How do Brake Drums Work?

The brake drum fastens via a flange arranged perpendicular to the braking surface to the axle flange. The inner surface of the drum rotates with the road wheel and at the exact rotational speed of the wheel. When hydraulic or mechanical actuation of the brake shoes (friction) occurs, the shoes are pressed into contact with the braking surface that comprises the inner surface of the drum. Friction material (shoes) contact with the drum creating interference that impedes the motion of the road wheel, thereby creating the braking action. The harder the brake pressure, the more braking power (and heat) from the brake drum. Braking force is transferred from the brake shoes through the drum and into the road wheel.

Why do Brake Drums Fail?

• Wear and tear
• Excessive heat
• Severe rust

What are the Consequences of Brake Drum Failure?

• Drums that are cut beyond the safety maximum diameter are thin, do not have adequate structural strength, and are unable to dissipate heat properly. Such a brake drum can fail without warning and are not safe.
• Out-of-round brake drums that cannot be adequately machined reduce braking effectiveness and are not safe to drive on.