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Disc Rotor Surface & Wear Inspection

WARNING: This page is about a different car, the 2003 GMC Sonoma, 2003 GMC Jimmy, 2003 Chevrolet S10 Pickup, and 2003 Chevrolet Blazer. However, it is still accessible from the selected car via links, so may be relevant.
  1. With the tire and wheel assemblies removed and the brake rotors retained by wheel lug nuts, clean the braking surfaces of the brake rotor with denatured alcohol or an equivalent approved 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 exhibit one or more of the braking surface conditions, the rotor requires refinishing or replacement.
  4. Using a micrometer calibrated in ten-thousands of an inch, measure and record the thickness variation of the brake rotor at four or more points, around the rotor. Ensure that the measurements are only taken within the brake pad lining contact area and that the micrometer is positioned the same distance from the outside edge of the rotor for each measurement.
  5. Compare the thickness variation recorded to the Brake Rotor Maximum Allowable Thickness Variation. See DISC & DRUM BRAKE SPECIFICATIONS .
  6. If the brake rotor thickness variation exceeds the specification, the rotor requires refinishing or replacement.
  7. Using the micrometer, measure and record any grooves present on the rotor braking surface.
  8. Compare the groove or scoring depth recorded to the Brake Rotor Maximum Allowable Scoring. See DISC & DRUM BRAKE SPECIFICATIONS .
  9. If the brake rotor scoring depth exceeds the specification, or if an excessive amount of scoring is present, the rotor requires refinishing or replacement.
  10. Mount a Dial Indicator (J-8001), or equivalent and position the indicator button so it contacts the brake rotor at a 90 degree angle, approximately 0.5" (13 mm) from the rotor's outer edge.
  11. Measure and record the lateral runout of the brake rotor. Rotate the rotor until the lowest reading is displayed on the indicator dial, then zero the dial. Rotate the rotor until the highest reading is displayed on the dial. 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.
  12. Compare the lateral runout of the brake rotor to the following specification: Brake rotor maximum allowable lateral runout. See DISC & DRUM BRAKE SPECIFICATIONS .
  13. If the brake rotor lateral runout exceeds the specification, the rotor requires refinishing or replacement.
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