Adjust the rear brake pedal

Home mechanic (basic tools) · Time: 15 to 30 min (editorial estimate) (estimate)

The rear brake pedal has two settings: its height (where the pedal rests under your foot, set by a stop bolt) and its free play (how far it moves before the brake starts to work). On a drum brake, free play is set at the rod or cable. On a hydraulic (disc) rear brake, the pedal pushes a rod into the rear master cylinder; that rod must leave the piston free. This page covers both.

Safety

• A pushrod set too long holds the master cylinder piston in. The brake then drags, gets hot and can lock the wheel. On a combined braking (CBS) bike it can also make the front brake drag.
• Always test the brake at walking speed after adjusting.
• If the pedal pivot is stiff or rusted, service it first (Service footpegs and foot pedals), or the adjustment will not hold.

You need

• Your bike's pedal free play value. K-Light 125: 20 to 30 mm. Other bikes: use the manual.

Steps

1. Put the bike on its centre stand. Sit on it if you want to set the pedal height to suit your boot.
2. Pedal height: loosen the stop bolt locknut, turn the stop bolt until the pedal rests where your foot can reach it without lifting the leg, then tighten the locknut. Changing height changes free play, so always do free play next.
3. Drum brake free play: set it at the wing nut on the brake rod as in Adjust a drum brake.
4. Hydraulic rear brake: find the pushrod between the pedal and the rear master cylinder. Loosen its locknut.
5. Turn the pushrod (or its adjuster) until there is a very small gap between the rod and the master cylinder piston, with no pressure on the piston. K-Light 125: 0 to 0.2 mm, and the piston must be completely free. Turning the adjuster in reduces free play; turning it out increases it.
6. Measure free play at the pedal pad: press the pedal by hand until you feel the brake start to work. K-Light 125: 20 to 30 mm.
7. Tighten the locknut while holding the rod still.
8. Lift the rear wheel and spin it. It must not drag. On a CBS bike also spin the front wheel while someone presses the pedal lightly and releases it: both brakes must release fully.
9. Check the brake light comes on just as the brake starts to work: Test and adjust the brake light switches.

Check your work

• Pedal rests at a comfortable height and returns fully on its spring.
• Free play is within the manual range.
• Both wheels spin freely after you release the pedal.
• Brake light works.

If it did not fix the problem

• Pedal still travels too far on a hydraulic brake: air or a worn master cylinder. See Rear brake pedal travels too far.
• Pedal heavy or slow to return: Foot pedal or footpeg is stiff, bent or loose.
• CBS bike brakes the front too much or not at all: Combined braking (CBS) does not work as it should.

Reference values (K-Light 125)