Brake Rotor Surface and Wear Inspection

Tools Required: 

• J 8001  Dial Indicator
• J 26900-1  Combimike Micrometer
• J 26900-13  Magnetic Base

1. Clean the brake pad lining contact surfaces of the brake rotor with denatured alcohol or an equivalent brake cleaner.
2. Inspect the braking surfaces of the brake rotor for the following braking surface conditions:
   • Heavy rust and/or pitting

     Light surface rust can be removed with an abrasive disc. Heavy surface rust and/or pitting must be removed by refinishing the rotor.

   • Cracks and/or heat spots
   • Excessive blueing discoloration
3. If the braking surfaces of the brake rotor exhibits one or more of the braking surface conditions, refinish or replace the brake rotor.
4. Use the J 26900-1 or an equivalent micrometer in order to measure any grooves on the rotor braking surface.
Fig 1: Using J 26900-1
Courtesy of GENERAL MOTORS CORP.
5. Compare the groove depth to the following specification:

   Specification 

   The maximum groove depth is 0.38 mm (0.015 in).

6. If the groove depth exceeds the specification, or if an excessive amount of scoring is present, refinish or replace the brake rotor.
7. Install the J 8001 and the J 26900-13 or an equivalent dial indicator and magnetic base. Position the indicator button so it contacts the brake rotor at a 90 degree angle, approximately 13 mm (0.5 in) from the rotor's outer edge.
Fig 2: Installing J 8001
Courtesy of GENERAL MOTORS CORP.
8. Measure and record the lateral runout of the brake rotor.
   1. 8.1. Rotate the rotor until the lowest reading is displayed on the indicator dial, then zero the dial.
   2. 8.2. Rotate the rotor until the highest reading is displayed on the dial.
   3. 8.3. Measure and record the amount of sealed wheel bearing play, then subtract the bearing play from the lateral runout recorded to obtain the true amount of lateral runout.
9. Compare the lateral runout of the brake rotor to the following specification:

   Specification 

   The maximum brake rotor lateral runout is 0.05 mm (0.0020 in).

10. If the brake rotor lateral runout exceeds the specification, refinish or replace the brake rotor.
11. If the brake rotor meets the qualifications for refinishing, refer to Brake Rotor Refinishing . If the brake rotor does not meet the qualifications for refinishing, replace the brake rotor. Refer to Brake Rotor Replacement .