How do you measure the diameter of a brake drum?

How to Measure Drum Brakes

1. Remove the drum from the wheel employing a drum puller if necessary.
2. Inspect the outer facing of the rotor and locate the stamped maximum diameter or machine-to diameter in the cast.
3. Place the drum face down onto a flat surface so the interior diameter of the drum is facing upward.

What tool is used to measure the diameter of a brake drum?

The digital ATE brake drum caliper gauge is an indispensable instrument for precisely determining the wear condition of the brake drums. It enables fast and simple measurement of the brake drum diameter or the amount of wear.

What is the maximum allowable brake drum diameter?

.120″
If the drum diameter is past the recommended limitations, the drum MUST be replaced. NOTE: WHEN CHECKING BRAKE DRUM DIAMETER FOR WEAR, THE DIAMETER SHOULD NOT EXCEED . 120″ OVER THE ORIGINAL DIAMETER. WHEN REBORING BRAKE DRUMS, THE FINISHED DIAMETER SHOULD NOT EXCEED .

How big can a new brake drum be?

For example, this usually means the drum may be turned a total of 0.080 over the brake surface diameter of a new brake drum. Example: New Drum Diameter 16.500 Rebore Allowance 0.080 Diameter after rebore limit is reached 16.580 Wear Allowance 0.040 Maximum Diameter 16.620

Which is the best way to measure a brake drum?

A good indication is feeling for a lip on the drum. A brake drum micrometer is by far the best way to measure a drum but if you don’t have one of those this quick cheap and easy technique works well. Get a piece of wood or here I’ve used a piece of PVC pipe.

What do you need to know about brake rotors?

The brake surface diameter should be within the maximum diameter cast or stamped on the drum or minimum thickness cast or stamped on the rotor. C. The mounting holes and pilot must be round and true. D. The mounting surface must be clean and flat. CAUTION: If any of the above conditions are not met, the brake drum or rotor should be replaced. A2.

How to tell if your car brake drum is cracked?

1. The brake drum is cracked. 2. The brake surface is heat checked, grooved or worn beyond the rebore limit of 0.080 or maximum diameter. 3. The back plate is cracked. 4. The bolt holes elongated. 5. The brake drum is known to have been severely overheated. 6. The brake drum is out-of-round enough that truing would exceed rebore limit.