Workshop · adjusting
Adjusting: rear wheel and chain, headlamp and mirrors
The rear wheel straight and the chain at the right tension, the headlamp at the right height and the mirrors set so you can really see something.
A rear wheel that is crooked, a headlamp that dazzles oncoming traffic or mirrors in which you only see your own shoulder: they are small things, but they make your ride a lot safer. Here is how to adjust them yourself.
Rear wheel in line and the chain at the right tension
On a chain-driven bike you set the chain tension by moving the rear wheel back or forward. You do that on both sides with chain adjusters: bolts or rotating cams. If you move one side further than the other, the rear wheel is crooked. Then chain and sprockets wear faster and the bike steers less precisely.
- Getting ready. Put the bike upright on the centre stand, in neutral. Look up in the workshop manual how much slack the chain should have.
- Loosening. Loosen the rear wheel spindle nut, and also the lock nuts of the chain adjusters. If your bike has a drum brake with a torque arm, loosen that a turn as well.
- Both sides equally. Turn the chain adjusters left and right exactly the same amount, for example half a turn each side at a time. Count the turns.
- Measuring the slack. Turn the wheel and find the tightest point of the chain. Measure the slack there, halfway along the lower run. Adjust until it matches the workshop manual.
- Checking alignment. Do not trust the marks on the swingarm blindly: they are not always accurate. Better to check using one of the methods below.
- Tightening. Push the wheel forward against the adjusters and tighten the spindle nut. Then measure the slack again; it can change when tightening. Retighten the lock nuts and the torque arm.
- Readjusting the rear brake. The rear wheel has moved, so on a rod-operated drum brake the brake adjustment and sometimes the brake light switch also change. Readjust them and check that the wheel turns freely.
Checking alignment: two methods
| Measuring from the pivot | On both sides measure the distance from the centre of the swingarm pivot to the centre of the rear spindle, with a caliper or tape measure. It must be the same left and right. |
|---|---|
| With a piece of string | Point the front wheel straight ahead. Run a string around the rear tyre, at about axle height, and pull both ends tight forward past the front wheel. The string must just touch the rear tyre on both sides, front and back. On both sides measure the distance from the string to the front tyre: it must be equal. If the front tyre is narrower than the rear, that distance is larger, but still the same left and right. |
According to Cycle World you can ignore the marks on the swingarm if the string method says the wheel is straight.
Adjusting the headlamp
- Getting ready. Put the bike on level ground, on both wheels (not on the stand), with the tyres at the right pressure. Have someone sit on the bike in riding position, or sit on it yourself. Then the bike sits as it does when riding.
- In front of a wall. Place the bike straight in front of a light-coloured wall or garage door, a few metres away, with the front wheel straight.
- Marking the height. Measure the height of the centre of the headlamp from the ground and put a cross on the wall at the same height, straight in front of the headlamp.
- Dipped beam on. The bright part of the beam must fall just below the cross, and not veer to the left or right. Exactly how much lower is in the workshop manual.
- Adjusting. On many classics you turn the whole headlamp in its brackets: loosen the two bolts at the side, tilt the lamp and tighten them again. Others have a small adjusting screw in the rim of the headlamp.
- Checking. Check that it is also right on main beam, and ride a short way in the dark. Do you dazzle oncoming traffic? Then a little lower.
Adjusting the mirrors
- In riding position. Sit on the bike as you ride, with your hands on the bars.
- Shoulder just in view. Set each mirror so that on the inside you can just see a little of your own arm or shoulder. Then you know where you are.
- Horizon in the middle. The road behind you should be roughly in the middle of the mirror, not the sky or the tarmac.
- Tightening. Tighten the mirrors so that the wind or vibration does not turn them. Do they vibrate a lot? Check whether the mounting is loose.
- Blind spot. Even with good mirrors there is still a blind spot. Always look over your shoulder before changing lanes.
After adjusting
- Take a short test ride and check that everything is tight.
- Check the chain tension again after the first few hundred kilometres.
- See also Safely on the road for tyres, chain and lubrication.