- 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 (JB6)
• | Brake drum maximum allowable diameter after refinishing 284.73 mm
(11.21 in).
|
• | Brake drum discard diameter 285.50 mm (11.24 in).
|
Specification (JD7)
• | Brake drum maximum allowable diameter after refinishing 331.72 mm
(13.06 in).
|
• | Brake drum discard diameter 332.49 mm (13.09 in).
|
Specification (JB8)
• | Brake drum maximum allowable diameter after refinishing 331.72 mm
(13.06 in).
|
• | Brake drum discard diameter 332.49 mm (13.09 in).
|
- If the largest diameter measurement of the brake drum is less
than the maximum allowable diameter after refinishing specification; the drum
may be able to be refinished, 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 refinishing specification;
the drum may not be refinished.
- If the largest diameter measurement of the brake drum is equal
to or greater than the discard diameter specification; the drum requires replacement.