Out-of-Round

An out-of-round drum makes accurate brake shoe adjustment impossible and is likely to cause excessive wear of other parts of brake mechanisms due to its eccentric action. An out-of-round drum can also cause severe and irregular tire wear as well as a pulsating brake pedal. When the drum exceeds the out-of-round specification limits, the drum should be refinished or replaced.

Drum roundness can be accurately measured with an inside micrometer, fitted with proper extension rods.

When measuring a drum for out-of-round, take measurements at right angles (90 degrees) to each other.