Out-of-Round or Tapered

An out-of-round or tapered drum prevents accurate brake shoe adjustment and is likely to cause excessive brake shoe adjustment and is likely to cause excessive wear of other brake parts due to its eccentric action. An out-of-round drum can also cause severe and irregular tire tread wear as well as a pulsating brake pedal. When the drum exceeds the specification limits in taper and/or out-of-round, refinish the drum to true up the braking surface. Out-of-round and taper can be accurately measured with an inside micrometer and extension rods.
When measuring a drum for out-of-round and taper, take measurements at the open and closed edges of the machined surface and at right angles to each other.