Checking the brake pedal

Checking and adjusting the travel of the brake pedal is crucial for proper braking. Three different pedal positions are defined to be checked: height (h), free play (a), and reserve height (r).

Adequate height (h) ensures that the primary thrust force is fully transmitted to the pedal even if half of the brake fluid leaks out of the hydraulic system. In other words, there needs to be enough height to do the braking before the pedal touches the floor. Brake pedal height is measured from the top of the pedal to the floor of the vehicle.

Measure brake pedal height

Free play (a) is the distance from the top to the resistance of the pedal push. This is actually the distance between the brake pedal connection and the master cylinder piston. The measurement is performed by lightly pressing the hand on the pedal until resistance is felt. The measured movement is the free travel of the brake pedal.

The reserve height (r) is the distance from the floor to the end position of the pressed pedal. The reserve height is required if there is air in the hydraulic system or a leak occurs, so the pedal perishes and has a higher travel required for braking.