Drum brake

How it works

Drum brakes are still fitted to the rear of many scooters, small bikes, cruisers and classic motorcycles. The principle differs from a disc: two crescent-shaped shoes lined with friction material sit inside a drum that turns with the wheel. When you apply the brake (by cable, rod or sometimes hydraulics), a cam spreads the shoes, which rub against the inside of the drum. Springs pull them back when you release. The drum shields the linings from water and mud and wears slowly, but it sheds heat less well than a disc. As the linings wear, the control's travel increases: you take up the slack with the adjuster nut. The usual causes of poor braking are worn or glazed linings, dust built up in the drum, a sticking cable or a stiff cam. Many drum brakes have a wear indicator on the cam: when the mark goes past the allowed zone, the shoes must be replaced.

Maintenance tips

• ✓Check the wear indicator near the brake cam, if fitted, at every service.
• ✓Take up the free play with the adjuster nut without removing it all: the wheel must spin freely with the brake released.
• ✓Lubricate the control cable and the cam spindle (a little grease, never on the linings).
• ✓When replacing shoes, clean the dust from the drum with brake cleaner, without blowing it towards you.
• ✓A deeply scored or oval drum should be checked by a professional.