# Slack, Long, Low...vomit, arrrgh!!



## chelboed (Jul 29, 2005)

Why is "Low" such a "thing" now?








I love a tall stack height. I've got a 140mm head tube on my 26" Kinesis hardtail + 22mm of spacers, 50mm bar, and a 6degree stem.








I feel like I can manual, wheelie drop, steep-steep roll-ins, monster-truck across boulders, etc...much better and more comfy.

I don't understand how people can run such low stack heights (sub-600mm on an XL) and not have a radically taller saddle-to-handlebar height.

Thoughts?


----------



## Streetdoctor (Oct 14, 2011)

It's not 1990 anymore?


----------



## apriliano (Mar 21, 2007)

Because dropper posts?


----------



## alexbn921 (Mar 31, 2009)

Whats a 26er?


----------



## scottzg (Sep 27, 2006)

chelboed said:


> Why is "Low" such a "thing" now?
> I don't understand how people can run such low stack heights (sub-600mm on an XL) and not have a radically taller saddle-to-handlebar height.
> 
> Thoughts?


It's about increasing wheelbase while having the 'correct' seated and attacking weight distribution. The new bikes need a different riding style to work, so if you're riding a 2005 komodo it's not gonna gel right away.

I'm tall like you, and while i use a couple spacers and riser bars to get my hands in the right spot... i can put my hands almost anywhere reasonable and it's fine.


----------



## Legbacon (Jan 20, 2004)

Stack has nothing to do with low, slack, long. That refers to BB height, HTA, and Reach. Some brands have higher stack, and yet are LSL. Check Guerrilla Gravity | Denver, Colorado, USA Mountain Bike Manufacturing for example.

AND, I checked, it's 2017, you must be surprised.


----------



## mtg7aa (Jul 11, 2008)

Travis Bickle said:


> Stack has nothing to do with low, slack, long. That refers to BB height, HTA, and Reach. Some brands have higher stack, and yet are LSL. Check Guerrilla Gravity | Denver, Colorado, USA Mountain Bike Manufacturing for example.
> 
> AND, I checked, it's 2017, you must be surprised.


Yep. Low is referring to BB height, but at GG, we've found most folks prefer a taller stack height based on asking many folks to try different heights and tell us their thoughts.


----------



## alexbn921 (Mar 31, 2009)

I ride an XXL with my stem slammed and inverted. I can't buy a high stack bike.
The tallboy also has a flip chip and i've tried both low and high. Low is where it's at.


----------



## Walt (Jan 23, 2004)

Slack/long/low makes people feel safe on steep stuff and makes for a super stable predictable ride. If you're riding really tight twisty stuff (or just normal XC) there aren't really any advantages, and some considerable disadvantages, but if you want to charge gnarly (for you) stuff that sort of geometry is a great way to do it safely. 

For my own tastes, wheelbases and front centers got way too long in the last few years. The bikes take a ton of effort to steer and handle like pigs on my local stuff. Luckily, I can build whatever I want, so I just build myself *short* (wheelbase), slack, low.

Check out the latest issue of mountain flyer if you really want to geek out on "low"...

-Walt


----------



## Miker J (Nov 4, 2003)

Slack, long, and low...

Can't see that stupid add without thinking about your typical naked male nursing home resident.


----------



## scottzg (Sep 27, 2006)

mtg7aa said:


> Yep. Low is referring to BB height, but at GG, we've found most folks prefer a taller stack height based on asking many folks to try different heights and tell us their thoughts.


Why build a production frame with a taller head tube? Once it's tall enough that the front end is stable, can't the rider put the bars where they want with riser bars, stems, and spacers? Seems like you limit how low you can put the bars without any benefit.

Just curious to hear your thoughts.


----------



## Walt (Jan 23, 2004)

Super short head tubes + long travel forks = bad news. That, and 75mm of spacers looks goofy. 

It's really pretty easy to get your bars stupid low on almost any production bike unless you're very weirdly shaped or riding on a wheel size/fork that are just too big for you. Even then, a flat bar and a Syntace flatforce will get the bars WAY down there. 

-Walt


----------



## Cuyuna (May 14, 2017)

chelboed said:


> I don't understand how people can run such low stack heights (sub-600mm on an XL) and not have a radically taller saddle-to-handlebar height.
> 
> Thoughts?


I run 30mm stack height and a 40mm riser bar to get my hand grips at the point in space that suits my preferred riding position.


----------



## justwan naride (Oct 13, 2008)

@Cuyuna: I understand that most things in mtb are personal preference, but your setup contradicts everything I've learned playing around with spacers, stem lengths and different bars. Do you have enough traction on the front wheel going round flat corners? Have you tried a lower position? What kind of trails do you ride?

I'm 163 and the only way to ride a 29er comfortably and in control of the front wheel is with a flat bar and inverted stem. At least the ones I've ridden. 27.5+ is close in diameter so I imagine i'd have the same setup.


----------



## pvd (Jan 4, 2006)

I'm sure that the OP is happy riding slow. Most people want to ride fast.

It's not about long, slack, and low. That just what people who don't understand geometry say.

http://www.peterverdone.com/forward-geometry/


----------



## Cuyuna (May 14, 2017)

justwan naride said:


> @Cuyuna: I understand that most things in mtb are personal preference, but your setup contradicts everything I've learned playing around with spacers, stem lengths and different bars. Do you have enough traction on the front wheel going round flat corners? Have you tried a lower position? What kind of trails do you ride?
> 
> I'm 163 and the only way to ride a 29er comfortably and in control of the front wheel is with a flat bar and inverted stem. At least the ones I've ridden. 27.5+ is close in diameter so I imagine i'd have the same setup.


My setup above is the result of months of working with different stems, different bars, different seat positions. I've read a lot about cockpit setups too and I understand the dogma of "long/low/slack", but I've found that as a total mountain biking experience on this particular bike, my handlebar/riser combo is what maximizes that experience for me. I don't have any trouble controlling the front wheel, and I never get washouts even on the loose shale, nor on the extensively leaf-covered trails that we see in the fall, as I found out yesterday.

I ride 95% singletrack on rocky shale and iron ore overburden, moderate amount of rocks and roots. Some trails are softer, mostly sand/clay.

I'm pretty sure that the disconnect is that you and I have different expectations for our riding experience, therefore our bikes are set up differently to reflect how each defines a "good ride" and fun on the trail.

The difference between the OP and me is not that I can't understand the "long/slack/low" dogma...I do.... it's that I don't care how other people like to set up their bikes - it doesn't have anything to do with me. They're working with a different geometry, different physique, different expectations. Going fast isn't my primary goal. I set up my bike to maximize what I want to get out of mountain biking. So far, it's working great. If and when my expectations change, well...there's no shortage of stems and bars out there. In fact, there's no shortage of stems and bars on the shelf in my workshop.


----------



## incubus (Jan 20, 2004)

Cuyuna said:


> My setup above is the result of months of working with different stems, different bars, different seat positions. I've read a lot about cockpit setups too and I understand the dogma of "long/low/slack", but I've found that as a total mountain biking experience on this particular bike, my handlebar/riser combo is what maximizes that experience for me. I don't have any trouble controlling the front wheel, and I never get washouts even on the loose shale, nor on the extensively leaf-covered trails that we see in the fall, as I found out yesterday.
> 
> I ride 95% singletrack on rocky shale and iron ore overburden, moderate amount of rocks and roots. Some trails are softer, mostly sand/clay.
> 
> ...


Very well said.

For me personally, I like long (long reach that is) because of my positive ape index. Slack HTAs is something that I personally can adapt to. But too low a BB is a deal breaker for me. Not because of how the bike feels, but because of the pedal strikes compromise I'd have to make.

There is no one bike/setup that is perfect for everybody everywhere.

Sent from my iPhone using Tapatalk


----------



## chelboed (Jul 29, 2005)

http://www.peterverdone.com/forward-geometry/
Thanks for the link, I'll check it out.


----------



## dbhammercycle (Nov 15, 2011)

Walt said:


> Slack/long/low makes people feel safe on steep stuff and makes for a super stable predictable ride. If you're riding really tight twisty stuff (or just normal XC) there aren't really any advantages, and some considerable disadvantages, but if you want to charge gnarly (for you) stuff that sort of geometry is a great way to do it safely.
> 
> For my own tastes, wheelbases and front centers got way too long in the last few years. The bikes take a ton of effort to steer and handle like pigs on my local stuff. Luckily, I can build whatever I want, so I just build myself *short* (wheelbase), slack, low.
> 
> ...


Pic of said *short*, slack and low?

I also don't like the long of my fatbike, newest bike, in the tighter and twisty spots, so I still ride my RMB Blizzard (that's 26 skinny) for those spots or my 10yr old SS for the summer. That said, the longer wheelbase on the fatty is better for me in the snow. I'd like to see what you mean by *short*, slack and low...

Also, wheel/tire influence on geo, bigger wheel and tire combos seem to go hand in hand with slack, long and low, no?


----------



## Fix the Spade (Aug 4, 2008)

scottzg said:


> Why build a production frame with a taller head tube? Once it's tall enough that the front end is stable, can't the rider put the bars where they want with riser bars, stems, and spacers? Seems like you limit how low you can put the bars without any benefit.


Short headtubes result in the load from the fork/bars being spread over a smaller area, both within the head tube and at the welds between head/top/down tube.

Not a problem for many riders, but 210lbs of XL man and a 200mm brake rotor on there and you have a recipe for damage. Cracks forming behind the headtube at the butts/welds of the top/down tube are not uncommon, or ovalised head tubes. Besides for a tall rider even a 150mm head tube will still end up with 30-50mm of spacers under the stem, it always does for me even on 29ers.


----------



## mtg7aa (Jul 11, 2008)

scottzg said:


> Why build a production frame with a taller head tube? Once it's tall enough that the front end is stable, can't the rider put the bars where they want with riser bars, stems, and spacers? Seems like you limit how low you can put the bars without any benefit.
> 
> Just curious to hear your thoughts.


The head tube heights we use were based on polling a large sample of riders on handlebar height, and getting a number of people to try different heights and tell us their preferences. Then, the head tube heights were set such that the people that preferred the lowest setup for a given frame size run no spacers under the stem, and the people that prefer taller setups do not need to run a 50mm tall stack of spacers.

The validation is in the setups: >95% of riders run a setup on the current generation GG bikes with 0-30mm of stem spacers. And those that are statistical outliers have the option of custom frame geometry. Periodically we build a size medium frame with the head tube from a size large or small, for example.


----------



## Walt (Jan 23, 2004)

*Short, slack, low!*

Here you go. I'm building this one for myself right now (mostly because I can't fit a plus tire on my old buddy Stupidmobile)

Note that this bike is built for 165mm cranks. I would go shorter but the options get pretty crappy below that length.









-Walt


----------



## chelboed (Jul 29, 2005)

Why such short crankset?


----------



## chelboed (Jul 29, 2005)

Holy crap!! That is a low BB! Do you ride rock or chunk, or is it a gravel rig or something?


----------



## Feldybikes (Feb 17, 2004)

Just a note to anyone looking at Walt's geometry for inspiration: he's built like a T-Rex, so YMMV. 

(And it just occurs to me now, Walt, with our near-identical heights, but my +6" ape index, I wonder if i somehow cosmically got your missing arm length???)


----------



## chelboed (Jul 29, 2005)

pvd said:


> I'm sure that the OP is happy riding slow. Most people want to ride fast.
> 
> It's not about long, slack, and low. That just what people who don't understand geometry say.
> 
> http://www.peterverdone.com/forward-geometry/


I could nerd-out on that stuff all day. Good read.


----------



## Walt (Jan 23, 2004)

I like low BBs, much quicker to turn in and more stable on the rough fast stuff too. 

Of course, they suck if you hit your pedals on stuff constantly. So I just use short cranks (in this case 165s, which are the shortest decent ones I can get - I'd go even lower if there were a good 150mm option). It also helps that the local terrain is not super rocky in general. 

Why such short cranks? Because for most riders (including me) ideal power output is actually around 140-150mm. Yes, really (albeit only by a tiny amount). You can read all about it in this month's issue of Mountain Flyer (I built the test rig), and you can also go google the University of Utah study (I was not involved in that one) if you want to geek out a bit more. 

Everyone is on cranks that are too long, basically, especially for mountain bikes. And the upsides of using shorter ones are HUGE in the era of dropper posts (if you run 150mm cranks, you have to raise your saddle about 25mm to get proper leg extension - which means on descents you have a LOT of saddle height to contend with on a rigid post). 

Next big thing. You heard it here first! 

-Walt


----------



## Feldybikes (Feb 17, 2004)

chelboed said:


> I love a tall stack height. I've got a 140mm head tube on my 26" Kinesis hardtail + 22mm of spacers, 50mm bar, and a 6degree stem.


To the OP: with that being a 26" bike, subtract 25mm off the bar height, 40mm off the head tube and 10mm off the spacers and you're sitting at a relatively normal-proportioned stack height for a 29er, even considering your bike's lack of BB drop.


----------



## pvd (Jan 4, 2006)

Walt,

These cranks go to 155mm and are excellent. I belive they have other sizes not listed.

AM / DH CRANKS | Canfield Brothers Bikes | Cranks for Downhill


----------



## Walt (Jan 23, 2004)

Pete, I LOVE YOU!!!!

Time to add some more BB drop...

-Walt


----------



## pvd (Jan 4, 2006)

I've used them on girlfriend bikes and on my flow racer (280mm BB sagged).

https://www.peterverdone.com/flowmaster-2-the-z-74-mark-ii/


----------



## Walt (Jan 23, 2004)

Feldybikes said:


> Just a note to anyone looking at Walt's geometry for inspiration: he's built like a T-Rex, so YMMV.
> 
> (And it just occurs to me now, Walt, with our near-identical heights, but my +6" ape index, I wonder if i somehow cosmically got your missing arm length???)


Ha! Yes, that's possible.

Seriously, don't go copying this, anyone. This is *specific to me*. It will probably fit 99.9% of the general population horribly.

But look into short cranks. Really.

-Walt


----------



## Eric Malcolm (Dec 18, 2011)

Cuyuna said:


> My setup above is the result of months of working with different stems, different bars, different seat positions. I've read a lot about cockpit setups too and I understand the dogma of "long/low/slack", but I've found that as a total mountain biking experience on this particular bike, my handlebar/riser combo is what maximizes that experience for me. I don't have any trouble controlling the front wheel, and I never get washouts even on the loose shale, nor on the extensively leaf-covered trails that we see in the fall, as I found out yesterday.
> 
> I ride 95% singletrack on rocky shale and iron ore overburden, moderate amount of rocks and roots. Some trails are softer, mostly sand/clay.
> 
> ...


I'm going to print this out and put it on my wall......

Eric


----------



## vernondozier (Aug 31, 2011)

Cuyuna said:


> My setup above is the result of months of working with different stems, different bars, different seat positions. I've read a lot about cockpit setups too and I understand the dogma of "long/low/slack", but I've found that as a total mountain biking experience on this particular bike, my handlebar/riser combo is what maximizes that experience for me. I don't have any trouble controlling the front wheel, and I never get washouts even on the loose shale, nor on the extensively leaf-covered trails that we see in the fall, as I found out yesterday.
> 
> I ride 95% singletrack on rocky shale and iron ore overburden, moderate amount of rocks and roots. Some trails are softer, mostly sand/clay.
> 
> ...


This above is my sentiment exactly. Took me a year to get it right. Cockpit position is so nuanced for me.....After a couple years of learning new geo and bikes, it boils down this: whatever frame I get, must have sizable HTube. If I am off even a half inch too low, I am miserable. I can fly downhill, do singletrack, hairpins, all day trips with what riders consider "high" cockpit. When I do my rides, I maybe go up hill for couple miles, mile of level singletrack, then 1 mile very downhill and 2 miles moderate with twists. This is sort of my norm. So basically, decent headtube lengths and forks with most of their steer tube left are a must when switching out rigs. I got extremely lucky frankly when I bought the On one codeine from planet x a couple years ago. I wanted full suspension, but for a deal, picked new one up for $500+/- and the head tube is sizable compared to most other newer frames. Fits like a glove, even with the used forks which had a little steer tube cut. Riser Spank bars and a tiny bit of rise in thomsen stem make this feel like it was made for me. I have been on evil, transition, and scott, to test, but would have had to go through the whole cockpit fit debacle again. Maybe if I did super techie boulder drops I would need something else, but I want to want to be riding, comfort is a must.


----------



## vernondozier (Aug 31, 2011)

Re shorter cranks, I was stumped with my norco torrent, trail geo type hard tail, had dropper post, long story short, removed 175mm tried some old 165mm and voila, normal again...6'1" on xl, my logic was that the dropper minimum was too long and so bottom of pedal stroke to deep, I ditched the dropper anyway, kept the 165mm and can ride all day now. Flat or up/down. Nothing scientific for me, just felt right in the up and down positions on the pedal stroke.


----------



## Ryder1 (Oct 12, 2006)

vernondozier said:


> removed 175mm tried some old 165mm and voila, normal again...6'1" on xl, my logic was that the dropper minimum was too long and so bottom of pedal stroke to deep, I ditched the dropper anyway, kept the 165mm and can ride all day now. Flat or up/down. Nothing scientific for me, just felt right in the up and down positions on the pedal stroke.


The 165mm cranks fixed your problem when running a dropper, but now that you've ditched the dropper, why not go back to 175? Have you tried this combo yet?


----------



## BigHit-Maniac (Apr 13, 2004)

Because there's a difference of feeling like you're riding "in" the bike or you're an appendage on "top" of the bike. 

Trial rode a Cannondale Jeckyll (2015ish). It felt like I was sitting waaaaay "on top of it"

Test rode a Trek Remedy & Slash... and I felt more "in" the bike and waaaay more comfortable. 

It's all personal preference really. 

But like the car industry trying to literally shove Crossover SUV's down our throats, the bike industry is cramming this sh** down our throats. 

Ride what makes ya' feel comfy man!


----------



## justwan naride (Oct 13, 2008)

Cuyuna said:


> My setup above is the result of months of working with different stems, different bars, different seat positions. I've read a lot about cockpit setups too..
> 
> ...there's no shortage of stems and bars out there. In fact, there's no shortage of stems and bars on the shelf in my workshop.


Thanks for taking the time to reply. I still can't get my head around it, but it seems like you did plenty of testing and found what works for you. I'm just curious on everything about bike setup and if met you at the trailhead I'd definitely ask to get your bike for a ride.

Personaly I'm a huge fan of long/low/slack, although I still ride my short/low/steep bike as well. Both are fun, but for me the newer style of geo has a much broader range of trails, conditions and speeds where it feels good. I've always felt my old bike was unbalanced, like the rear center was longer and the front shorter than ideal. I had to compensate with lots of body english with little room for error.


----------



## alexbn921 (Mar 31, 2009)

There is something magical about having your stem length match your fork offset. All of your steering movement pivot around the center of the front hub. The control and feedback are amazing.
I will never buy another bike that requires a stem that is significantly different from my forks offset because of this. BB and HTA are more trail dependent, although as low as possible without rock sties seems best.


----------



## WHALENARD (Feb 21, 2010)

I wish I could get along with shorter cranks...I can't. I've given 170's and 165's a shot for an entire season and notice a huge difference in power and efficiency every time I hopped back on 175's. Don't care much about rock strikes but the extra control from closer foot offset was great. As a guy who's been riding 175's for ever is this just conditioning or what? Does crank length effect anti squat in really torquey pedaling...think granny gear & steep?


----------



## Walt (Jan 23, 2004)

Crank length has zero effect on the suspension kinematics of the bike - that's determined by chainring/chainline and pivot placement(s). Foot speed constraints will often mean people run smaller chainrings with shorter cranks, though - which would for basically all suspension bikes decrease squat/bob. It could theoretically mean weird pedal feedback if you went nuts and used a super tiny ring, and had a bike with a ton of antisquat, though I'd be surprised if you could really find that theoretical case IRL.

Did you actually go do an LT test or something along those lines with the shorter cranks? Everyone is different and you might very well be better off on long cranks, but the evidence is basically that *crank length doesn't matter much* for power output for most riders. Any difference you felt was *probably* in your head. 

-Walt


----------



## Walt (Jan 23, 2004)

alexbn921 said:


> There is something magical about having your stem length match your fork offset. All of your steering movement pivot around the center of the front hub. The control and feedback are amazing.
> I will never buy another bike that requires a stem that is significantly different from my forks offset because of this. BB and HTA are more trail dependent, although as low as possible without rock sties seems best.


Not to further derail, but the difference in what your hands do between even the shortest and longest commonly used stems is negligible. You probably like the front center/trail on your bikes with ~50mm stems. The stem length itself is irrelevant.

That said, if you're buying a bike and you want a certain feel, stem length (as needed for the reach you want) *can* be a proxy for front center (assuming you're comparing bikes with similar HTA/STA/etc). So it's not a terrible way to roughly determine if you'll like something.

-Walt


----------



## alexbn921 (Mar 31, 2009)

I will ride the mountain on our group ride with a 50mm stem on my tallboy and swing by the house to pick up my 170mm stem Super V for the pub crawl afterwards. It's such a shock to switch bikes. Takes my brain a couple of corners to get used to the tiller.
I tried a 60mm stem on my tallboy and while I liked the extra reach, I could feel the difference in handling. I also have tried bar width from 720 to 810. The bigger bars fit me much better even though I always thought they would suck. My last bike had 680 bars and I thought 760 would be pushing my limit.
I order a 44mm offset crown as my front center is to long relative to the back end. Short stays are not so great on an XXL bike.
FYI I rode a Mojo 3 XL with a 90mm stem and it felt totally wonky. Liked the bike overall, but it was 45mm to short.


----------



## WHALENARD (Feb 21, 2010)

I realize crank length is not a factor in suspension kinematics directly but wonder if power delivery in steep torquey climbing does not effect anti squat in relation to crank length. I'm by no means an expert on the subject and am more or less just spit balling to have a better understanding of why short cranks feel so awkward to me. Anecdotally my stumpjumper evo seemed to squat more under torquey climbing with 165 vs 170 vs 175 cranks. All things being equal, back to back , same day, same trail. Perhaps I was feeling the leverage difference, ldk, but it certainly seemed to squat more and was noticeable. My conclusion at the time was my power delivery overwhelming the low speed compression on the shock. I've found horst of yesteryear really takes a smooth constant chain tension to not squat under hard efforts. 

I've read the University of Utah study a ways back along with everything else I could find on the subject, but that just didn't seem to translate in my trials with them. It seems logical that inseam would play a roll as would the simple fact of length=leverage. I also can't get along with newer oval rings while everybody seems to love them so I'm certainly an outlier.


----------



## Walt (Jan 23, 2004)

alexbn921 said:


> I will ride the mountain on our group ride with a 50mm stem on my tallboy and swing by the house to pick up my 170mm stem Super V for the pub crawl afterwards. It's such a shock to switch bikes. Takes my brain a couple of corners to get used to the tiller.
> I tried a 60mm stem on my tallboy and while I liked the extra reach, I could feel the difference in handling. I also have tried bar width from 720 to 810. The bigger bars fit me much better even though I always thought they would suck. My last bike had 680 bars and I thought 760 would be pushing my limit.
> I order a 44mm offset crown as my front center is to long relative to the back end. Short stays are not so great on an XXL bike.
> FYI I rode a Mojo 3 XL with a 90mm stem and it felt totally wonky. Liked the bike overall, but it was 45mm to short.


Yes, in those cases you are feeling the different weight distribution between the wheels, not the length of the stem in itself. Swapping stems on an existing bike causes dramatic changes in weight distribution, and of course riding your old Cannondale (with probably 4" less front center!) will feel wonky.

You really don't steer with the bars anyway, but like I said, stem length is an ok proxy for front center for most people most of the time. Since this is a framebuilding forum, though, I have to be picky about it and steer the framebuilding folks away from the idea of designing a bike around a stem length.

-Walt


----------



## Walt (Jan 23, 2004)

WHALENARD said:


> Anecdotally my stumpjumper evo seemed to squat more under torquey climbing with 165 vs 170 vs 175 cranks. All things being equal, back to back , same day, same trail. Perhaps I was feeling the leverage difference, ldk, but it certainly seemed to squat more and was noticeable. My conclusion at the time was my power delivery overwhelming the low speed compression on the shock. I've found horst of yesteryear really takes a smooth constant chain tension to not squat under hard efforts.


If anything, it should be the opposite, since for the same foot speed, you'll be doing more RPM on the shorter cranks - and riding a slightly lower gear (for the same overall ground speed). Unless you are really unusual, higher cadence should mean a smoother overall stroke.

That said, the whole point of all these studies is that crank length can be chosen based on basically whatever the hell attributes you want (in my case, lowest possible COG) and you probably won't pay a significant price in efficiency or power regardless.

-Walt


----------



## alexbn921 (Mar 31, 2009)

Walt said:


> Yes, in those cases you are feeling the different weight distribution between the wheels, not the length of the stem in itself. Swapping stems on an existing bike causes dramatic changes in weight distribution, and of course riding your old Cannondale (with probably 4" less front center!) will feel wonky.
> 
> You really don't steer with the bars anyway, but like I said, stem length is an ok proxy for front center for most people most of the time. Since this is a framebuilding forum, though, I have to be picky about it and steer the framebuilding folks away from the idea of designing a bike around a stem length.
> 
> -Walt


I picked a front center that would accommodate the stem length that I wanted for my desired fit. I agree that you not steer the bike with the bars, but it is nice to have the center of your contact patch pivot with your bars.
Since we are taking about building a frame, what would be your perfect stem length for a trail bike. Also what offset do you think is best for a 29er wheel? Most manufactures seem to play it safe and give 29ers less trail than equivalent 27.5 bike.
I'm an outlier at 6'4" with a long reach. I find that reach + stem = 560mm feels right. Not a lot of frames will let me run a short stem. The ones that do have the same rear end as the small bikes with 100mm smaller front centers. It messes with the weight distribution to have such a huge swing on one side of the BB.
All kinds of ways to correct for this imbalance, but most of them are compromise setups.


----------



## Walt (Jan 23, 2004)

There is no perfect stem length for a trail bike, or any other bike. Hell, there's no perfect front center! Everyone likes something a little different (and rides different terrain), so you just have to play around until you find it. 

If you are asking *me personally* what I like, I tend to like around 680mm front center for XC and 20-30mm more for "trail" (ie, for falling off things) riding. Of course, I tend to run more steering trail on the "trail" bike, which is accomplished here with head tube angle, which adds front center... so I actually run pretty similar stem lengths for XC and trail riding, though the weight distribution is quite different. 

I don't use reach numbers because they vary too much with stack height and hence are pretty useless - I just use front center for all front-end-length decisions. 

Don't get me started on the identical chainstay lengths on XS-XXL bikes. You are preaching to the choir. Lots of smaller folks out there are on stays that are way too long, many tall folks are stuck with too short. The reality is that manufacturing different rear ends for every frame would get prohibitively expensive, though, so you're not going to see it from mass produced bikes (with rare exceptions) anytime soon. 

-Walt


----------



## alexbn921 (Mar 31, 2009)

My bike has the seat and handlebar setup the way I like it but the front center is to long in comparison to the rear center. For me to get an XL/XXL bike with the correct ratio, I need a longer stem and usually push my seat back slightly to compensate.
I'm reducing the front center by 7mm with a shorter offset to get more weight on the front wheel and increase trail. I ride stupid steep trails at high speed so this should tune the bike to my style.


----------



## Ryder1 (Oct 12, 2006)

Interesting thread.



WHALENARD said:


> Anecdotally my stumpjumper evo seemed to squat more under torquey climbing with 165 vs 170 vs 175 cranks. All things being equal, back to back , same day, same trail.


Did you lower/raise your saddle as you rode various cranks? Either way, you've got another variable creeping into your comparison.

If you raised your post for 165 cranks without moving the saddle forward, you've lengthened your reach to the grips, possibly compromising some core stability. Plus

higher & more rearward saddle = more weight on rear wheel = more squat when climbing

If I extend my post just a wee bit, I can feel a difference in rear suspension performance when climbing seated, for the worse. I don't mind running a little lower than "normal" for this reason. My bb-to-saddle is 820+mm (I've got Walt proportions) so I'm already sitting above the rear axle on climbs - not keen on making things worse. Well-distributed weight = predicable & efficient climbing IME. I find the same phenomenon if I push my cleats (from full rearward) a bit forward: Post must go up, seated weight shifts back, and F/R balance suffers.


----------



## WHALENARD (Feb 21, 2010)

Ryder1 said:


> Interesting thread.
> 
> Did you lower/raise your saddle as you rode various cranks? Either way, you've got another variable creeping into your comparison.
> 
> ...


I think that's a fair point & seat tube angle would certainly be a factor here. On my following I can definitely feel a difference in 10ish mm seat height. However, on steep stuff leaning forward and scooting forward for 5mm is pretty negligible. I felt a difference with the cranks basically everywhere including standing. I gave the 170's a good long run to adapt but they just never jived. I'm tempted to try them again on a new build hence me butting in here.


----------



## pvd (Jan 4, 2006)

alexbn921 said:


> I'm reducing the front center by 7mm with a shorter offset to get more weight on the front wheel and increase trail. I ride stupid steep trails at high speed so this should tune the bike to my style.


Stop. Reading. Ad. Copy. And. Magazines.

http://www.peterverdone.com/high-trail-mtb/


----------



## alexbn921 (Mar 31, 2009)

pvd said:


> Stop. Reading. Ad. Copy. And. Magazines.
> 
> http://www.peterverdone.com/high-trail-mtb/


Great article but you didn't seem to have any conclusions other than you liked a certain amount of trail. I've always been on bikes that were too short and overloaded the front wheel. Now I have a bike that's cockpit fits me but the front center is to long. I can't change the rear to balance it so i'm decreasing the front center. Will this make the bike better or worse? I'll have the new uppers in a couple weeks and find out. I like to tinker and am constantly trying new setups to fine tune the feel of the bike. Some are good and some are not. I have no problem admitting that it didn't work if it's bad.
Anyway I'm looking for balance. Pretty sure you have to try out different setups to find the best one for you.


----------



## pvd (Jan 4, 2006)

I find it hard to believe that you are on a bike that will be better balanced by moving the front wheel rearward. Either your body position is horrible or you are associating feel incorrectly.


----------



## alexbn921 (Mar 31, 2009)

My front center is 802mm and the rear is 432mm. Both at extremes for 29er short travel trail bike.


----------



## pvd (Jan 4, 2006)

I'm 5'10" and a 32" inseam. Totally average. My bike works very well with an 820mm front center.


----------



## Walt (Jan 23, 2004)

I would say it's worth a try (lower offset fork, that is). 

The thing is, bikes are like surfboards - there are LOTS of configurations that can be fun on lots of different trails for different riders. You don't have to be optimizing for "pure speed", you can optimize for the *feeling* that puts a smile on your face, or the configuration that lets you finally clean that rock garden (even if it makes you a little slower everywhere else), or anything else that makes you smile when you ride. 

There are guys who ride pretty big waves on skimboards, just because they think it's fun. It's harder and more dangerous and arguably just stupid from a performance standpoint - but they enjoy it, and that's all that matters, right? 99% of mountain bikers don't race, so racing objectives shouldn't usually be the end goal.

Shorter front center and more steering trail might feel totally awesome to Alex (a lot of my own bikes have less front center and more trail than "normal"). Or it might not. But there's nothing to lose by trying it out.

-Walt


----------



## richwolf (Dec 8, 2004)

I got caught up in this short crank thing many years back. My brother tapped some cranks to be around 145 MM or so if I remember correctly. Gave them a good shot but it was totally weird. I am 5'5" so I thought shorter cranks would be the way to go. 
Now I run either 170's or 175's and am completely happy with them.
A friend of mine who is a huge experimenter and quite a good cyclist (roadie) tried power cranks which are independent cranks and he also tried crank lengths from around 140 and up. He gave up on both after lots of experimentation.

Here is a link to power cranks: https://www.powercranks.com/


----------



## phidauex (Apr 17, 2013)

Love this discussion.

Howard Zinn has been espousing shorter cranks for years, and Lee McCormick of "Mastering Mountain Bike Skills" is now on board. There don't seem to be any disadvantages of a shorter crankset, but tons of disadvantages of longer ones.

One important note is that your gain ratio does go down a bit, so you compensate with a slightly different gear ratio. Track riders have known this for decades, running 160-165mm cranks with compensated singlespeed drives.

I don't know where the "optimal" is, but I'm now convinced that most people riding stock 175mm cranksets are riding something way too long. Whether 170, 165 or something crazy like 150 are optimal I couldn't say.

At the end of the day, as long as we know what we are optimizing too, we'll be on the right track. I've ridden 20+ miles on a child's tricycle and had a great time (super short cranks, too). Always pleased to see continued innovation and change.


----------



## Ryder1 (Oct 12, 2006)

phidauex said:


> Howard Zinn has been espousing shorter cranks for years


I believe Zinn recommends cranks proportionate to leg length. His website recommends 195mm cranks for me (925mm x .21).

I recognize the benefit of being able to run a lower BB, but I've owned a road bike with 172.5 (hated it) and won't run anything less than 180 on a SS. Maybe a larger manufacturer like Trek can design smaller sizes with shorter stays, lower BB, and shorter cranks, and still be cost efficient. Two designs?


----------



## MikeDee (Nov 17, 2004)

phidauex said:


> Love this discussion.
> 
> Howard Zinn has been espousing shorter cranks for years, and Lee McCormick of "Mastering Mountain Bike Skills" is now on board. There don't seem to be any disadvantages of a shorter crankset, but tons of disadvantages of longer ones.
> 
> ...


Shorter cranks mean lower torque. You need lower gears to compensate for going shorter. For 29ers, low enough gears are already a problem, especially where I ride and at my age.


----------



## briderdt (Dec 14, 2012)

phidauex said:


> ...Track riders have known this for decades, running 160-165mm cranks with compensated singlespeed drives.


Track bikes use the shorter cranks to avoid pedal strikes on steep banking, and not have to elevate the BB so much to affect the overall stability of the bike.


----------



## Ryder1 (Oct 12, 2006)

Re: power

Every time I've delved into the research, the takeaways seemed to be that shorter cranks may have value at high RPMs or for short-legged riders, and that preference/performance varies considerably among subjects.

If you have data on the one rider that matters (yourself), the average of a group of other riders isn't much help. But, if you don't have that data, and are wondering whether to make a financial investment, then the studies may be of use.


----------



## incubus (Jan 20, 2004)

Norco is one manufacturer that uses different sized rear triangles depending on frame size. 

The commonly held notion that chainstays need to be as short as possible seems silly. 

I thought that the old rule of thumb was that a plumb line from the center of the seatpost clamp should fall halfway between the chainstays. That said, modern bikes with steep STAs likely nullify this rule


Sent from my iPhone using Tapatalk


----------



## dr.welby (Jan 6, 2004)

Back in my singlespeed days I tried 170s for a year instead of 180s. I dropped the chainring size by the same percentage to keep the gearing the same. It never felt as fast on the climbs so I eventually went back to 180s.

The physics should work out the same - you're trading off more pedal rotations for a shorter power stroke, but I think that there's a physiological difference from the work done by your upper body and core when switching from one leg to the other. It seemed like the isometric work didn't quite get the savings of the shorter power stroke. This is on low-rpm, out of the saddle efforts.

Spinning on the flats they felt great though. Now that I'm old I don't ride singelspeeds anymore and just have 175s on everything, mostly due to their ubiquity.


----------

