Brake Rotor/Disc: Testing and Inspection
CAUTION: To maintain safe braking performance, the disc brake rotors must be kept within allowable service specifications.
Before re-finishing or re-processing the brake disc surface, the following conditions should be checked.
BRAKE DISC RUN-OUT CHECK AND CORRECTION
1. Remove the caliper support bolts, then raise the caliper assembly upward and secure with a wire.
2. Inspect the disc surface for grooves, cracks, and rust. Clean the disc thoroughly and remove all rust.
3. Place a dial gauge approximately 5 mm (0.2 inch) from the outer circumference of the brake disc, and measure the runout of the disc.
Limit: 0.08 mm (0.0031 inch)
NOTE: Tighten the nuts in order to secure the disc to the hub.
4. If the run-out of the brake disc is equivalent to or exceeds the limit specification, change the phase of the disc and hub, and then measure the run-out again.
1. Before removing the brake disc, chalk both sides of the wheel stud on the side at which run-out is greatest.
2. Remove the brake disc, and then place a dial gauge as shown; then move the hub in the axial direction and measure the play.
Limit: 0.05 mm (0.0020 inch)
If the play is equivalent to or exceeds the limit, disassemble the hub knuckle and check each part.
3. If the play does not exceed the limit specification, install the brake disc at a position 180° away from the chalk mark, and then check the run-out of the brake disc once again.
5. If the run-out cannot be corrected by changing the phase of the brake disc, replace the brake disc or turn rotor with an on the car type brake lathe ("Accuturn-8750" or equivalent). Be sure to follow the exact brake lathe manufacturer instructions. Rotors turned on the vehicle will often have a lower run-out than a new brake disc.
BRAKE DISC THICKNESS CHECK
1. Using a micrometer, measure disc thickness at eight positions, approximately 45° apart and 10 mm (0.39 inch) in from the outer edge of the disc.
Brake disc thickness
Standard value:
Limit:
Thickness variation (at least 8 positions)
The difference between any thickness measurements should not be more than 0.015 mm (0.0006 inch).
2. If the disc is beyond the limits for thickness, remove it and install a new one. If thickness variation exceeds the specification, replace the brake disc or turn rotor with an on the car type brake lathe ("Accuturn - 8750" or equivalent). Be sure to follow the exact brake lathe manufacturer instructions.