A wheel and tyre are never exactly the same weight all round. A heavy spot makes the wheel shake at certain speeds, usually felt in the handlebars or footpegs. Balancing adds small weights opposite the heavy spot. It is done after fitting a new tyre and whenever vibration appears at a steady speed.
Safety
- A heavy, badly balanced front wheel can start a wobble at speed. Slow down if the bars shake.
- Balance weights must be fixed firmly. A weight that flies off can hit someone.
Check first (at home)
- Check pressure, tyre condition and wheel bearings: Check tyre pressure, Inspect tyres, Check wheel bearings.
- Check runout: Check a wheel for runout. Balancing cannot fix a bent rim.
- Check that the paint dot on the tyre (the light spot) lines up with the valve. If not, the tyre may have been fitted without care.
- Look for lost weights: clean marks or glue patches on the rim.
A rough check on the bike rarely works well, because brake pads, seals, the chain and the speedo drive stop the wheel turning freely. Proper balancing is done with the wheel off the bike.
What the workshop should do
- Remove the wheel, remove old weights and clean the rim.
- Mount the wheel on a balancing stand or machine on its own bearings or on a balancing axle.
- Static method: let the wheel turn freely and stop. The heavy spot settles at the bottom. Add weight at the top until the wheel stays still in any position.
- Dynamic machine: spin the wheel and follow the readout for where and how much weight to add.
- Fix weights: stick-on weights on the clean flat inner rim of cast wheels, clamp weights on spokes for spoked wheels.
- Refit the wheel, tighten the axle to the bike's value, check the brake.
What to ask for
- Old weights removed, not just more weight added.
- Weights placed away from the brake disc and caliper path.
If it did not fix the problem
- Still vibrates: Vibration at certain speeds.