GM Service Manual Online
For 1990-2009 cars only

Brake Rotor Thickness Measurement J56

Caution: Refer to Brake Dust Caution in the Preface section.

  1. If the inboard friction surface of the brake rotor is not accessible, reposition and support the caliper with the brake pads. Refer to Front Disc Brake Pads Replacement and/or Rear Disc Brake Pads Replacement .
  2. Clean the friction surfaces of the brake rotor with denatured alcohol, or an equivalent approved brake cleaner.

  3. Object Number: 693340  Size: SH
  4. Using a micrometer calibrated in thousanths-of-a-millimeter, or ten-thousanths-of-an-inch, measure and record the thickness of the brake rotor at four or more points, evenly spaced around the rotor.
  5. 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.

  6. Compare the lowest thickness measurement recorded to specifications. Refer to Disc Brake Component Specifications .
  7. If the lowest thickness measurement of the brake rotor is above the minimum allowable thickness after refinishing specification, the rotor may be able to be refinished, depending upon surface and wear conditions which may be present.
  8. If the lowest thickness measurement of the brake rotor is at or below the minimum allowable thickness after refinishing specification, the rotor may not be refinished.
  9. If the lowest thickness measurement of the brake rotor is at or below the discard thickness specification, the rotor requires replacement.

Brake Rotor Thickness Measurement JE5, JL9

Caution: Refer to Brake Dust Caution in the Preface section.

  1. If the inboard friction surface of the brake rotor is not accessible, reposition and support the caliper with the brake pads. Refer to Front Disc Brake Pads Replacement and/or Rear Disc Brake Pads Replacement .
  2. Clean the friction surfaces of the brake rotor with denatured alcohol, or an equivalent approved brake cleaner.

  3. Object Number: 693340  Size: SH
  4. Using a micrometer calibrated in thousanths-of-a-millimeter, or ten-thousanths-of-an-inch, measure and record the thickness of the brake rotor at four or more points, evenly spaced around the rotor.
  5. 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.

  6. Compare the lowest thickness measurement recorded to specifications. Refer to Disc Brake Component Specifications.
  7. If the lowest thickness measurement of the brake rotor is above the minimum thickness specification, the rotor may be able to be refinished, depending upon surface and wear conditions which may be present.
  8. If the lowest thickness measurement of the brake rotor is below the minimum thickness specification, the rotor may not be refinished.
  9. If the lowest thickness measurement of the brake rotor is below the minimum thickness specification, the rotor requires replacement.