Brake Rotor Inspecting and Machining

In manufacturing the brake rotor, tolerances of the braking surfaces for flatness, parallelism, and lateral runout are held very close. The maintenance of close tolerances on the shape of the braking surfaces is necessary to prevent brake roughness and brake noise.
In addition to these tolerances, the surface finish must be held to a specified range. The control of the braking surface finish is necessary to avoid pulls and erratic performance and to extend lining life.
When performing routine brake maintenance, rotors should not be refinished, unless there is a brake pulsation caused by the rotors or the rotors are excessively scored.
Scoring of the rotor surfaces not exceeding 1.5 mm (0.060 inch) in depth, which may result from normal use, is not detrimental to brake operation.

THICKNESS VARIATION CHECK





Thickness variation can be checked by measuring the thickness of the rotor at four or more points around the circumference of the rotor. All measurements must be made at the same distance in from the edge of the rotor. Use a micrometer graduated in ten-thousandths of an inch (0.002 mm).
A rotor that varies in thickness by more than 0.013 mm (0.0005 inch) can cause pedal pulsation and/or front end vibration during brake applications. A rotor that does not meet these specifications should be refinished to specifications or replaced.

LATERAL RUNOUT CHECK
1. Remove road wheel and install two wheel nuts 180 degrees apart to retain rotor.
2. Fasten a dial indicator graduated in ten-thousandths of an inch (0.0001 in. [0.002 mm]) to the steering knuckle so that the indictor stylus contacts the rotor about 10 mm (0.40 inch) from the rotor edge.
3. Zero the dial indicator.





4. Move the rotor one complete revolution and observe total indicated runout (TIR).
Maximum Combined Hub, Bearing, and Rotor
Lateral Runout: 0.060 mm (0.0024 inch)
Lateral runout of the rotor, if excessive, can often be improved by cleaning dirt and rust from hub and rotor mating surfaces, and/or indexing the rotor on the hub one or two bolt positions from the original position. If the lateral runout cannot be corrected by indexing the rotor, check the hub and bearing assembly for excessive lateral runout. If the hub and bearing assembly lateral runout exceeds 0.040 mm (0.0016 inch), replace the hub and bearing assembly. If lateral hub and bearing runout is within specifications, refinish or replace the rotor as necessary. If installing a new rotor, inspect the inside hub mating surface. Runs in the paint should be sanded off prior to installing a new rotor.