Brake Drum

DIAGNOSIS AND TESTING - BRAKE DRUM
With the drum off the vehicle, measure the drum for diameter variation (oval shape). The diameter variation of the drum braking surface must not exceed specifications listed in the following table.

Measure brake drum runout. Brake drum runout should be checked with the drum mounted on a brake lathe. Brake drum runout should not exceed specifications listed in the following table.

If either of these measurements are not within specification, reface or replace the drum.





BRAKE DRUM LIMITS

Always replace the drum if machining will cause the diameter to exceed drum maximum diameter. All brake drums are marked with the maximum allowable brake drum diameter (Fig. 63). Maximum brake drum diameter can also be found in the following table.