# Alfine belt-drive watch-outs and design considerations?



## Meriwether (Jul 26, 2007)

I'm building a Alfine 8 commuter/touring rig with a Gates Centertrack belt. I've read all the Gates has to offer and it's a great resource of PDF's.

The frame will use a traditional 68mm threaded shell, 130BCD cranks, use either PMW Rockers or Sliders, and need to fit 40mm tires, full fenders, and racks. The only option for the Alfine is a 24t cog, and he wants to use a 46t up front. 

I know i'll need to put a big dimple in the outside of the driveside chainstay to get the right belt-line and for the ring to fit. I know there's certain belt lengths that dictate the chainstay length I can use, but there are 3 options to choose from with this cog/ring combo. They recommend a minimum of 12mm of adjustment in the dropout or eccentric BB so that's no problem with Rockers or Sliders. 

Does anyone have recommendations on:

- chainstay length and belt-drives?

- chainstay type/brand/wall thickness, 

- dropout choice, 

- crank selection for maximizing lateral adjustment in chainline, 

- any other 'watch-outs' that I should keep in mind while designing and building since it's my first belt and Alfine frame.

I'd prefer to use Rockers since the brake is out of the way of the fenders and rack eyelets but the lack of tensioning screws is a bummer for a belt-drive. Do any of you have experience with this?

Thanks for any advice,
Whit


----------



## G-reg (Jan 12, 2004)

Meriwether said:


> I'm building a Alfine 8 commuter/touring rig with a Gates Centertrack belt. I've read all the Gates has to offer and it's a great resource of PDF's.
> 
> The frame will use a traditional 68mm threaded shell, 130BCD cranks, use either PMW Rockers or Sliders, and need to fit 40mm tires, full fenders, and racks. The only option for the Alfine is a 24t cog, and he wants to use a 46t up front.
> 
> ...


I'd give thought to using a 73mm shell and a 104mm crank. The downside to that is you then are stuck with a 46x24 ring/cog as there are no larger rings for 104mm cranks and no other Alfine options. But the extra real estate the slightly longer shell provides will make it easier for the tire/stay/ring to share space. And that becomes really important, as you already know, since you are tied to a chainstay length. And the recommended adjustment length might not bridge the gap between the belt sizes. And might not even allow a different belt/cog/ring combination to work for the sizes you choose to design around.

CS length, is determined by your belt/cog/ring choices. The tool on Gates' site will take your cog ring and give you the CS lengths that will work for the three belt sizes.

CS type; Stiff, the new CenterTrack cog/ring/belt are much more tolerant of misalignment than the older system....but that system was absolutely intolerant so it's a relative thing. The rear end has to be stiff or the belt could skip under power, which is why Rohloff requires frames to be tested for stiffness before they will sell a belt cog to you.

The thing to watch for with dropouts is that the belt needs quite a bit of tension, so some kind of set screw is nice. And that the drop/ebb has to hold that tension, getting loose is unacceptable. Also that 24T belt cog is wide and sits relatively outboard and might interfere with the drop/stay depending on design.

Cranks; With an Alfine where there isn't much ability to adjust the belt line, a crank/bb that you can adjust that is necessary. So a Phil square taper or most of the outboard bearing cranks offer that. If the customer is really attached to their octalink cranks you have to adjust the chainline with bb spacers or facing.

I've been dragging out a somewhat similar build for a while because I've donated extra brain time and eyeball engineering towards getting a belt to work with studded 700x42 tires/fenders/68mm EBB/56x22 belt. The user wants a SS and that's the only belt setup that comes close to the ratio needed.


----------



## bikecycology (Apr 26, 2010)

*A couple of design elements*

Whit,

Consider using the toggle dropout from Paragon. They have limited quantities until after NAHBS but it will help a lot with belt tension issues.

Also, Gates has rear CDX sprockets in 22t, 24t, and 26t

There are also several offerings for front rings in 4x104 (given the thought to switch to mountain cranks over road)

- Gates Carbon Drive Belt System


----------



## Meriwether (Jul 26, 2007)

Thanks guys, I appreciate the help. I didn't think this was going to be a very challenging build but it's turning out to be a lot of little things adding up.

Switching to a 104 crank is a good call. I'm going to show my ignorance here but i thought you couldn't use a 73 shell and MTB crank with a belt-drive Alfine since the chainline of most MTB's is 47 to 50 and the Alfine belt is 44.85 ? 
A road double is usually around 44 which would get me pretty close. 

What am I missing? 

I could see getting that to jive using a square taper but he wants to use an external cup BB, though is not stuck on a road crankset.
As this bike will be primarily a commuter and secondly a gravel touring bike, i think a 46/24 should be fine?

The Toggledrop is very cool looking but the guy i'm building the bike for doesn't want to be on the bleeding edge I think. I trust PMW a lot, but seeing as it's not out yet to the public and there's no mention of price...we probably will have to pass. 

I am planning on using TT's HSBENDCS1MAG with 1.4/ 0.9 wall and straight gauge 16mm seatstays so I hope that'll be stiff enough.


----------



## BungedUP (Aug 18, 2003)

Meriwether - 

I've built several Alfine frames, some belt drive. I can't remember chainstay length exactly, though 455 mm comes to mind (I can't remember if that's correct for those bikes or not- I see a lot of stuff and after awhile some of it blends together). I'm at the dinner table and don't have anything directly in front of me that jogs my memory, but it seems like there is always trouble with getting ring clearance on Alfine related belt-drive stuff. We've done dimpling operations, sometimes mitering out a section of stay and welding in another tube, and I recall having flipped stays and put them in "backwards" (bends going opposite to normal orientation). IIRC that last solution worked really well for at least one frame I built, but that was for 32C+fender clearance, and I think there was a touch of dimple added after the fact for the tire. 

My coworker made a little gauge, which bolted to the post that fixtures the BB shell. There is a corresponding measuring reference, which is basically a BB shell with a bar welded to it, parallel with the shell face. You can install the reference gauge to the crank, take measurements at the chainring and pedal end, and then reference those measurements to the other gauge, which is a just another reference feature running parallel to the actual shell in the jig (I'm doing a terrible job explaining this, but my daughter is talking to me while brushing her teeth). Anyhow, but using this gauge, you can play with inset and with adding bend to chainstays until you get something that works. We often add bend to chainstays with a fork raker-type device until things fit (when possible). 

I don't think that you need any particularly strong chainstays - we typically end up using a single bike road chainstay, along with 5/8 X.028" seatstay material, and that seems to work. The Rohloff stuff almost always ends up using tandem stays, but I think that's just because of the bike models it ends up on. 

I hope there's something useful in there for you.

-Peter


----------



## Saul Lumikko (Oct 23, 2012)

Are you sure you need to dimple the chainstay to make the front ring fit? These things are far smaller in diameter for the tooth-count compared to regular 1/2" pitch chainrings.

One BB that allows you to adjust chainline quite precisely is the GXP. Sideways play (and position) is entirely controlled by the left side bearing cup, so adding or removing spacers there will alter your chainline. With a single chainring for 1X setups the chainline is 47.5 mm when the cranks are centered, but the inner one of double rings should be a bit more inboard.


----------



## Meriwether (Jul 26, 2007)

BungedUP said:


> Meriwether -
> 
> I've built several Alfine frames, some belt drive. I can't remember chainstay length exactly, though 455 mm comes to mind (I can't remember if that's correct for those bikes or not- I see a lot of stuff and after awhile some of it blends together). I'm at the dinner table and don't have anything directly in front of me that jogs my memory, but it seems like there is always trouble with getting ring clearance on Alfine related belt-drive stuff. We've done dimpling operations, sometimes mitering out a section of stay and welding in another tube, and I recall having flipped stays and put them in "backwards" (bends going opposite to normal orientation). IIRC that last solution worked really well for at least one frame I built, but that was for 32C+fender clearance, and I think there was a touch of dimple added after the fact for the tire.
> 
> ...


Peter, 
thanks for the help, you're pretty good at multi-tasking!

I like the flipping the chainstay idea, i'll see if that'll work with the ones i plan on using. I may be hard pressed to get a 40 tire in there too without dimpling on both sides too much. It's good to know that the Alfine may not need as stiff a rear triangle as the Rohloff.

The "Gates_Tech Manual_Eng_Apr2013.pdf" shows a drawing of a bike with a 68mm BB shell, Centertrack belt, Alfine 8, and notes a required 44.85mm chainline to match the rear cog's chainline. That means that the (X,Y) of this setup to the INSIDE of the front cog is about (39.6, 80) = 80mm diameter ring that's 39.6mm from frame centerline (ring is about 11mm wide). So you can probably use a MTB crank with a 50mm chainline on a 68 BB shell and match the 44.85 required belt-line by moving spacers off the driveside cup but you still have to get that narrow chainline the Alfine requires. A smaller ring would help but for a townie I wouldn't want to go under a 46.

For the crank gauge thingy, is the attached similar to what you were describing? I copied Joel of Clockwork's design on mine and it's great. But you do have to miter the stays first a bit longer to make sure it all jives before doing the final length cut.


----------



## Meriwether (Jul 26, 2007)

Saul Lumikko said:


> Are you sure you need to dimple the chainstay to make the front ring fit? These things are far smaller in diameter for the tooth-count compared to regular 1/2" pitch chainrings.
> 
> One BB that allows you to adjust chainline quite precisely is the GXP. Sideways play (and position) is entirely controlled by the left side bearing cup, so adding or removing spacers there will alter your chainline. With a single chainring for 1X setups the chainline is 47.5 mm when the cranks are centered, but the inner one of double rings should be a bit more inboard.


Saul,
Thanks for the help.

The belt rings are smaller in diameter for the same chainring tooth count but I'm pretty sure there will need to be a dimple because of the 46t ring for the Gates is just under 80mm and the distance from the BB center is only 39.6 to the inside of the ring to get that 44.85 chainline. 
When looking at other builders bikes, say Co-motion, that does a lot of these types of bikes all have big dimples on the outside of the chainstay. Per BungedUp, it sound like with a 455 CS length you can fit fenders and a 34 tire with some dimpling.

I think using a 68 shell and a 104BCD crank would work and give more lateral chainline adjustment than using a 130BCD road crank but it really doesn't matter in this case because of the gear ratio he needs for this bike and the fact that Gates only makes a 24t rear cog for the Alfine hub (46t is the only front ring that'll work and it has to have that 44.85mm chainline).


----------



## Meriwether (Jul 26, 2007)

So I've seen outside dimples on chainstays for ring clearance and have done them before. 
But do you think cutting out a piece of the chainstay and brazing on a concave cap would be stronger? 
My gut says yes unless it's a big cut-out piece. 
Do any of you have any experience or hearsay to share?


----------



## Meriwether (Jul 26, 2007)

bikecycology said:


> Whit,
> 
> Consider using the toggle dropout from Paragon. They have limited quantities until after NAHBS but it will help a lot with belt tension issues.


From Paragon's website, "The ToggleDrop is only compatible with a Shimano 142 x 12 mm skewer that has been modified to fit the dropout by Paragon Machine Works."

So that won't work with Alfine hubs or Rohloff hubs.


----------



## irrah (Dec 18, 2008)

Meriwether said:


> I think using a 68 shell and a 104BCD crank would work and give more lateral chainline adjustment than using a 130BCD road crank but it really doesn't matter in this case because of the gear ratio he needs for this bike and the fact that Gates only makes a 24t rear cog for the Alfine hub (46t is the only front ring that'll work and it has to have that 44.85mm chainline).


You missed this ? Maybe You will get more options for Front Sprocket size.



bikecycology said:


> Gates has rear CDX sprockets in 22t, 24t, and 26t


Universal Cycles -- Gates Carbon Drive CenterTrack Rear Cog


----------



## Meriwether (Jul 26, 2007)

irrah said:


> You missed this ? Maybe You will get more options for Front Sprocket size.


I just thought he was wrong...damn, i did miss that major detail! I read somewhere that there were only 24t cogs for the Alfine and it stuck in my head. Seems like that is old or bad information. Thanks for pointing out the obvious, that'll help a bunch.
I checked the Gates site for verification:
- Gates Carbon Drive Belt System


----------



## bikecycology (Apr 26, 2010)

Meriwether said:


> From Paragon's website, "The ToggleDrop is only compatible with a Shimano 142 x 12 mm skewer that has been modified to fit the dropout by Paragon Machine Works."
> 
> So that won't work with Alfine hubs or Rohloff hubs.


Doh, missed that part. Sorry.

I'm interested to see where this goes. I know G-reg has his head wrapped around what he has going on. Looking forward to seeing that thing all set up.

Keep us posted!


----------



## bikecycology (Apr 26, 2010)

Meriwether said:


> I just thought he was wrong...damn, i did miss that major detail! I read somewhere that there were only 24t cogs for the Alfine and it stuck in my head. Seems like that is old or bad information. Thanks for pointing out the obvious, that'll help a bunch.
> I checked the Gates site for verification:
> - Gates Carbon Drive Belt System


Whit,

I would call Gates directly. I deal with a guy there named Steve Pardoe. He should be able to give you some good advice/help.

Also, this is an example of a cutout I was talking about earlier. I see no structural downsides to this. You shouldn't get any more flex from it than you would without it.









Here is the post on Dimitri's blog. MEECH Custom Bicycles: Custom Chain Ring Clearance

Hope it's helpful, Wil


----------



## smudge (Jan 12, 2004)

bikecycology said:


> Whit,
> 
> I would call Gates directly. I deal with a guy there named Steve Pardoe. He should be able to give you some good advice/help.
> 
> ...


The cross sectional width has been reduced in the beefiest area of the stay. I do believe that it will flex more.

take it with a grain of salt. I haven't put it on a test rig and I don't have any data. BUT Neil at Cycle Monkey told me that several frames have failed the Spot/Rohloff test even without chainstay cutouts.

The Centertrak system has much less tension than the old system but it still pulls the back end toward the drive side somewhat.


----------



## G-reg (Jan 12, 2004)

Meriwether said:


> I just thought he was wrong...damn, i did miss that major detail! I read somewhere that there were only 24t cogs for the Alfine and it stuck in my head. Seems like that is old or bad information. Thanks for pointing out the obvious, that'll help a bunch.
> I checked the Gates site for verification:
> - Gates Carbon Drive Belt System


I stand corrected, 22/24/28 seem to be out there. QBP is my usual source for all things bike nerd and they still only list the 24 as an option. There's still a small range of gear ratio/chainstay length/belt length you have to operate in.

There was a MTBR'er who cut the hell out of a drive side CS and brazed in a hunk of steel as bickeology posted. I'll look for the thread but if I recall correctly he had some stiffness problems.

Found it: TimT..TimT to the white courtesy phone


----------



## Meriwether (Jul 26, 2007)

I have an email in to Steve at Gates, i'll report back my findings. I'm sure i'm the only one interested now but it'll be another post to search for future builders.

I also found Rody's way of doing the cut-out:
Groovy Cycleworks 330-988-0537: Martin's build...day 3 through ???
I'm sure with the Centertrack the rear end stiffness is less of an issue but always best to be on the stiff side.

BTI also only has the 24t Alfine too, so that's another reason i thought that was all they offered.


----------



## bikecycology (Apr 26, 2010)

Meriwether said:


> I have an email in to Steve at Gates, i'll report back my findings. I'm sure i'm the only one interested now but it'll be another post to search for future builders.
> 
> I also found Rody's way of doing the cut-out:
> Groovy Cycleworks 330-988-0537: Martin's build...day 3 through ???
> ...


I'm very much interested in what you come up with. I'm also looking forward to seeing Greg's build.

A good bike to look into for answers in the Tout Terrain Amber Road. My friend has one that is set up with Alfine 8, belt drive and I believe it can fit 42's or 45's. I don't remember if the drive side chain stay is full length of if they have some fashion of plate in there for clearance but it might be worth looking at.

Looking at the website now confirms that it does have a clearance plate.

Amber Road


----------



## Meriwether (Jul 26, 2007)

Here are the answers I got from Gates to my pretty basic questions on the system. Hope this helps others.

> - What is the correct belt-line for the Alfine 8 and the CenterTrack belt? 
- The Alfine 8 had a belt line of 43.6mm

> What is the the minimum distance between the inside of the front chainring and the center of the BB? 
- Assuming you had perfect alignment the inside edge of the sprocket would sit at 38.1mm and then you would actually want 2mm more for frame clearance. I suggest your dimple is a maximum of 36.1 from the center line. The CenterTrack system still operates well up to 2mm out of alignment.

> - Are there any external bearing (i.e., GXP) cranksets you recommend using that work better than others and that are flexible in micro-adjusting the chainline?
- They are all good. I prefer X-type because you can space them if necessary. The GXP cannot be spaced since it located of the non-drive side cup.


> Say I'm using Paragon Sliding dropouts, a 46/24 ring combo, and want to choose the 115 length belt. That gives me a chainstay length of 438mm. The Gates PDF says 12mm minimum belt adjustment. Does this mean i set the chainstay length at 436 or 428 with the sliders all the way forward to allow it to tension to 438mm with the belt loaded? Or do i set the length at 438 and the actual tensioned chainstay length will be over 438?
- Gates makes this unclear. You can disregard this because you are using sliding vertical drop outs. This only applies to bikes using horizontal drop outs. For your application I would just make sure you get as many combination out of 1 belt that you can.

> I've seen what other bikes out there come stock with but I'm wondering what cog choice you'd recommend for an Alfine 8 commuter and occasional tourer? 46/24 or 39/22 or ? I know a lot depends on the rider and terrain, but what do you see in general for this type of bike?
- With the 8 I would suggest 50x24. 46x24 is the lowest you can go because of Shimano's recommended lowest input ratio.


> What do you see fail more at the chainstays? Chainstay dimple or a cut-out with a concave plate brazed on? What do you recommend using?
- I see a lot of everything. I've seen dimples crack but I have see good luck with yokes and brazed on (caps).


> Do you have any experience using Paragon Rocker dropouts without tension screws? Do they work well for the Centertrac belt system? These are desirable for the position of the disc brake caliper and the ease of running fenders and a rack.
- I think you will need the tension screws to get adequate tension on the belt.


----------



## G-reg (Jan 12, 2004)

Meriwether said:


> ......
> 
> > - Are there any external bearing (i.e., GXP) cranksets you recommend using that work better than others and that are flexible in micro-adjusting the chainline?
> - They are all good. I prefer X-type because you can space them if necessary. The GXP cannot be spaced since it located of the non-drive side cup.
> ...


1234


----------



## 18bikes (Jan 15, 2007)

I'd not really been paying this thread much attention but I've recently had an enquiry that makes this very relevant. 

My customer would like the option of running a belt even if he doesn't do it straight away. I have no issue with the splitter or dropouts but I think I'm going to have a tyre clearance issue. The frame will be an MTB needing clearance for at least a 2.2 tyre. Every MTB we've done with an Alfine (our frames and other brands through the shop) has had a 32-38t front chainring in middle ring position on a standard MTB chainset with no messing with spacers either on the ring or BB. At the back we use the dished cogs mounted the 'wrong' way round to increase the chainline. This has always lined up really nicely and doesn't cause any problems although I *think* (not looked at the dimensions) there is a slight misalignment. 

It looks to me that Gates don't offer a dished cog so I can't run it how I normally would, has anyone built something with this kind of tyre clearance successfully?

Matt


----------



## 18bikes (Jan 15, 2007)

Ah, I've just found the Alfine Di2 cog, which looks to have the same dish as the chain cogs so maybe ignore my post


----------

