Why don't derailleurs exist for belt driven bikes?
Just what the title says. Why isn't this possible? I would love a quiet and smooth belt drive on my bike.
Posted Apr 9, 2016, 4:48 AM UTC
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It would be really hard for a belt to roll from one gear to the next if belts were used with external gears. Further, belts need to be wider to be as strong as a chain. So you wouldn't be able to stack up many gears/cogs when each needs to be 10+mm wide. Therefore a derailleur system is just impossible.
ab results have said concluded that a belt is slightly less efficient (not enough to be realized) or that there is no loss in efficiency. You can read either report and make your own decision, but as someone who rides (and makes) belt drive bikes, I love them. I've never met a cyclist who rode a belt drive bike and said they were less efficient in reality.
Belt drives do require more precision in the frame (can't be off more than 2 degrees from bb to dropout) and yes the frame must have an opening for belt replacement. The silent and smooth drive is amazing, and belts have a significant reduction in cordial action - helps knees. Further belts, and internal gear hubs are incredibly low maintenance.
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Oh yah I didn't think about the width!
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The nature of the belt because its unbreakable unlike a chain and you can't just put a belt on anybike you have to split a seat or chain stay to put it through the frame and rear cog to fit a belt teeth, a belt going thru a derailleur would just be a mess.
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That doesn't matter at all. Regular chain derailleur cages can easily be disassembled and installed over an existing chain. Or removed from one. Last time I changed someone's rear mech without breaking the chain they looked at me as if I had performed a miracle.
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If you want a belt drive you get an internal geared hub like Shimano Alfine, Rohloff, or Sturney Archer.
A belt with derailleurs might be prone to damage from the derailling action.
Another idea for belts is this: https://en.wikipedia.org/wiki/Continuously_variable_transmission
Interesting. I know that internal gear hubs lose a little more power than a typical chain and derailleur setup. I imagine a transmission of some kind would necessarily lose power, or add weight?
Yes. If you want maximum efficiency and light weight, you use a chain.
The advantages of belt drive are low maintenance, cleanliness and quiet operation.
The disadvantages are reduced efficiency, the need to "break" the rear triangle, and increased weight.
The main source of inefficiency of a belt drive is that it needs to flex. If you designed a derailleur system for belt drives, you'd introduce more bending and more inefficiency.
In the end, internal gear hubs, while slightly less efficient than a chain and cassette/derailleur system, would be many times more efficient than a hypothetical belt derailleur system.
There is no drive system more efficient than the cog/chain system used in traditional drivetrains. In a well maintained system, mechanical losses are negligible.
until you need to re tension your belt
like a chain guard
because chain noise is the number 1 thing people hate about cycling.
You forgot cost. They cost considerably more. Plus you might be screwed if your belt snaps and you don't have a spare as not all shops stock them.
Yup