Cause of Vibration/Pulsation Problems

2) CAUSE OF VIBRATION/PULSATION PROBLEMS

Figure 3:

Brake rotor thickness variation causes brake vibration due to changes in the braking force as thick/thin portions of the rotor pass the pads. Brake rotor thickness variation can be measured with a micrometer as shown in Figure 3.

There are two factors which cause excessive rotor thickness variation:

A. ROTOR RUN-OUT

- Rotor run-out can be caused by poor mating of flanges between the hub and rotor when assembled as a unit. Manufacturing tolerance stack-up of the rotor and hub may also cause excessive rotor assembly run-out (see Figure 4 below).

Figure 4:

- If there is rotor run-out, a portion of the rotor comes into contact with the brake pad on each rotor revolution. If left like this, the portion of the rotor that contacts the brake pad becomes worn, creating thickness variation.

B. EXCESSIVE RUST OR CORROSION ON ROTOR SURFACE

- Driving in areas where salt is applied to road surfaces for winter conditions can cause rust and corrosion when the vehicle is parked for an extended period of time. This occurs on the area where the brake pads are not in contact with the rotor.

- When a vehicle is driven with rusted rotors, the area with corrosion wears at a different rate than the non-corroded areas, resulting in excessive thickness variation.