Brake pedal vibration

1. When applying the brakes, a pulsating force tries to push the brake pad back. The pulsation is transmitted to the brake pedal.
2. The following are the main possible causes of brake judder:

Due to an excessive runout (side-to-side wobble) of the disc plate, the thickness of the disc plate is uneven.

1. If the runout is more than 0.1 mm {0.004 in} at the position 10 mm {0.39 in} from the disc plate edge, uneven wear occurs on the disc plate because the pad contacts the plate unevenly.
2. If the runout is less than 0.1 mm {0.004 in}, uneven wear does not occur.

The disc plate is deformed by heat. 

1. Repeated panic braking may raise the temperature in some portions of the disc plate by approx. 600°C {1, 112°F}. This results in a deformed disc plate.

Due to corrosion, the thickness and friction coefficient of the disc plate change. 

1. If the vehicle is parked in damp conditions for a long time, corrosion occurs on the friction surface of the disc plate.
2. The thickness of corrosion is uneven and sometimes appears like a wave pattern, which changes the friction coefficient and causes a reaction force.