Conditions and Causes

FIGURE 1 - HOLE WHEEL NUT TIGHTENING SEQUENCE:

CONDITION

Some vehicles may exhibit a pulsating or vibrating condition (roughness) when the brakes are applied. This bulletin specifically addresses pulsation resulting from disc brake rotor thickness variation. It should be recognized that vibration perceived by the customer may be induced by rear brakes or may also be due to vibration from other components such as drivetrain, tires, and/or road surface conditions.

CAUSES

One possible cause of rear drum brake pulsation is an out-of-round condition (radial run out) in a rear drum. This may occur during manufacture, however, a brake drum may also be distorted if pried off, struck with a hammer, or dropped during routine brake inspection or service.

Causes of rear brake pulsation on vehicles equipped with four-wheel disc brakes are essentially the same as those described for front brake pulsation.