A brake drum is a metal drum that is used in conjunction with a brake drum friction component known as brake shoes. The drum rotates with the road wheel, and the shoes which are fitted inside the drum are stationary; when the foot brake is applied, the shoes are forced against the inner surface of the drum wall, which slows and stops the wheel.
The brake drum plays a pivotal role in the parking brake operation also. While drum brakes were once the only type of brake available, they are no longer commonplace.
In fact, most modern vehicles employ calipers and rotors, which have largely replaced brake drum technology.
Where’s a Brake Drum Located?
While not as common as they were, drums are still fitted to some vehicles; however, you will only find them on the rear wheels of a vehicle, never at the front.
As modern cars employ an open-spoked wheel design, it is possible to identity which type of brakes your vehicle has without removing the road wheel.
As said, the drums, if fitted, will only ever be fitted to the rear of your vehicle.
Common Brake Drum Problems
Brake drums are tried and trusted and are low technology and, as such in themselves, don’t suffer from major issues. Typically, the only trouble caused is drum wear.
Brake drums employ an inner machined surface that interfaces with the brake shoes. It’s this surface that wears out, gets market, and gets out of shape. The surface may be machined or turned, it’s a process of removing a thin layer of metal, but the machining process importantly makes the drum true again.
Brake drums are marked with a minimum inner drum size; a drum that’s below this number is, as you’ve guessed, at the end of its useful life and not suitable for machining.
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John Cunningham is an Automotive Technician and writer on Rustyautos.com. He’s been a mechanic for over twenty-five years and has worked for GM, Volvo, Volkswagen, Land Rover, and Jaguar dealerships.
John uses his know-how and experience to write fluff-free articles that help fellow gearheads with all aspects of vehicle ownership, including maintenance, repair, and troubleshooting.