Brake Drum: Testing and Inspection

1. A brake drum should be visually inspected and measured with Rotunda Brake Drum Micrometer 104-00046 or equivalent. Before making an inspection or measurement, remove grease, brake fluid, and other contaminants from the brake drum using denatured alcohol.





2. Best shop practice requires measuring every brake drum with a drum micrometer regardless of visual inspection. The drum micrometer is set to the drum diameter and measures the amount and type of wear. Measure the diameter at various points 45 degrees around the circumference, and at the bottom of the deepest groove to determine if the brake drum requires replacement.

CAUTION: If the braking surface diameter has worn in excess of the maximum diameter, shown in cast figures on the outside of the brake drum, replace the brake drum. Maximum brake drum diameter (inside) is 230.1 mm (9.06 inches).