Brake Drum: Testing and Inspection

Maximum Drum Diameter Identification:

Measure drum runout and diameter. If not to specification, reface drum. (Runout should not exceed 0.1524 mm or 0.006 inch). The diameter variation (oval shape) of the drum braking surface must not exceed either 0.0635 mm (0.0025 inch) in 30° or 0.0889 mm (0.0035 inch) in 360°. All drums will show markings of maximum allowable diameter.