# Carbon Drive Systems



## Team Fubar Rider (Sep 3, 2003)

I searched this on the forums and didn't see anything, so if this is old news, I apologize...

Anyhoo, I sent an e-mail to Gates (the makers of the Carbon Drive Systems) regarding their belt drive for the non-drive side for tandems. The e-mail I got back said they were currently working on the dimensions of the belt and then should have it out shortly after. 

I think for the non-drive side of a tandem, this would be AWESOME! No lubing, quiter running, no wear, just replace the belt every so often and you're set. 

I know there would be some drawbacks, like if you break the belt on a ride you're screwed, but I think the ease of maintenence would greatly outweigh the few drawbacks.

What do you think?


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## PMK (Oct 12, 2004)

Co-Motion is already doing it. It's an option which is supposedly available now. Not cheap at over $500.

PK


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## Team Fubar Rider (Sep 3, 2003)

I doesn't sound like they are completely a go with it yet, still some size issues with the belt to be worked out.

I am more interested (and that is what I inquired about) retrofitting it/aftermarket to an existing tandem, mainly mine!


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## PMK (Oct 12, 2004)

I guess the point is that they have made pulleys, different tandems will possibly need different length belts.

It seems they are all in as the belt drive is standard stuff on their race and high end bikes and an option on others.

http://www.co-motion.com/information/faq/carbondrive.html

http://www.co-motion.com/custom_bikes/features_options.html

http://www.co-motion.com/tandem_bikes/robusta.html

I would guess that if you called Co-Mo and got the dimension from BB to BB centers, you could see if their belt had the proper tooth count / length.

I am intrigued, but not committed.

Just some thoughts

PK


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## TandemNut (Mar 12, 2004)

I wonder how the belts will fare under off-road conditions? Mud, water, grit, etc. 
Also, what happens to the belts when we high-center on a log crossing? Does it stretch, and does repeatedly stressing the belt like that have some detrimental effect?
Road motorcycles like Harley Davidson have belt drive, but the off-road motorcycles stay with chain drive.


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## Team Fubar Rider (Sep 3, 2003)

Supposedly, they have added more "holes" to the teeth of the cogs to clear mud better. 

That is the type of stuff I wonder about, like will it stretch out on a log/rock crossing and then you're stuck.


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## itsdoable (Jan 6, 2004)

PMK said:


> I would guess that if you called Co-Mo and got the dimension from BB to BB centers, you could see if their belt had the proper tooth count / length.


The specs are at the link above:


> Gates Carbon Drive Checklist
> If your tandem meets these criteria, the Gates Carbon Drive may work for you
> - 28.5"/724mm boom tube length (measure from rear bottom bracket to front bottom bracket)
> - Tandem crankset with 130mm BCD timing crankarms
> ...


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## TandemGeek (Mar 14, 2004)

This time from our Bulletin Board Archives.... more general info on the Gates Carbon Drive for tandem crossover drives.



> *27 Sep * Co-Motion Replaces Sync Chains With Gates Belt Drives* - Co-Motion Cycles has introduced a productionized Gates belt drive system that replaces the traditional timing rings & sync chain and is beign offered on their high-end racing tandems. The cited advantages include a 283 gram reduction in weight compared to a sync chain system, increased service life, and nearly maintenance-free operation. We first learned of the belt drive from a friend at the Southern Tandem Rally before Interbike opened who had discussed the new system with the folks at Co-Motion. With a little sleuthing, we were able to locate some photos of the system, which you can find linked HERE. A good friend, Bob T. from Florida, had previously developed and produced his own working prototype 'sync belt drive system' several years ago which has worked very well for him. It will be interesting to see how the production model performs, how it is embraced by consumers, and any spin Co-Motion's competitors might put on the system.
> 
> *04 Oct * Co-Motion Replaces Sync Chains With Gates Belt Drives *(Updated) - As mentioned last weekend, Co-Motion Cycles has introduced a productionized Gates belt drive system that replaces the traditional timing rings & sync chain. In addition to the photos posted of the Macchiatto displayed at the convention center last week, some new photos of the system installed on a Periscope Torpedo have emerged. From Co-Motion's Blog it was noted the introduction of the sync belt system is an exclusive collaboration between the folks at Carbon Drive / Gates and Co-Motion Cycles. Also as previously noted, Co-Motion will be offering the new timing belt system as standard equipment on their top 3 race tandems: Macchiato, Robusta and Supremo. However, as evidenced by the belt-equipped Torpedo, Co-Motion will also offer the belt system an upgrade on many of their other tandem models. The cited advantages include a 283 gram reduction in weight compared to a sync chain system, increased service life, and nearly maintenance-free operation. For kicks I weighed just the sync chain on our Erickson tandem tonight and it was 437 grams whereas the two 71t gear pulleys (aka, drive rings) and belt that comprise the Gates Carbon Drive system weigh just 363 grams!! Price? According to WebCyclery, the belt and two pulleys sell for $525.
> 
> _For those interested in ease-dropping on some on-going technical dialog regarding the pros and cons of belt vs. chain drive systems, you can find a lively but very civil discussion thread at [email protected] (tandem enthusiast listserve) by clicking HERE. The thread is chronological, beginning at the top of the search page with item number 3 by Mark Livingood on 10/5/2008. A companion thread can be found HERE and, as before, is chronological beginning this time with Item #4 posted by Bill Franklin on 10/6/2008._


A good friend up in Bend, OR, who works for WebCyclery already has a set installed on their Macchiatto and he provides his comments on the installation, performance and a bunch of photos at this BLOG entry.


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## TandemGeek (Mar 14, 2004)

BigNut said:


> I wonder how the belts will fare under off-road conditions? Mud, water, grit, etc.
> Also, what happens to the belts when we high-center on a log crossing? Does it stretch, and does repeatedly stressing the belt like that have some detrimental effect?
> Road motorcycles like Harley Davidson have belt drive, but the off-road motorcycles stay with chain drive.


Water's not a big deal but I'm not sure I'd want to put them on our off-road tandem, having watched quite a few sticks and what not kicked up by the front wheel get sucked into the sync chain where they would (usually) get chewed up by the rear timing ring and chain. I'd also be concerned about other debris that gets kicked up by the front wheel and that's too large (and/or too hard) to be pushed through or crushed at the merge of the pulley and belt. The latter are the same reasons that belt drives haven't been widely used on dual-sport motorcycles. However, that said, BMW broke new ground and put a nearly-enclosed belt drive on it's F800 and it seems to work just fine. So, I guess if someone wanted to put an enclosed belt-drive on their off-road tandem... yeah, right.

I also don't believe "stretching" is an issue because these carbon-reinforced belts just don't stretch: you install them with just enough preloading to keep them from skipping between a set of equally off-set pulleys and away you go. Now, the problem that could surface on an off-road tandem would be getting the belt shoved out of alignment to where it derails as it's dragged across a berm, log, rock or otherwise bumped from the side in technical single track. Unlike a chain which you can usually roll-on and off the chainrings if you leave about 3/4" of slack, you'd have to undue the eccentric to create enough slack to get your belt back on.

The last issue would be durability and cost. The pulleys and belts aren't cheap and based on all of the foregoing issues that would be unique to off-road tandem use as a sync belt system, I would venture a guess that you'd tear up pulleys and belts about as fast as chains and chainrings if used in truly technical off-road conditions. So, the cost benefit that the belt system might enjoy due to it's low-maintenance / long life on a road tandem is quickly diminished.

Anyway, those are my thoughts.


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