Almost all the world’s bicycles use Victorian technology for the drivetrain: the roller chain, invented in 1898. Every other option is niche. Direct drive, where the pedals are attached to the wheel, is restricted to penny farthings, unicycles, and children’s tricycles. Shaft drive has never taken off. Treadle drive and string drive are novelties. Only one alternative looks likely to stick: belt drive. Here’s why you might want to choose a belt over a chain – and why you might not.
- Can be separated and rejoined. This doesn’t sound like a big deal until you consider that, on any bike with conventional chainstays, the chain loops through the frame between the chainring(s) and sprocket(s). If you couldn’t separate the chain, you’d have to separate the frame instead, designing it to bolt together on the drive side. That’s how frames for belt drive bikes work, and it makes the frames more expensive and slightly weaker. Furthermore, a snapped chain can be rejoined, whereas a snapped belt goes in the bin. You can lengthen or shorten a chain by adding links, so you’re free to fit different sized chainrings and sprockets; a belt drive will work only with specific combinations.
- Works with derailleur gearing. Belt drives don’t. With a belt, you can have only one chainring and one sprocket. That means non-variable, singlespeed gearing, or more expensive internal gearing in the hub or bottom bracket.
- More efficient. At their best, chain drives transmit almost 99% of the power that goes into the pedals to the rear wheel. Belt drives aren’t this good. They’re getting better but the difference can be felt.
- Ubiquitous and cheap. If you need a new chain, you can get one from any bike shop in any town in the UK. New belts need to be ordered and are twice as expensive (or more).
- Doesn’t need oiling. A chain needs lubricating to work at its best and not go rusty, and this lubrication can end up all over the inside leg of your trousers or on the floor of your hallway. A belt drive runs dry and clean, and is pretty much fit-and-forget. This is a big deal for non-technical owners.
- Quieter. A metal chain meshing onto metal sprockets and running through derailleurs makes quite a bit of noise – noise you’re only really aware of if then ride a belt-drive bike, which is almost silent.
- More durable. Chains get longer as their pivots wear away, and the gearing performance deteriorates. If you don’t replace chains by the time they’re 0.75% longer, you’ll probably need to replace the sprockets and chainrings too. Belts stay the same length. Their performance doesn’t degrade. They cause minimal wear to the chainring and sprocket, since the belt isn’t metal. And they work fine until they eventually snap – having clocked up perhaps twice as many miles as a chain.
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