Also called: center motor, crank motor, drive unit
What it does
It drives the chain, so it uses the bike's gears like your legs do. That makes it efficient on hills. Bosch, Shimano, Yamaha, Brose and Bafang's M-series are mid-drives.
Signs of a problem
- Faster chain and cassette wear than a regular bike
- Grinding or knocking from the motor area
- Assist that feels uneven when you pedal (often the torque sensor)
Safe things to check
- Check the cranks are tight and don't wobble.
- Listen for noise with the power off while turning the pedals backward.
Looking after it
- Shift to an easier gear before stopping and before steep climbs; easing off the pedals as you shift is kinder to the chain.
- Replace the chain before it wears the gears out.