Brake Rotor Thickness Variation Measurement

Brake Rotor Thickness Variation Measurement

Caution: Refer to Safety Glasses Caution (Safety Glasses Warning) in Cautions and Notices.
Caution: Refer to Vehicle Lifting Caution (Service Precautions) in Cautions and Notices.
Caution: Refer to Brake Dust Caution (Brake Dust Caution) in Cautions and Notices.
1. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle (Service and Repair) in General Information.
2. Remove the wheels assembly. Refer to Tire and Wheel Removal and Installation (Service and Repair) in Tires and Wheels.
3. Clean the friction surfaces of the brake disc with denatured alcohol, or an equivalent approved brake cleaner.




4. Using a micrometer calibrated in thousandths-of-a-millimeter, or ten-thousandths-of-an-inch, measure and record the thickness of the brake disc at 4 points, evenly spaced around the brake disc.
5. Make sure 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 brake disc, about 13 mm (1/2 in), for each measurement.
6. Calculate the difference between the highest and lowest thickness measurements recorded to obtain the amount of thickness variation.
7. Compare the thickness variation measurement to the following specification:

Brake disc maximum allowable thickness variation: 0.02 mm (0.001 in).


Important: Whenever a brake disc is refinished or replaced, the assembled lateral runout (LRO) of the brake disc must be measured to make sure optimum performance of the disc brakes.


8. If the brake disc thickness variation measurement exceeds the specification, the brake disc requires refinishing or replacement.