After a long hill, a heavy load or a hot day, the motor is too hot to touch, a temperature warning appears, or power drops until the bike rests. Hub motors can build heat faster than they can lose it on steep, slow climbs with a heavy load (Upway). Most bikes protect the motor by reducing power, so the drop is a warning, not the fault itself. The goal is to find what is adding load or blocking cooling, and to check for an electrical fault that makes extra heat.
Is it safe to ride?
Ride with care. Stop in a safe place, let the motor cool, then continue gently. Stop riding if you smell burning: a sharp burning smell can mean overheated winding insulation (Letrigo).
Quick checks first
- Load: passenger plus cargo on steep hills?
- Tyre pressure low?
- Brake dragging (wheel hot near the brake)?
- Riding at full throttle at low speed up long hills?
- Motor covered in packed mud?
Diagnose it step by step
1Is there a burning smell or smoke?
- Yes: stop, switch off, let cool, do not ride. Workshop: Diagnose a motor fault.
- No: go to step 2.
2. Is the brake dragging? Check for brake drag.
- Yes: fix the brake. A dragging brake makes the motor work hard and heats the hub.
- No: go to step 3.
3. Are the tyres soft? Check tyre pressure.
- Yes: pump to the correct pressure.
- No: go to step 4.
4Is the load or the route much harder than normal (heavy cargo, passenger, long steep climbs, very hot weather)?
- Yes: this may be normal protection. Reduce load, use a lower power mode on long climbs, rest in shade. Check cooling of the motor and controller.
- No, it happens on your normal route: go to step 5.
5. Is the controller also hot, or is there a code? Read electric drive error codes.
- Controller hot: see Controller overheats or shuts down.
- Code or judder: a phase or Hall fault makes the motor work out of step and heat up. Check motor phase connectors.
- No: go to step 6.
6Did the problem start recently with no change in use?
- Yes: workshop: Diagnose a motor fault. Letrigo notes a winding imbalance can cause weak power and overheating.
Causes, most likely first
| Cause | How to confirm | Fix |
|---|---|---|
| Heavy load on long climbs | Only on hills with load | Lower mode, less load, rest |
| Brake dragging | Hub and brake hot | Check for brake drag |
| Low tyre pressure | Gauge | Check tyre pressure |
| Blocked cooling, mud packed | Visible | Check cooling of the motor and controller |
| Phase connector or Hall fault | Code, judder | Check motor phase connectors |
| Winding fault | Workshop test | Diagnose a motor fault |