Home mechanic (basic tools) ยท Time: 20 to 40 min (estimate) (estimate)
On many older and low-cost bikes a spinning inner cable drives the speedometer from a small gearbox at the front wheel hub (sometimes from the gearbox output). A broken or dry cable makes the needle stop, flicker or whine. Many newer bikes use an electronic speed sensor instead and have no cable: for those see Check the speed sensor.
Safety
- Lift the front wheel only with the bike stable.
- Ride without a working speedometer only with care: many places require one by law.
You need
- A new cable of the correct length and end type (square or slotted drive ends, knurled or clipped fittings).
- Light grease, cable ties.
Steps: find the fault first
- Unscrew the cable at the instrument end and pull it free.
- Lift the front wheel and turn it forward slowly. Watch the inner cable tip at the top.
- Inner turns: the cable and hub drive are fine. The fault is in the instrument (Speedometer or odometer does not work).
- Inner does not turn: pull the inner cable out from the top. If it comes out in two pieces, the inner has snapped: replace the cable.
- Inner is whole but does not turn: disconnect the bottom end at the hub and turn the wheel. Watch the drive slot in the hub gearbox. No movement means the hub drive gear or its tangs are broken or not engaged with the hub (check when the wheel was last removed).
Steps: replace
- Note the route: through which guides, on which side of the fork and headlight.
- Disconnect both ends. Remove the old cable.
- Grease the inner cable lightly along its length, but keep the top part near the instrument clean so grease does not creep into the speedometer.
- Fit the bottom end to the hub drive first, turning the wheel slightly so the square or slot engages. Tighten the fitting by hand or with pliers gently.
- Route the cable along the old path: no tight bends, clear of the steering stops, not pulled when the bars turn.
- Fit the top end to the instrument, engage the drive, tighten the ring.
- Secure with cable ties, never to the brake hose.
Check your work
- Needle moves smoothly from low speed, no flicker or noise.
- Turn bars lock to lock: the cable is not pulled tight or kinked.
If it did not fix the problem
- Needle still dead with a turning cable: instrument fault, see Speedometer or odometer does not work.
- Hub drive damaged: fit a new hub drive and check its tangs sit in the hub slots before tightening the axle (Remove and refit the front wheel).