Brake Drums

INSPECTION
Any time the brake drums are removed for brake service, the braking surface diameter should be checked with a suitable brake drum micrometer at several points to determine if they are within the safe oversize limit stamped on the brake drum outer surface. If the braking surface diameter exceeds specifications, the drum must be replaced. If the braking surface diameter is within specifications, drums should be cleaned and inspected for cracks, scores, deep grooves, taper, out of round and heat spotting. If drums are cracked or heat spotted, they must be replaced. Minor scores should be removed with sandpaper. Grooves and large scores can only be removed by machining with special equipment, as long as the braking surface is within specifications stamped on brake drum outer surface. Any brake drum sufficiently out of round to cause vehicle vibration or noise while braking or showing taper should also be machined, removing only enough stock to true up the brake drum.

After a brake drum is machined, wipe the braking surface diameter with a denatured alcohol soaked cloth. If one brake drum is machined, the other should also be machined to the same diameter to maintain equal braking forces.