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Brake Disc Thickness Measurement

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

1. If the inboard friction surface of the brake disc is not accessible, reposition and support the calliper 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 disc with methylated spirit, or an equivalent approved brake cleaner.



3. Using a micrometer calibrated in thousandths-of-a-millimetre, or ten-thousandths-of-an-inch, measure and record the thickness of the brake disc at four or more points, evenly spaced around the disc.

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 disc, about 13 mm (½ in), for each measurement.

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