Brake Rotor/Disc: Testing and Inspection
CAUTION: Disc brakes must be kept within the allowable service values in order to maintain normal brake operation.
Before turning the brake disc, the following conditions should be checked.
FRONT DISC BRAKE RUN-OUT CHECK AND CORRECTION
1. Remove the caliper support; then raise the caliper assembly upward and secure it 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: 0.06 mm (0.002 inch)
4. If the run-out of the brake disc is limit value or more, turn rotor with an on-car type brake lathe ("Accuturn-8750" or equivalent). If it still exceeds the limit, inspect hub end play.
Limit: 0.05 mm (0.002 inch)
5. If the play exceeds the limit, check the hub. If the play does not exceed the limit, replace the brake disc.
REAR DISC BRAKE RUN-OUT CHECK AND CORRECTION
1. Remove the caliper support; then raise the caliper assembly upward and secure it with a wire.
2. Check 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 (0.003 inch)
4. If the runout of the brake disc is the limit value or more, change the phase of the disc and hub, and then measure the run-out again.
1. Before removing the brake disc, place a mating mark on both the wheel stud and disc with chalk where the run-out is greatest.
2. Place a dial gauge as shown in the illustration, and then move the hub in the axial direction and measure the play.
Limit: 0.05 mm (0.002 inch)
3. If the play does not exceed the limit install the brake disc at a different phase, and then check the run-out of the brake disc again.
5. If the run-out cannot be corrected by changing the phase of the brake disc, replace the disc.
BRAKE DISC THICKNESS CHECK
1. Remove dirt and rust from the brake disc surface.
2. Using a micrometer, measure disc thickness at eight positions, approximately 45 degrees apart and 10 mm (0.4 inch) in from the outer edge of the disc.
Standard value: 24.0 mm (0.9 inch)
Minimum limit: 22.4 mm (0.88 inch)
NOTE: Thickness variation (at least 8 positions) should not be
more than 0.015 mm (0.0006 inch).
3. If the disc thickness is less than 22.4 mm (0.88 inch) thick, replace it with a new one. If thickness variation exceeds the specification, turn rotor with an on-the-car type brake lathe ("Accuturn-8750" or equivalent).
If the calculated final thickness after turning the rotor is less than the standard value, replace the disc.
1. Remove dirt and rust from the brake disc surface.
2. Measure the disc thickness at four positions or more.
Standard value: 10.0 mm (0.4 inch)
Minimum limit: 8.4 mm (0.33 inch)
3. Thickness variations (at least 4 positions) should not be more than 0.015 mm (0.0006 inch).
4. If the disc is thickness than 8.4 mm (0.33 inch) thick, replace it with a new one. If thickness variation exceeds the specification, turn rotor with an on,-the-car brake lathe ("Accuturn-8750" or equivalent).
If the calculated final thickness is less than the standard value, replace the disc.
BRAKE LINING THICKNESS CHECK
CAUTION:
- Whenever the shoe and lining assembly is replaced, replace both RH and LH assemblies as a set to prevent the car from pulling to one side when braking.
- If there is a significant difference in the thickness of the shoe and lining assemblies on the left and right sides, check the sliding condition of the piston.
NOTE: For brake lining thickness for drum-in-disc brake, refer
to Specifications in Parking Brake System.
Specifications
1. Remove the brake drum.
2. Measure the thickness of the brake lining at the area with the worst wear.
Standard value: 4.9 mm (0.19 inch)
Minimum limit: 1.0 mm (0.04 inch)
3. Replace the shoe and lining assembly if the brake lining thickness is less than the limit or if it is not worn evenly.