Brake Drum: Testing and Inspection

- Minor scores on a brake drum can be removed with sandpaper. Do not refinish brake drums to remove score marks.
- A brake drum surface which is highly polished can cause the brake to lock up. This polished condition should be removed either with sandpaper or by refinishing the brake drum.
- A brake drum that is out of round sufficiently enough to cause vehicle vibration or noise when braking should be refinished. Remove only enough stock to true-up the brake drum.

Using Brake Drum Micrometer:

- Use a brake drum micrometer to measure the braking surface diameter. If it has worn more than the maximum diameter, shown on the outside of the brake drum, the brake drum must be replaced.
- If new rear brake shoes and linings are being installed, resurface the brake drums to remove glazing and to ensure an equal friction surface from side-to-side. Resurfacing will also correct out-of-round and bell conditions.