How to Inspect a Brake Drum

Brake drum inspection is one of the most important safety inspections for a car. Your brakes need to work properly to stop your car. The brake drums absorb heat and dissipate it, so they can be weakened if their cooling surface area is reduced by distortion.

Difficulty: Moderately Challenging

Instructions

1. Remove brake drum. You'll find the drum's maximum diameter stamped onto the outside of it.

2. Wipe out dust with damp cloth. You'll need an approved brake cleaner because brake dust may contain Asbestos. When you finish using the cloth, dispose of it.

3. Inspect drum. You need to check for cracks, deep grooves, roughness or scoring. These may appear to be small discolored areas.

4. Smooth slight scores with fine emery cloth. Light scoring of the drum of less than .020 inches in depth won't affect your brake's operation. A mechanic should resurface heavy or extensive scoring.

5. Measure drum for taper and out-of-roundness. You need to measure with a drum micrometer at the open and closed edges of the friction surface and at right angles to each other. Even though you may not see the out-of-roundness with a visual inspection, you may find the measurements show it has an egg shape.

Tips & Warnings

• Brake dust may contain cancer causing Asbestos, so you'll need to use a damp cloth with an approved brake cleaner. Compressed air or lung power can make Asbestos airborne. Throw away cloth after use.
• Replace drums with more than .006 inches of taper or out-of-roundness.
• Cracked drums must be replaced. Even though fine cracks are hard to see, you'll need to replace your brake drums.

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