Brake Rotor Thickness Variation Measurement JL9, J55, J56
Warning: Refer to Brake Dust Warning in the Preface section.
Note: Any disc brake rotor that exhibits thickness variation exceeding the maximum acceptable level must be refinished or replaced. Thickness variation exceeding the maximum acceptable level can cause brake pulsation.
- If the inboard friction surface of the brake rotor is not accessible, reposition and support the caliper with the brake pads. Refer to Front Brake Caliper Replacement and/or Rear Brake Caliper Replacement.
- Clean the friction surfaces of the brake rotor with denatured alcohol, or an equivalent approved brake cleaner.
- Using a micrometer calibrated in thousandths-of-a-millimeter, or ten-thousandths-of-an-inch, measure and record the thickness of the brake rotor at 4 or more points, evenly spaced around the rotor.
- Calculate the difference between the highest and lowest thickness measurements recorded to obtain the amount of thickness variation.
- Compare the thickness variation measurement to the following specification:
- If the brake rotor thickness variation measurement exceeds the specification, the rotor requires refinishing or replacement.
Ensure that the measurements are only taken within the friction surfaces and that the micrometer is positioned the same distance from the outer edge of the rotor, about 13 mm (½ in), for each measurement.
Specification
Brake rotor maximum allowable thickness variation: 0.025 mm (0.001 in)
Note: Whenever a brake rotor is refinished or replaced, the assembled lateral runout (LRO) of the rotor must be measured to ensure optimum performance of the disc brakes.
Brake Rotor Thickness Variation Measurement J57
Warning: Refer to Brake Dust Warning in the Preface section.
Note: Any disc brake rotor that exhibits thickness variation exceeding the maximum acceptable level must be replaced. Thickness variation exceeding the maximum acceptable level can cause brake pulsation.
- If the inboard friction surface of the brake rotor is not accessible, reposition and support the caliper with the brake pads. Refer to Front Brake Caliper Replacement and/or Rear Brake Caliper Replacement.
- Clean the friction surfaces of the brake rotor with soap and water or denatured alcohol.
- Using a micrometer calibrated in thousandths-of-a-millimeter, or ten-thousandths-of-an-inch, measure and record the thickness of the brake rotor at 4 or more points, evenly spaced around the rotor.
- Calculate the difference between the highest and lowest thickness measurements recorded to obtain the amount of thickness variation.
- Compare the thickness variation measurement to the following specification:
- If the brake rotor thickness variation measurement exceeds the specification, the rotor requires replacement.
- Perform the Brake Rotor Surface and Wear Inspection.
Note: Do not clean the friction surfaces of the brake rotor with chemical brake cleaners.
Allow the friction surfaces of the brake rotor to thoroughly air dry.
Ensure that the measurements are only taken within the friction surfaces and that the micrometer is positioned the same distance from the outer edge of the rotor, about 13 mm (½ in), for each measurement.
Specification
Brake rotor maximum allowable thickness variation 0.02 mm (0.0008 in)
Note: Whenever a brake rotor is replaced, the assembled lateral runout (LRO) of the rotor must be measured to ensure optimum performance of the disc brakes.
