What Is an E-Bike Belt Drive?
What is a belt drive, in plain words?
It's a bicycle drive with a belt where the chain would be. Wikipedia calls it a chainless bicycle that uses a flexible belt, typically toothed, to carry power from pedals to wheel.1
A chainless bicycle is any bike that moves power to the wheel by some means other than a metal chain.2 A belt is one of those means. Shaft drives are another.
The rest of the bike looks familiar. You still have pedals, cranks, a frame and two wheels. The change is in the loop that links the front of the drivetrain to the rear wheel.
What is the belt actually made of?
One cycling site describes it as a loop of polymer with moulded nylon teeth, reinforced by carbon fibre tensile cords.3 "Tensile cords" are the strong strands buried inside the belt that stop it stretching when you pull on it.
That explains the name "carbon belt drive". The carbon is in the cords, not the whole belt.
The belt runs on toothed cogs. A cog is the toothed wheel the belt wraps around. One sits at the pedals and one sits at the back wheel.
Can an e-bike have one?
Yes. Wikipedia lists belt drive among the ways electric assist can be added to almost any pedal cycle.4 So the belt and the electric motor are separate choices. A bike can have a belt with a motor, or a belt without one.
Which motors suit which bikes is a question for the bike's maker. The page on belt drives with hub gears and motors goes through what the sources say.
What does a belt change about the bike?
Quite a bit, mostly in the frame and the gears.
Gears. Derailleurs can't be used with a belt, so a hub gear is used when you want more than one gear ratio.1 A hub gear keeps its gears sealed inside the rear wheel hub. A derailleur is the arm that moves a chain across a stack of cogs.
Frame. A chain can be split open and put back together. A belt generally can't. Because belts are a single continuous loop, the frame must include a split in the rear triangle to allow installation.3 The page on why belt drive frames have a split explains this further.
Length. Belts come in a limited selection of lengths, and the frame has to be designed around them.1 You can't just add or remove a link to fix the fit.
Upkeep. The same cycling site says there's no need for lubrication or degreasing.3 Care still matters, though. See cleaning and caring for a belt drive.
Why do people ask about belt drives on e-bikes?
Wikipedia lists little to no maintenance among belt drive benefits.1 This site doesn't rank belts against chains, and it doesn't say one suits you better. It explains what the makers and reference pages say, so you can read your own bike's manual with some background.
Looking at a bike with a belt? Check the maker's manual for the tension setting and any limits on the motor. Those details differ from bike to bike.
Cited material
- Belt-driven bicycle, Wikipedia
- Chainless bicycle, Wikipedia
- Carbon belt drive, everything you ever need to know, Cycling About
- Electric bicycle, Wikipedia
Keep reading
How a Belt Drive Works: Belt, Front Cog and Rear CogThe parts of a belt drive and how they move the wheel, from the toothed belt and its cords to the cogs, the hub gear and the alignment between them.
Why Belt Drive Frames Have a Split or OpeningA belt is one closed loop, so the frame needs a gap or removable section to fit it. Here's where the split goes and what makers say about it.
Belt Drives with Hub Gears and MotorsWhich gear systems and e-bike motor types go with a belt drive, and what reference sources say about mid-drive and hub motors.