the Giro Code cycling shoe mostly protected my foot from being crushed so it's bruised but the wheel came off worse. You can see where the shoe went through the wheel and broke the spokes.


----------



## litany (Nov 25, 2009)

WR304 said:


> *Coffee King (CK)* pointed out that wheelbuilder.com now have a Powertap 142x12mm axle conversion kit available. The conversion kit allows you to use your existing Powertap hub with newer bikes such as the Specialized Epic and Trek Superfly 100 which have 142x12mm thru axle rear dropouts.
> 
> Once converted the Powertap hub can also still be used with standard 135mm QR rear dropouts by simply swapping the end caps.
> 
> ...


Saris told me that having wheelbuilder do the conversion did not void the warranty on the hub. So that's good to hear. I asked Saris if they offered 142x12 or if they could convert it for me and they said no, go to wheelbuilder so they are clearly 100% aware of what wheelbuilder is offering. According to wheelbuilder they actually worked with Saris on some of the hubs, providing input on flange dimensions and things like that.

So I basically did the same thing as you with my powertap for my new bike. After sending it to Saris for new internals I took the SL+ 2.4 Disc, powertap hub straight to wheelbuilder.com to get it converted to 142x12. However after getting the wheel built up I realized I hit a big snag. The rivets on the rotor (between the carrier and the rotor itself) rub the frame on my Pivot Mach 5.7 Carbon's integrated post mount. Apparently this is a problem on some carbon Specialized frames (the epic I think wheelbuilder said?) So I'm kind of surprised you didn't run into this as well but it looks like your frame doesn't have the integrated post mount so that's probably why. I'll call wheelbuilder and saris tomorrow to see if they have a solution.




























Honestly this rotor carrier seems like huge overkill. It's a rear rotor so it doesn't get that much force, it has 8 bolts holding it on the hub at a pretty large radius with a 4mm thick piece of what looks like aluminum. By comparison the front rotor I'm using is also a two piece 160mm but by formula and the bolt circle diameter for the six bolts is much, much smaller and the aluminum is only 2mm thick. Realistically this all shouldn't matter much as the friction between the rotor and the hub will be holding it in place rather than a shearing load on the bolts themselves. My *biggest *challenge here is going to be trying to mill this thing perfectly flat so the rotor remains true when mounted to the hub. I plan to remove 1-1.5mm of material.

To clarify I won't have to mill down the whole face of the rotor carrier, just the circled area. The hub is actually machined out between the bolt holes so there is no need to cut between them.


----------



## litany (Nov 25, 2009)

WR304 said:


> The Powertap torque tube replacement cost is surprisingly reasonable. It's a lot cheaper than if you were to buy a whole new Powertap hub anyway.


Yeah, the cost for this is probably one of the biggest advantages the powertap has. Honestly the powertap is the most cost effective power meter you can get. Compared to the quarq and the pedal based meters it's cheaper to buy, and new internals are also cheaper so it's cheaper to maintain. I really hope SRAM doesn't ruin Quarq's customer service.


----------



## WR304 (Jul 9, 2004)

litany said:


> So I basically did the same thing as you with my powertap for my new bike. After sending it to Saris for new internals I took the SL+ 2.4 Disc, powertap hub straight to wheelbuilder.com to get it converted to 142x12. However after getting the wheel built up I realized I hit a big snag. The rivets on the rotor (between the carrier and the rotor itself) rub the frame on my Pivot Mach 5.7 Carbon's integrated post mount. Apparently this is a problem on some carbon Specialized frames (the epic I think wheelbuilder said?) So I'm kind of surprised you didn't run into this as well but it looks like your frame doesn't have the integrated post mount so that's probably why. I'll call wheelbuilder and saris tomorrow to see if they have a solution.
> ...
> My *biggest *challenge here is going to be trying to mill this thing perfectly flat so the rotor remains true when mounted to the hub. I plan to remove 1-1.5mm of material.


My current bike is a 2012 Specialized Epic Expert 29er. It has a post mount 140 rear disc brake fitting but the rear triangle is M5 alloy, rather than the carbon fibre rear triangle of the S-Works Epic. There's plenty of clearance between the brake rotor and frame and it didn't need any modifications to fit. You can just about see it if you zoom in the picture in post #144.

If you only need 1-1.5mm of clearance then I'd file down the inside of the frame post mount until it doesn't catch on the brake rotor. Removing that small amount of material isn't going to affect the frame structurally. It's also in a place where any filing isn't visible.

If you grind down the brake rotor that could cause two issues.

- If you don't take exactly the right amount off then the brake rotor will be out of true to begin with, making it virtually impossible to align the rotor to stop it rubbing.

- By moving the brake rotor 1-1.5mm inwards, away from the frame mounting points, you could find that there isn't enough left-right adjustment of the brake caliper to centre the brake caliper on the rotor. There isn't much you can do if that happens.

I would do a photo showing the clearance on my frame but after crashing three weeks ago I still can't move around enough to even get to my bike. My left leg isn't working at all and my shoulder is a mess. It's looking like at least another three weeks of almost total bed rest.


----------



## litany (Nov 25, 2009)

So saris does actually have a solution to this! Apparently when they converted my hub to a 15mm axle that shifts everything over and they mill down the carrier .5mm to compensate. They forgot to do this for mine and sent me a new rotor that was milled down. Looks like 1mm was taken off, seems to fit fine now!

Sorry to hear about your injuries, what a bummer. Get better soon!


----------



## WR304 (Jul 9, 2004)

litany said:


> So saris does actually have a solution to this! Apparently when they converted my hub to a 15mm axle that shifts everything over and they mill down the carrier .5mm to compensate. They forgot to do this for mine and sent me a new rotor that was milled down. Looks like 1mm was taken off, seems to fit fine now!
> 
> Sorry to hear about your injuries, what a bummer. Get better soon!


That's interesting to hear.

Was it Saris or Wheelbuilder who modify the rotor? There doesn't seem to be anything about a different rotor on the wheelbuilder site?

It's the sort of thing you really need to know before buying.

It's taking a long time for my left leg to settle down. After four weeks lying in bed or propped in front of the TV on a recliner chair I'm getting a bit tired of being stuck indoors. On the plus side it's better to be at home recovering than as a hospital inpatient for once.

Still, it will make for a good graph showing how much detraining and loss of power output there can be from inactivity when I do finally get back on a bike again. At the moment I've no idea when that will be though.


----------



## litany (Nov 25, 2009)

WR304 said:


> That's interesting to hear.
> 
> Was it Saris or Wheelbuilder who modify the rotor? There doesn't seem to be anything about a different rotor on the wheelbuilder site?
> 
> ...


Saris is the one who does it. When I sent my hub in they put all new internals on it. Even a new free hub. Apparently this change brought the axle to 15mm, this is different from the conversion wheel builder does. Saris are supposed to mill down the rotor carrier when they do this upgrade. The wheelbuilder conversion doesn't seem to change the offset at all. In fact they said it only works with the 15mm axle and not the old 12mm axle the hub had before it was upgraded to the new (current for the new hubs they came out with a few months ago) internals.

Hopefully you can ride again sooner rather than later!


----------



## WR304 (Jul 9, 2004)

litany said:


> Saris is the one who does it. When I sent my hub in they put all new internals on it. Even a new free hub. Apparently this change brought the axle to 15mm, this is different from the conversion wheel builder does. Saris are supposed to mill down the rotor carrier when they do this upgrade. The wheelbuilder conversion doesn't seem to change the offset at all. In fact they said it only works with the 15mm axle and not the old 12mm axle the hub had before it was upgraded to the new (current for the new hubs they came out with a few months ago) internals.
> 
> Hopefully you can ride again sooner rather than later!


Thanks for clearing that up. So the rotor spacing issue is down to starting off with the older 12mm axle version of the Powertap hub shell and rotor. Fitting the newer 15mm axle Saris internals changes the rotor spacing slightly.

That would explain why I didn't have that problem. My 2010 Powertap hub came with 15mm axle internals so the rotor spacing wouldn't already be correct and not need adjusting.


----------



## laudares (Aug 5, 2011)

> Replacing the bearings in the Powertap hub is quite straightforward. Tap out the old cartridge bearings and press new ones in. For the 17mm inside diameter drive side bearing we used a headset press to make sure it went in square. Everything went well initially - speed readings, torque offset etc were all fine on the hub after replacing the bearings. The wheel bearings and freehub span freely when not fitted in a frame.

Thanks for your post, very informative! I'm having trouble removing the freewheel/cassete body. I've removed the end caps but the cassete body seems to be locked in place. Is there anything else that should be done besides pulling/forcing the cassete body out ? It does look straightfoward on the youtube videos covering the road model but i wonder if there is an additional step fot the MTB model ?

Thank you,
Fernando


----------



## litany (Nov 25, 2009)

laudares said:


> > Replacing the bearings in the Powertap hub is quite straightforward. Tap out the old cartridge bearings and press new ones in. For the 17mm inside diameter drive side bearing we used a headset press to make sure it went in square. Everything went well initially - speed readings, torque offset etc were all fine on the hub after replacing the bearings. The wheel bearings and freehub span freely when not fitted in a frame.
> 
> Thanks for your post, very informative! I'm having trouble removing the freewheel/cassete body. I've removed the end caps but the cassete body seems to be locked in place. Is there anything else that should be done besides pulling/forcing the cassete body out ? It does look straightfoward on the youtube videos covering the road model but i wonder if there is an additional step fot the MTB model ?
> 
> ...


Which one do you have? For mine you just pull the free hub off but it can be quite hard. One thing I do (dt Swiss told me to do it when I was having trouble with my 240 free hub) was to leave the cassette on and hammer it off from the back. I made sure not to just hit one spot but to do more of a star pattern. I set a big Allen key against an old cassette and hit it with a rubber mallet.


----------



## laudares (Aug 5, 2011)

Hello Litany, my model is the original powertap MTB disc model, which looks like the SL+ but with the proprietary rotor connections on the non-drive side. I've got it second-hand and altough it looks great the bearings look really finished.
I did tried your technique - i only hit a few times in different points, but it looks stuck. Being in Brazil, I'm not considering sending it to Saris. Should i try to hit it harder or might be something else holding the freebody in place ?
Thanks, Fernando


----------



## WR304 (Jul 9, 2004)

laudares said:


> > Replacing the bearings in the Powertap hub is quite straightforward. Tap out the old cartridge bearings and press new ones in. For the 17mm inside diameter drive side bearing we used a headset press to make sure it went in square. Everything went well initially - speed readings, torque offset etc were all fine on the hub after replacing the bearings. The wheel bearings and freehub span freely when not fitted in a frame.
> 
> Thanks for your post, very informative! I'm having trouble removing the freewheel/cassete body. I've removed the end caps but the cassete body seems to be locked in place. Is there anything else that should be done besides pulling/forcing the cassete body out ? It does look straightfoward on the youtube videos covering the road model but i wonder if there is an additional step fot the MTB model ?
> 
> ...


Old Powertap road hubs had locknuts and also needed an allen key. I don't think that the older versions came as a MTB Powertap disc hub though.

http://www.cycleops.com/pdfManuals/Archive/Comp/308.pdf

Do your hub's endcaps and axle look like the ones in post #106 and #113? If so, the hub should be the toolless model. With the endcaps removed the freehub should pull off by hand. If you leave the cassette attached it gives more leverage to pull the freehub body off.


----------



## laudares (Aug 5, 2011)

Hello Liyany, WR304,
you're right, it was just that the free hub body was REALLY stuck: installing a cassete and hammering on it did the trick. There was corrosion in the steel spacer inside the hub body which kind of glued it in the hub's axle. I've bought this unity second hand and although it was shiny I believe it has never seen any internal maintenance. I've ordered new bearings and will rebuild it before starting to use it.
Thank you guys for your comments, they were really useful.
Fernando


----------



## WR304 (Jul 9, 2004)

laudares said:


> Hello Liyany, WR304,
> you're right, it was just that the free hub body was REALLY stuck: installing a cassete and hammering on it did the trick. There was corrosion in the steel spacer inside the hub body which kind of glued it in the hub's axle. I've bought this unity second hand and although it was shiny I believe it has never seen any internal maintenance. I've ordered new bearings and will rebuild it before starting to use it.
> Thank you guys for your comments, they were really useful.
> Fernando


It sounds like it's had a hard life. If the rest of the hub is in that bad a state are the electronics still in working order? If there's a torque tube issue then it will need to go back to Saris to be repaired which is quite expensive.

Have you checked the powertap hub's torque offset to see if it's still close to 512? With an older hub you'll need a little yellow computer or Cycleops Joule 2.0 to be able to display the figure. Garmin Edge head units only display the torque offset for newer firmware versions of the Powertap hub.


----------



## litany (Nov 25, 2009)

WR304 said:


> It sounds like it's had a hard life. If the rest of the hub is in that bad a state are the electronics still in working order? If there's a torque tube issue then it will need to go back to Saris to be repaired which is quite expensive.


For $350 saris will replace all the internals and the free hub body. It's expensive yeah, but considering you basically get a brand new $1600 hub back for $350 it's not bad at all. As a result you can keep a power tap hub running for years without too much continued expense. Hopefully my quarq doesn't end up being more expensive...


----------



## ultreia (Nov 2, 2010)

Hello,

I want to dismantle completely the hub to try to repair myself, there is any way to get out the torque tube?

Thank you!


----------



## TritonBill (Mar 12, 2010)

I have power tap hub wheelset for my road bike but I don't have it on my 2012 Cannondale Flash 29'er. Would you suggest sticking with Powertap and just getting a back wheel and/or buying cranks with power built in for my Cannondale?!

I've been accumulating and training by power now since July. I use WKO+ 3 software and so far have found it very interesting. All my workouts are super specific and I have enjoyed it but this type of training program also makes it tough to ride with others when I am doing very specific workouts in varous training zones! WR304 and others... I may have to pick your brains now and then on the MTB side with power if I go there.


----------



## TritonBill (Mar 12, 2010)

One things I've noticed on my PowerTap G3 hub is that the cadence it gives me seems to be pretty consistent as well as the mileage when I'm on a trainer. If anything it seems a little under represented when riding on the trainer. Often times I do what feels like a 1 hr ride and what feels like the equivalent of a 15.5 - 17 mph pace and it will calculate it as a 14- 14.5 mile ride.


----------



## wetpaint (Sep 7, 2009)

I have a Powertap on my MTB, however, I would probably get a Quarq if I did it over again. You can get a used Quarq off ebay for about $1000. The biggest thing for me is that with my Powertap, I know it's just a matter of time before it needs a $300 service. I have not had any issues with it so far, I've ridden in absolute downpours, mud without any loss of power data or the insides getting wet.

Trainers are not calibrated to be the same as the road, paying attention to time & power is all you need to pay attention to, not distance.


----------



## WR304 (Jul 9, 2004)

TritonBill said:


> I have power tap hub wheelset for my road bike but I don't have it on my 2012 Cannondale Flash 29'er. Would you suggest sticking with Powertap and just getting a back wheel and/or buying cranks with power built in for my Cannondale?!
> 
> I've been accumulating and training by power now since July. I use WKO+ 3 software and so far have found it very interesting. All my workouts are super specific and I have enjoyed it but this type of training program also makes it tough to ride with others when I am doing very specific workouts in varous training zones! WR304 and others... I may have to pick your brains now and then on the MTB side with power if I go there.
> 
> One things I've noticed on my PowerTap G3 hub is that the cadence it gives me seems to be pretty consistent as well as the mileage when I'm on a trainer. If anything it seems a little under represented when riding on the trainer. Often times I do what feels like a 1 hr ride and what feels like the equivalent of a 15.5 - 17 mph pace and it will calculate it as a 14- 14.5 mile ride.


I've got a Quarq Quattro but never got round to using it. The way I view it is that you should decide between a MTB Powertap or Quarq Quattro depending upon whether weight or gearing options are more important to you. Unless you're unlucky they both ought to be fairly reliable.

The MTB Powertap isn't currently available in the lighter G3 version. The Powertap Pro MTB hub with its bulky custom brake rotor adds quite a bit of weight onto the bike compared to a typical freehub and your choice of brake rotor. The Quarq Quattro in contrast isn't much heavier than the SRAM X0 chainset that it's based on.

Powertap Pro MTB hub including rotor. Claimed weight 680g
http://www.cycleops.com/en/products...page_images.tpl&product_id=618&category_id=20

DT 240s hub 240g & Shimano XT Icetech Rotor 115g. Claimed weight 355g
DT Swiss - 240s

The Quarq Quattro BB30 has a claimed weight of 723g, heavier than an aftermarket chainset but around the same as the SRAM X0 BB30 chainset that it's based on.
SRAM S2275 MTB Power Meter

SRAM X0 2×10 Official Photos and Specs - Bike Rumor

Although you'd think that makes the Quarq Quattro a clear winner it has one big issue. It uses the SRAM 120/80 BCD standard so the smallest inner chainring you can fit is a 26T. Used with 29" wheels that means you're potentially going to run out of gears if there are a lot of long steep climbs nearby. The Powertap Pro MTB hub lets you use any cassette and chainset so the gearing of your bike can be set appropriately when needed.

Mileage recorded on a turbo trainer doesn't mean much. (if you're trying to compare between MTB and road rides then the relative distances covered there don't mean much either) I'd concentrate on time and power output instead as they will be comparable between turbo sessions. If you're able to complete the session with a higher power output then it shows progress. Aiming to do a session of a set time duration on the turbo, rather than a set distance, would be the normal way to approach it.

Have a look at this thread too. It has some more discussion and various power files attached also.

http://forums.mtbr.com/xc-racing-training/mtb-power-meter-thread-696434.html#post7985055

I've been meaning to write a post about marking up an MTB power file from scratch for ages now but haven't managed to finish it yet. When I crashed four months ago (18 August 2012) it turns out that I actually dislocated my left clavicle and badly fractured my left femur (where it had been broken before previously). I haven't been able to ride at all since then. I've had an operation to have an external fixator put on the thigh in order to try and make the bones knit back together but it's likely to mean another six months off the bike still. There's no set date when it will be healed.


----------



## WR304 (Jul 9, 2004)

This youtube video is a webinar by Hunter Allen about using WKO+ 3.0. It has some interesting parts in. The video itself is quite long so I'd suggest downloading it with a program such as Freemake video downloader. You can then watch it back in short sections which are easier to digest. Watching a section of video, trying the feature in WKO+ 3.0 and then moving onto the next part of the video helps to make sense of it. 

The last question made me laugh. "What are the little triangles for in the quadrant analysis screen?"
Hunter Allen's answer: "We never worked out what they were for either." 






Learn the secrets to unlock your power meter data using TrainingPeaks WKO+ software by Hunter Allen - YouTube

Free Video Downloader | YouTube Downloader | FREE Download

.


----------



## wheel-addict (Aug 10, 2008)

WR304 said:


> Although you'd think that makes the Quarq Quattro a clear winner it has one big issue. It uses the SRAM 120/80 BCD standard so the smallest inner chainring you can fit is a 26T. Used with 29" wheels that means you're potentially going to run out of gears if there are a lot of long steep climbs nearby. The Powertap Pro MTB hub lets you use any cassette and chainset so the gearing of your bike can be set appropriately when needed.


I really appreciate the useful information in this thread. Can anybody comment on their experience with 26x38 gearing on a 29er in long endurance races with big climbs (50+ miles)? Do you find the 26 to be low enough (say for Leadville or Whiskey 50) or are a lot of competative people running more? For reference, I'm a fairly strong roadie (FTP ~300 and ~145 lbs), but I do like to keep a cadance of 90 or when climbing. Will I find myself slow-grinding/standing up a lot with 26-38 on a long hill climb?

I'm building up my first 29er HT after coming off a year of nothing but road racing. Before that I've only rode heavy 26ers for trail riding so I have no point-of-reference for 29er gearing. I'm trying to decide between the PowerTap and Quarq. This is a huge amount of money, so I'm concerned about the limitations of both.

WR304 had described the tradeoff very well above. WR304, you sound like a fairly strong rider, but also sound like you don't think 26T front chainring is low enough. This is making me nervous of choosing the Quarq, although it was my first choice due to lower weight and choice of rear hub vs PowerTap.


----------



## wheel-addict (Aug 10, 2008)

wetpaint said:


> You can get a used Quarq off ebay for about $1000.


I've been looking and looking on eBay, but no sign of any used MTB Quarqs. Am I looking for the wrong thing? There are many used road Quarqs for around $1000, used MTB Quarqs or MTB PowerTaps seem to be rare.


----------



## wetpaint (Sep 7, 2009)

You just have to save the search and watch them. There seems to be a few of them popping up a month. There is also one for sale on weightweenies for around ~$1200


----------



## WR304 (Jul 9, 2004)

I wrote that post a while ago. You also have a few new MTB power meter options being released at the beginning of 2013 to consider now: You have the Rotor power meter which costs about the same as a Quarq. The Rotor MTB power meter uses 104/64 BCD chainrings, has strain gauges in both cranks for measuring left/right power and you can use it with round or oval chainrings. It looks really interesting.






Rotor Power Meter Crank - YouTube

First look at new ROTOR Power Meter | DC Rainmaker

ROTOR PowerTechnical Specifications - ROTOR Power Cranksets

There's also the Stages power meter which fits into just the left hand crank, allowing you to use your choice of wheels and chainset. It's reasonably priced and only adds 20g of weight. There are plenty of MTB crank options available too. The accuracy of it appears to be being called into question however. Because the Stages power meter only measures the torque generated by your left leg it doubles the left legs power output as an estimate of power output from both legs. Have a look at the links below:

Stages Power

Stages Power Meter In-Depth Review | DC Rainmaker

StageONE Power Meter... I'm Stoked!

Choosing the appropriate gearing is one of those things where there's never a one size fits all answer. If you're a good climber then the 26 tooth inner ring is probably a non issue on 95% of climbs. If you never needed to use your granny ring on a 26" bike then a double chainset with 39/26 chainrings will be fine. Your w/kg is a lot higher than mine ever was last year so that's a big advantage straight away.

Using Sheldon Brown's gear calculator you can compare different gearing combinations. As a very rough estimate, if you had the same chainrings and sprockets fitted to a 26" wheeled bike as to a 29er you would need to use one sprocket lower on the 29er's rear cassette to be in the same gear as you would be on a 26" wheeled bike. The chart below is comparing 39/26 chainrings and a 11-36 cassette with 29" wheels to a triple chainring 44/32/22 11-32 cassette which was fairly standard a few years ago before double chainrings became popular.

Sheldon Brown's Bicycle Gear Calculator










Whether you'd get up a particular hill in a 26x36 bottom gear on a 29er really depends on the climb. There are some climbs which are ridiculous regardless of the gearing.

Vuelta a Espana 2012. Stage 16. Last km. - YouTube

The chart below is my best power outputs at different durations for 01 January 2012 to 18 August 2012. 18 August 2012 was when I crashed and broke my leg so that was it for 2012.










When you look at the same chart for 2011 it's clear from the power numbers that I had improved, especially over longer time periods which is what I was concentrating on. It's easy to get sucked into just looking at the 5 second, 1 minute, 5 minute and 20 minute durations in WKO+ 3.0 so having your own chart to keep track of the other time durations that may be more relevant is useful to have.










.


----------



## WR304 (Jul 9, 2004)

If you're going to be doing regular tests throughout the year then I think it's worth doing one at the start of the year too. That way you have an idea of what you can expect your trough to peak power outputs to be over the year.

If you look at this chart of my 20 minute FTP test results between 01 January 2011 and 18 August 2012 (when I crashed and broke my leg) you can see how the initial test in January 2011 wasn't great. After being ill over Christmas and doing very little cycling for the previous few months, due to bad weather, it took a while to build up my fitness levels again. After that rapid increase in the first part of the year the test results plateaued. Despite continuing to ride regularly I didn't make any major gains in 20 minute power output in the second half of 2011.

In January 2012 by contrast I'd kept riding and started the year at a higher fitness level. Both the initial test in January 2012 and my peak fitness in August 2012 were significantly better than the same dates in 2011.

I've also added monthly hours riding to the chart so you can see my power output plotted against that.










If you train for a certain duration then you're likely to find yourself improving at that duration but you have to be careful not to get too carried away with that, especially if power outputs below an hour aren't the main priority. Adding a report to show your longer duration power outputs can be helpful to stay focused.

Looking at the big picture like this I'm quite surprised by some of the trends. It's a good example of what you can expect if you follow the philosophy of "just ride lots". I didn't really have a set plan or set goals. The only real aim was to be fit enough to get round the road club runs without getting dropped. I got hammered mostly in that respect. There were a few rides where I did make it to the coffee stop still in contact with the group though, so it was partially successful.










For training I was doing more or less the same thing each year by starting off with hard rides in January, including some interval sessions and getting a good fitness improvement by March - April. In past years when I was racing I'd have been "racing myself fit" from that point on. As the weather improved I was losing interest in training for the sake of it and spending more time riding trails offroad instead. Enjoyable and good for bike handling but not very focused on fitness. In my power data my offroad rides always have a lower power output than road miles, which increases the amount of time spent in the lower power zones.

The (in)frequency of interval sessions is what I find surprising. I'd have thought that I would have done more than I actually did. I tend to have themes for each year. All I did outdoors was 6x4 minute intervals in 2011 These were 4 minutes on followed by 4 minutes off. In 2012 I only did 3x9 minute over-under intervals outdoors. Of the two types of intervals I think the 3x9 minute intervals worked better for what I was trying to do. Outdoors intervals were always part of longer rides. I'd usually do intervals in the first hour and then another 2-3 hours in the hills afterwards.










If you're using the Coggan power levels then 20 Minutes x 0.95 is supposed to be a rough estimate of your best 1 hour power. It seems to depend upon individual physiology how well it actually aligns though. 95% of my best 20 minute power is a lot higher than I can actually manage for an hour flat out. Along with the 20 minute tests I also did several 1 hour tests during 2011-2012 to see how they compared. You can see from the table above that my actual 1 hour power was a lot lower than the 20 minutes x 0.95 would suggest. The 1 hour power results were as good as I could do at the time. I definitely wasn't holding back.

There are other test protocols too. If you read any of the Chris Carmichael books then they use the CTS test instead. That will give you different power results to 20 min x 0.95 so the specific training zones aren't interchangeable. This PDF sets out that test procedure and explains what a under-over interval consists of.

https://www.trainright.com/assets/downloads/trainrightguidedescriptions2010.pdf

https://forums.mtbr.com/xc-racing-training/lthr-test-findings-need-help-760558.html

My favoured turbo training session (done when the weather was bad or my mountain bike was broken) consisted of this 1 hour interval session by Dr Andrew Coggan. It's a routine that I've done quite frequently in the past. I like it because it breaks the turbo training time into manageable chunks. The wattage figures are just his figures, you aim for your own zones (heart rate or power) at those durations. 30 second sprints are flat out.

_"Seriously, the best season I've had in recent years followed a winter
during which I did the following '90/90'90' workout 3 d/wk:

5 min w/u
20 min @ 275 W
5 min easy
5 min @ 325 W
2.5 min easy
5 min @ 325 W
2.5 min easy
0.5 min at 500 W
2 min easy
0.5 min at 500 W
2 min easy
0.5 min at 500 W
2 min easy
0.5 min at 500 W
2.5 min easy
5 min warm-down

The '90/90/90' refers to the fact that (almost by chance) the powers
used were about 90% of the best that I could produce for that duration
when at peak fitness. That made the session challenging enough that I
didn't lose too much fitness over the winter, but not so hard that I
ever dreaded the workout or burned out from doing it."_ *Andrew Coggan*


----------



## WR304 (Jul 9, 2004)

Taken from the big Slowtwitch thread on Powertap hubs. Some notes about MTB Powertap hubs: 

_"We do intend to make a 140mm rotor but first we need to build an MTB hub around the G3 platform. 
...
All PowerTap hubs are extremely water proof. For better or worse we have a history with this issue that has lead to some unique insight into overall robustness and durability of all our hubs. The G3 represents further refinement in this area and all our MTB hubs are now being built with G3 internals that offer this advancement. "_

*Jesse Bartholomew 
CycleOps Product Manager 
Follow me on Twitter @powertappro 
Saris Cycling Group*

Official PowerTap Thread (Page 6): Triathlon Forum: Slowtwitch Forums
.


----------



## wetpaint (Sep 7, 2009)

So does that mean I get G3 internals if I send my Powertap back? My ZO has risen to 540 from 512 last year. Power is still where it should be, but it's just a matter of time before I have to send it in for rebuild.


----------



## WR304 (Jul 9, 2004)

wetpaint said:


> So does that mean I get G3 internals if I send my Powertap back? My ZO has risen to 540 from 512 last year. Power is still where it should be, but it's just a matter of time before I have to send it in for rebuild.


I thought it was interesting that the updated internals were specifically mentioned in that thread. I'd guess that means new hubs will definitely be to the latest specifications. They really need to get on with releasing a full G3 MTB hub to match the road models also. That would save weight and counter one of the main criticisms of the current MTB Powertap hubs.

I'm not sure whether you're guaranteed the latest internals when being serviced. It's probably going to depend what the Powertap service centre has available as spares. If they've got old torque tube assemblies then those would be probably be used up first.

I'd have thought the best bet would be to contact Powertap and see what they say. In the UK you have to email and request they send you a servicing number for any work on a Powertap anyway.

https://powertap.paligapltd.co.uk/returnform.php

.


----------



## wetpaint (Sep 7, 2009)

Yeah, I'll probably give them call to see about sending mine in (USA). I have to try to get the timing in so I don't miss any race data. I'm not too concerned about the weight, even though the MTB version is pig. It'd be nice to have the separate electronics pod in case it goes bad again in the future.


----------



## wetpaint (Sep 7, 2009)

I just called and got an RA # to send my powertap back, Saris confirmed they're putting G3 internals in for rebuilds! That makes it much easier to stomach the $350 rebuild.


----------



## WR304 (Jul 9, 2004)

The good thing about a full Powertap rebuild with the torque tube being replaced is that you're literally getting a new hub back. All they keep is the hollow exterior hub shell that the spokes are laced to. The torque tube (which is everything inside the hub including hub bearings, axle etc) is unscrewed and a new assembly is screwed into the hub shell. 

I really ought to get my hub looked at too. It went haywire on 12 August 2012 after being caught in a ridiculous rain storm. I was out with the road club when the rain started. The club stopped to shelter under a rural petrol station's awning it was so bad. As the rain kept hammering down all these bikers came and stopped to shelter too, then several mods on scooters came and stopped too. As the rain continued lots of other cyclists were stopping too until eventually the forecourt was filled with all sorts of bicycles and motorbikes with everyone just looking out at the downpour. In the end we had to set off in the rain/ floods and then my Powertap started giving random power readings. 

After being dried out that night it appeared to be working ok again in the days afterwards. I crashed shortly afterwards 18 August 2012 though, so it hasn't been used since then. It would probably make sense to get the hub serviced whilst I can't ride.


----------



## TritonBill (Mar 12, 2010)

WR, you crashed in August and still can't ride?? I hope you get back out there this year!

Sent from my DROID BIONIC using Tapatalk 2


----------



## WR304 (Jul 9, 2004)

I'm normally quite good at crashing (lots of practice  ). The problem with this crash was that I was still attached to the bike so couldn't tuck and roll. I was trying to accelerate across a roundabout when my right foot came unclipped from the SPD pedal under full power. My right foot flew forwards and jammed between the front wheel and fork, breaking several spokes in the front wheel.










With the front wheel still completely locked by my foot the bike then flipped straight over at 16mph. From the damage spread evenly across the front of the handlebars, brake lever clamps and stem faceplate it looks like the front end was driven straight down into the tarmac.










I landed on my left shoulder, left hip and left thigh, dislocating my left clavicle and fracturing my left femur. I didn't slide at all, just a hard impact. Fortunately a passer by was able to pull my trapped foot out of the front wheel so that I could crawl out of the busy main road and lie down.

My left leg was a mess to begin with. It's had lots of previous operations and a major fasciotomy so there's barely anything left of the thigh besides scar tissue. My left leg is also paralysed from the knee down with poor circulation. When I re-broke the femur it wasn't a healthy bone, imagine a rotten branch, hollow on the inside with a MRSA bone infection just to make it more hassle. With a normal broken femur you can put a titanium pin inside for a quick repair. Because of the bone infection the hospital don't want to risk that as operating would make it flare up again.

The hospital have instead been trying to encourage new bone growth using an external fixator and the Ilizarov technique of pulling the two bone ends apart. This link explains how the Ilizarov technique encourages bone growth.

About Limb Lengthening

This is what is being tried with my broken left femur at the moment. There's some bone growth on the inside but the outside of the femur is still stubbornly refusing to grow back currently. That's why it's taking so long. There isn't a set time frame for these things.


----------



## WR304 (Jul 9, 2004)

Wheelbuilder.com have released a SRAM XX1 compatible freehub body for the Powertap hub now: 

http://www.wheelbuilder.com/powertap-mtb-xd-freehub-body-for-xx1-x01-compatibility.html


----------



## Henrik J (Apr 15, 2011)

I have the Wheelbuilder XX1 body on my new G3 hub. It seems to have some problems with the bearing as I am now on my third set of bearings on only 4 rides !!!. The inner bearing last from 1-2 rides and then it crashes. To me, it looks like wheelbuilder not have made a proper assembly as there is a little play between the “alu spacer” and the bearings. This result, that the bearings comes in tension when I tighten the wheel in the frame with the 12 mm thru bolt.
Do you or any other have any experience with the XX1 body from Wheelbuilder ??


----------



## WR304 (Jul 9, 2004)

Henrik J said:


> I have the Wheelbuilder XX1 body on my new G3 hub. It seems to have some problems with the bearing as I am now on my third set of bearings on only 4 rides !!!. The inner bearing last from 1-2 rides and then it crashes. To me, it looks like wheelbuilder not have made a proper assembly as there is a little play between the "alu spacer" and the bearings. This result, that the bearings comes in tension when I tighten the wheel in the frame with the 12 mm thru bolt.
> Do you or any other have any experience with the XX1 body from Wheelbuilder ??


I've got the Wheelbuilder 142x12mm axle but not the XX1 body. That's not very good if the bearing is only lasting one ride before failing. What have Wheelbuilder said about it?

Powertap have been dropping some heavy hints that they're going to be releasing an updated Powertap MTB hub with DT Swiss star ratchet internals, 142x12mm axle and XX1 freehub as original options:

_"The GS hubs will feature lots of DT Swiss hardware, including the axles, bearings, star ratchet, freehub body, end caps, and straight-pull flange. The front hub is essentially a stock 240s DT Swiss model.

*What DT Swiss hubs mean for mountain bikes and disc brakes*

PowerTap's move to DT Swiss hub internals will undoubtedly be a boon for durability and perceived quality, but the collaboration could also have big implications for the power meter company's stagnant mountain bike range, given the new engineering resources.

The biggest challenge to integrating a disc mount on any PowerTap hub has always been working around the large-diameter electronics cap, which, on the latest G3 and GS hub, houses the battery, wireless transmitter, and micro-USB port for updating the firmware. As a result, PowerTap's current mountain bike hub relies on a proprietary two-piece rotor and is limited to a 160mm diameter.

PowerTap product manager Jesse Bartholomew told BikeRadar that the company is already working on a new disc-compatible model based on the GS, with the same DT Swiss star ratchet internals, axle, and bearings.

This also means instant SRAM XX1 XD driver body compatibility and implies a wide range of axle fitments for both quick-release and thru-axle applications. Riders seeking a faster engagement speed would also have the option of installing DT Swiss 36-tooth ratchet rings.

Coupled with the already available 11-speed freehub bodies, this means PowerTap's upcoming new disc hub could find use on disc-equipped road and cyclocross bikes, as well as mountain bikes.

Bartholomew said he expects that the new hub will still rely on a proprietary rotor interface. However, the design isn't finalized, so we're still hoping for a disc-specific electronics cap and standard six-bolt rotor compatibility._

https://www.bikeradar.com/road/news/article/powertap-gs-bluetooth-power-meter--38163/









Powertap GS road hub showing the new DT Swiss star ratchet internals


----------



## Henrik J (Apr 15, 2011)

Sorry for my late answer. So far Wheelbuilder have been willing to send new body'es. On my last body I have punched the bearings some closer so the play is nearly like zero between the the bearing and the "tube" between. So far it has last after this little adjustment. But Wheelbuilder says that it's "normal" with the larger play but I my case I still think it was to big.


----------



## WR304 (Jul 9, 2004)

When I got my wheelbuilder.com 142x12mm thru axle it had play and wouldn't install properly. The freehub was binding as soon as you began tightening the skewer. I wrote a bit about it with pictures in Post #139 of this thread:

http://forums.mtbr.com/xc-racing-training/powertap-disc-405775-post8934129.html#post8934129

The problem wasn't with the Wheelbuilder thru axle. It was actually the Powertap hub itself that was out of spec. When I took the Powertap hub and had the torque tube replaced with a new one the Wheelbuilder axle installed correctly.

If you've been through multiple Wheelbuilder XX1 freehub bodies and they're all having major issues it could be that the problem is with your hub, rather than the freehub bodies?


----------



## Henrik J (Apr 15, 2011)

I do not think it is the hub itself. As the inner bearing of the body is pushed up to the axels "stop" edge the problem can only be in the body.
If I dismounted the axel and tighten it up in the frame incl. the body it would still have the pressure on the bearings if the play is to big as the frame will tighten from the end cap to the first bearing in the body, then to the "tube" and further on to the inner bearing of the body before it end up puching in the axels "stop" edge. Can you follow me ??


----------



## WR304 (Jul 9, 2004)

Posting a picture would come in handy to show where the problem is occurring.

Are you using the original Powertap axle, with that metal tube that acts as a spacer for the freehub, or are you using a Wheelbuilder 142x12mm axle where the spacer is machined into the axle?


----------



## WR304 (Jul 9, 2004)

I thought I'd post an update on the history and final demise of my Powertap hub.

It was purchased new October 2010 but not really used until January 2011 due to bad weather. It worked ok throughout 2011 until the start of 2012 where it's torque offset was way out of range. At that time it had a brand new torque tube (£425 GBP) fitted, new hub bearings and a Wheelbuilder 142x12mm thru axle installed to use with my new frame.

From February 2012 through to August 2012 it was ok. At the beginning of August 2012, a week or so before I crashed, I was caught in a massive rainstorm. The hub went haywire in the rain, reading 2,000 watts plus randomly before losing any power display at all (speed kept going from the hub though.) After a few days to dry out it was back to working normally again but the warning signs were there. 

I crashed and broke my leg soon after so the bike was then left packed away for a year whilst I couldn't ride. I started riding again outdoors 14 September 2013. After changing the batteries the hub worked but with a torque offset of 447 (out of correct range). I took it down to the UK service centre where it was recalibrated back to a torque offset of 512 and it had the hub bearings replaced (they were in a bad state).

In November 2013 I was caught in the rain for two hours. I was completely drenched and the hub died. When taken apart the battery cradle had shorted. After being dried out next to a radiator and with a new battery cradle installed it started working again, but only for a week before it stopped working suddenly whilst out riding in the dry. I wedged the battery cradle in place which got it working again for a couple of days before it stopped again on another dry ride, with no data from the hub. The issue apparently being the connection between the battery cradle and hub shaking loose. 

I securely fixed the battery cradle in place but after just 5 minutes riding the next day it stopped again, with no data again. The battery cradle connection definitely didn't shake loose this time so it's more than just a bad connection.

And that's where it's at. A hub that most likely needs another torque tube (£425 GBP). Money which I'm reluctant to spend on the old style hub. It still has the same weaknesses as my current Powertap hub so it would only be a matter of time until the new one went too.

If the Powertap GS MTB hubs with the DT internals were available now I'd get one of those but as they aren't I'm going to try a Power2Max crank based power meter for 2014.


----------



## WR304 (Jul 9, 2004)

Powertap have finally announced an updated MTB Powertap disc hub. It comes in a 142x12mm thru axle version and can be fitted with an XD driver to use with a SRAM XX1 cassette also.

_"The rear hub will be available in either 135mm QR or 142×12 thru-axle variants. Though it will require use of their proprietary 160mm brake rotor due to ensuring compatibility with their electronics. The unit will be available as 9/10/11 speed Shimano/SRAM, Campy or XD compatible. And finally as either 24 or 28 hole. The weight not including the rotor will range from 348g to 353g depending on the model.

From a product standpoint it's the same internals as a normal G3, just with a different shell. The final price isn't yet finalized - but will be less than $1,000US (how much less is up in the air)."_ *DCRainmaker*

http://www.dcrainmaker.com/2014/08/powertap-development-company.html

The spoke holes sound maybe like a typo as I'd assume it will come in a 32 hole version.


----------

