Home mechanic (basic tools) ยท Time: 15 to 30 min (estimate) (estimate)
A hub motor is built into the wheel: the axle stays still and the outer shell, with the tyre, turns around it on bearings. Worn bearings, a loose axle or a damaged cable at the axle cause noise, wobble and drive problems. This check is done from outside, with the bike off. It does not open the motor.
Safety
- Switch the bike off and remove the key (and the swap battery if your bike has one) before spinning the wheel. A bike that goes to ready while your hand is in the wheel can injure you.
- Make sure the bike is stable on its stand.
- Do not loosen the axle nuts. On many hub motors the axle nuts and torque arms (plates that stop the axle turning in the frame) hold the motor in place; a loose axle can spin and tear the motor cable. Refitting needs the model's torque values.
You need
- A stand that lifts the motor wheel off the ground.
- A torch.
Steps
- Put the bike on the stand with the motor wheel off the ground. Switch off.
- Spin the wheel by hand slowly. A hub motor can feel slightly "notchy" or resist a little because of its magnets; this is normal on many motors. Listen for grinding, scraping or clicking.
- Spin it faster. A deep rumble or grinding that changes with wheel speed usually points to worn bearings (Letrigo).
- Hold the tyre at the top and bottom and rock it towards and away from you. Any clunk or movement points to bearing or axle wear. Compare with Check wheel bearings.
- Look at the axle nuts and torque arms: is anything loose, cracked or moved? Look for fresh shiny metal where the axle meets the frame slots; this shows the axle has been turning.
- Look at the motor cable where it leaves the axle: crushed, cut, twisted, rubbed or melted. A damaged cable here causes judder and cut-outs (em3ev).
- Check the rear brake is not dragging: Check for brake drag.
- Check for rubbing between tyre and mudguard or frame, and for stones or wire caught around the hub.
- If the wheel is very hard to turn with the bike off and the brake is free, do not ride. See Rear wheel is locked or very hard to push.
Check your work
- Wheel spins evenly with no grinding, scraping or clunk.
- No play when rocked; axle and torque arms secure; cable undamaged.
If it did not fix the problem
- Bearing noise or play: bearings in a hub motor are a workshop job. See Diagnose a motor fault.
- Axle loose or cable damaged: stop riding and take the bike to the workshop.
- Noise only under power: Grinding, clicking or growling from the motor.