# Can a tensioner be used with belt drive?



## notso (Jan 22, 2015)

So I had a chance to ride a belt drive single speed for the 1st time about a week ago. It was really cool and has me thinking that I should build something as a project...

I currently have an old Alpine Stars Cro-mega that has a rear triangle shape that would accommodate a belt without cutting the seat stay, but it has vertical dropouts. Can I just slap a tensioner on there?

Also, How much does the Gates belt drive system usually cost (ballpark)?


Thanks!


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## formula4speed (Mar 25, 2013)

Someone with more technical knowledge but I'm pretty sure you can't. First because belts require a high level (and specific levels) of tension. On top of that you have to be careful not to "kink" the belt.

Maybe you could run an EBB?


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## SeaBass_ (Apr 7, 2006)

If you could source a pulley and graft it onto a tensioner it might work. You would need a strong spring for proper tension methinks.


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## mack_turtle (Jan 6, 2009)

I have worked on a few belt drive bikes and I am aware of the special tool you're supposed to use to check the belt tension. it has to be within a specific range, but _I suspect that is for internal gear hubs to work_. I cannot say with certainty that singlespeed drivetrains require the same amount of precision.


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## Cotharyus (Jun 21, 2012)

mack_turtle said:


> I have worked on a few belt drive bikes and I am aware of the special tool you're supposed to use to check the belt tension. it has to be within a specific range, but _I suspect that is for internal gear hubs to work_. I cannot say with certainty that singlespeed drivetrains require the same amount of precision.


The tension range is for the belt itself. There are also certification processes that frames have to go through to be approved by Gates for belt drive use - there are very specific limits to how much the frame is allowed to flex, because the belt can (and will) walk off the pulleys. Cogs. The...things that it turns on. Maybe Andrea will pop in and comment on this. Barring that, she talks about some of the challenges of belt drives on a recent JRA episode. She's a mechanic and a Gates sponsored single speed racer, so she kinda knows her stuff.


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## mack_turtle (Jan 6, 2009)

thank you for clarifying. yeah, I would *not *mess around with putting a belt drive on a bike that was not designed for it.

look at the Trek Stache- people reporting that chains are popping off of singlespeed drivetrains under load because the chainstays flex too much. I'll bet the problem woud be much worse with a belt.


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## WillTheGreat (Aug 26, 2010)

SeaBass_ said:


> If you could source a pulley and graft it onto a tensioner it might work. You would need a strong spring for proper tension methinks.


Yes you would need significantly more tension than a typical single speed chain tensioner could provide. It would need to be pretty big and heavy to work, so not very practical. To give a sense of scale, I would guess it may need to be as big as an engine timing belt tensioner.


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## Velobike (Jun 23, 2007)

mack_turtle said:


> thank you for clarifying. yeah, I would *not *mess around with putting a belt drive on a bike that was not designed for it.
> 
> look at the Trek Stache- people reporting that chains are popping off of singlespeed drivetrains under load because the chainstays flex too much. I'll bet the problem woud be much worse with a belt.


I can speak to that. I have been fiddling around with belt drive for over 20 years. First efforts were with V-belts. 

A bike designed for a chaindrive does not need the same precision that a belt drive bike needs with respect to the chainline. Also part of the 'feel' of a bike is actually down to a bit of lateral flex in the chainstays. This feature is not a problem on a bike using derailleurs which have guides to keep the chain on the sprockets.

I have attempted conversions on a number of bikes, about half were failures. Those that did work were generally designed for singlespeed use so the chainstays tended to have less lateral flex - there's no guides to keep the chain on.

As for tension, I ignored the guidelines for tension because I felt that I would be sacrificing the bearings on the BB and the wheel by chasing optimum belt tension. I found that with a perfect chainline I could use tension only slightly more than a chain on a bike with a hubgear. On a singlespeed i found that more tension was needed which was unacceptable to me, but the problem was solved by the use of a snubber at the 7 o'clock position. The snubber being positioned about 1mm above the belt so it only came into play if the belt started to rise on the sprocket.

I never went past the first version of the Gates belts because I felt I was chasing an illusory benefit, but I am sure the later version with its better tracking probably gets rid of most of the problems.

A singlespeed with a belt drive is remarkably silent. You start hearing little noises on your bike you never noticed before. However at the moment I would only consider it for a bike used mainly for road or gravel, ie clean riding.

As a singlespeeder I like the fact that getting rid of a belt gets rid of about 110 little moving parts and replaces it with one, the belt.


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## notso (Jan 22, 2015)

Thanks for the insights. I had ridden the A-stars to an LBS a couple years back and someone walked in and said to one of the guys working in there "did you see that bike outside? It would be perfect for belt drive". That combined with my recent 1st SS MTB experience on a belt drive raliegh got me thinking....


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## banks (Feb 2, 2004)

Frame stiffness is Key! If not stiff enough, the belt will come off at the worst possible time.
You need to measure the chain stay length to find out if you can use Gates Carbon Drive system, as there are few combinations. Not cheap! Tech Resources
Gates Carbon Drive Centertrack system you might be able to use a 'snubber' if you found a working combination. I would not recommend it, and Andrea agrees before her first after work shift beer.


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## AlexBiking (Feb 12, 2018)

Veer actually makes a single speed belt conversion kit that includes a tensioner. They don't require as much tension as the Gates system so it might be a good solution on your Alpine project. It's about $350. https://www.veercycle.com/products/synchronous-belt-conversion-kit-for-multi-speed-bike-frames


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## junglejim86 (Jan 10, 2006)

the trek district 3i used to come stock with a belt and tensionser


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## Krnk4wrd (Dec 23, 2020)

formula4speed said:


> Someone with more technical knowledge but I'm pretty sure you can't. First because belts require a high level (and specific levels) of tension. On top of that you have to be careful not to "kink" the belt.
> 
> Maybe you could run an EBB?





formula4speed said:


> Someone with more technical knowledge but I'm pretty sure you can't. First because belts require a high level (and specific levels) of tension. On top of that you have to be careful not to "kink" the belt.
> 
> Maybe you could run an EBB?


had a Raleigh belt drive ebb , so so ?
The kink comment , most of us know the lay of a belt , it only goes one way , gates says that once it's bought , it's yours . THEY WILL NOT TAKE IT BACK . Sealed , in the packaging , in the box ! SOME GUARANTEE ?


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