- Clean the brake shoe lining contact surface
of the brake drum with denatured alcohol or an equivalent brake cleaner.
- Using a brake drum micrometer calibrated in thousands of an inch, measure
and record the largest diameter of the brake drum at four or more points, equally
spaced around the drum.
Ensure that the measurements are only taken within the brake shoe lining contact
area and that the micrometer is positioned the same distance from the outside edge
of the drum for each measurement.
- Compare the largest diameter measurement recorded to the following specifications:
Specification
• | Brake drum maximum allowable diameter after resurfacing 230.65 mm
(9.08 in). |
• | Brake drum discard diameter 231.0 mm (9.09 in). |
- If the largest diameter measurement of the brake drum is less than the
maximum allowable diameter after resurfacing specification; the drum may be able
to be resurfaced, depending upon surface and wear conditions which may be present.
- If the largest diameter measurement of the brake drum is equal to or
greater than the maximum allowable diameter after resurfacing specification; the
drum may not be resurfaced.
- If the largest diameter measurement of the brake drum is equal to or
greater than the discard diameter specification; the drum requires replacement.