Common Problems After an E-Bike Conversion

Most problems after a conversion come as no surprise: axle, spokes, connectors, sensor, chain. Here is what typically causes them and what you can do. Most points are experience, not officially verified.

Overview

Now line by line.

Axle spins in the dropout

This is the most dangerous case. A hub motor produces torque at the axle. Without a torque arm, the flattened axle can turn in the dropout and, in the worst case, work its way out. The wheel can come loose, and that does not happen quietly. With aluminium dropouts and front motors an arm is always right. Details under torque arm. Tighten the axle nuts with a torque wrench and check them after the first rides.

Spokes break

The motor makes the wheel heavier, and the spokes have to transmit more force. Thin spokes often do not last long under that. Stronger spokes are better. Re-tension the spokes after about 100 km, because freshly built wheels settle. A wheel that was already weak before is no exception. If you are replacing wear parts anyway, think of the wheels, see frame and weight.

Motor cuts out

This likes to happen in rain, especially at the connectors. Water in a connector causes contact resistance or a short. The connectors (Higo, Julet) are the most common source of faults in the whole kit. Proceed like this:

1. Disconnect the connector and let it dry.
2. Clean the contacts, for example with contact spray.
3. Rub in a little grease so that no water gets in.
4. Route the cable so that water does not collect near the connector. A small drip loop helps.
5. Secure it neatly with spiral sleeving and cable ties so nothing chafes.

More on the components in the glossary.

Jerky when pulling away

With a cadence sensor, assist feels more like being pushed. That comes with the design and is not a defect. Check:

• The gap between sensor disc and sensor, usually only a few millimetres
• Settings in the display or controller, such as the start-up level
• Whether the sensor works cleanly with the magnet

If you do not like the jerkiness, look at a kit with a torque sensor, even though it costs more.

Chain wears quickly

This mainly affects mid-drives. The chain carries the motor's force too, and shifting under load adds to the strain. Ease off briefly when shifting and keep pedalling lightly. Check the chain regularly and replace it before it takes the cassette and chainring with it. More on comparing the types under mid-drive vs hub motor.

Range too low

Manufacturer figures are mostly ideal values; in practice often only about 70 % counts (GIGA). Cold, headwind, terrain and weight subtract more. Plan with the lower end of the range and use realistic values in the range calculator. Details under battery.

Workshop refuses

Some workshops will not service or repair converted bikes because the conversion counts as a modification of the manufacturer's product (Fahrrad XXL). Ask before converting whether your workshop will stay on board. If not, find one that takes converted bikes. That saves frustration when something jams later.

When nothing works at all

If the motor will not start despite connectors, sensor and battery being fine, narrow it down: measure the battery with a multimeter, check the display, unplug connections one by one and reconnect them. If you find no fault, contact the dealer. That is why a dealer in the EU who offers support is worth it. What that means for the budget is under costs.

Does a conversion fit your bike?

How reliable is this?

The statements on range and on workshops that refuse conversions come from the linked sources. Causes and fixes for the other problems are experience and assumptions that Fabio is still checking.