For 1990-2009 cars

1. Clean the brake shoe lining contact surface of the brake drum with GM Brake Parts Cleaner, GM P/N 12346139, or an equivalent brake cleaner.
2. Use a brake drum micrometer calibrated in thousands of an inch in order to measure the largest diameter of the brake drum. Measure the diameter of the brake drum at four or more points equally spaced around the drum.

Measure the diameter of the brake drum in the brake shoe lining contact area.

Position the micrometer the same distance from the outside edge of the drum.

3. Compare the largest diameter measurement to the following specifications:

Specification

• | The maximum brake drum diameter after resurfacing is 201.0 mm (7.913 in).

• | The brake drum discard diameter is 202.0 mm (7.953 in).

4. If the largest diameter measurement of the brake drum is less than the maximum allowable diameter after resurfacing specification; you may be able to resurface the drum, depending upon surface and wear conditions which may be present. Refer to Brake Drum Surface and Wear Inspection .
5. If the largest diameter measurement of the brake drum is equal to or greater than the maximum brake drum diameter after resurfacing specification, do not resurface the drum.
6. If the largest diameter measurement of the brake drum is equal to or greater than the discard diameter specification, replace the drum. Refer to Brake Drum Replacement .