Document rxD60L1VwaDMwoYJ17nonwJva

LESSON ONE-MODULE 2 Rotor Runout BRAKE SYSTEM SERVICE Checking Runout Item Description 1 Checking Wheel Hub Runout Item Description 2 Checking Rotor Runout Rotor runout is the amount of side to side movement (wobble) measured near the outer friction surface of the rotor. Runout is caused by warping and twisting of the rotor due to the heat generated during braking. Excessive runout is often indicated by brake pedal pulsation. Before checking rotor runout you must ensure that all play is removed from the wheel bearing. If rotor runout is excessive, and the vehicle has "top hat" type rotor, which mounts over the lug bolts of the wheel hub, the hub runout must be checked after surface cleaning. Prior to checking rotor runout ensure that all brake pad drag has been eliminated by pushing the caliper piston slightly into its bore (or remove the caliper assembly). Rotor runout is measured using a dial indicator. Mount the dial indicator to a fixed surface, and position the plunger at the outer friction surface of the rotor. Turn the rotor one complete turn. Any runout will cause the dial indicator pointer to move. Any runout that is greater than the specification in the vehicle service manual will require machining or replace ment of the rotor. 40 September, 2005 Brake System Diagnosis and Repair