Brake Rotor Thickness Measurement

Tools Required 

J 26900-1  Combimike Micrometer. See Special Tools .

1. Reposition and support the caliper and the brake pads. Refer to Brake Pads Replacement - Front  or to Brake Pads Replacement - Rear  as applicable.
2. Clean the brake pad lining contact surfaces of the brake rotor with denatured alcohol or an equivalent brake cleaner.
Fig 1: Measuring Brake Rotor Thickness
Courtesy of GENERAL MOTORS CORP.
3. Use the J 26900-1  , or the equivalent micrometer, in order to measure the thickness of the brake rotor. See Special Tools . Measure the thickness of the rotor at 4 or more points equally spaced around the rotor. Position the J 26900-1  , or the equivalent, at the same distance from the outside edge of the rotor, in the brake pad lining contact area. See Special Tools .
4. Compare the measurements to the following specifications:

   Specifications: 

   • The discard specification for the front brake rotor is 30.0 mm (1.181 in).
   • The discard specification for the rear brake rotor is 16.0 mm (0.630 in).

5. If the smallest measurement exceeds the discard specification, you may be able to resurface the brake rotor, depending upon the thickness variation and the surface condition. Refer to Brake Rotor Thickness Variation Measurement  and to Brake Rotor Surface and Wear Inspection .
6. If the smallest measurement is equal to or less than the discard specification, replace the brake rotor. Refer to Brake Rotor Replacement - Front  or to Brake Rotor Replacement - Rear  as applicable.