When to Change Your Brake Drums

A red sports car.

On most cars, brake drums are found in the rear wheels. This is primarily because of their relatively low cost and the ease of a parking brake to connect to them. Like all brake system components in a car, they wear down from time to time and need to be replaced. Since the brakes are arguably the car’s most vital safety feature, brake parts should never be allowed to fail. Rather, timely repair or replacement is always the best course of action. There are two telltale signs that your brake drums need to be replaced, indicated by noise and feeling.

How Brake Drums Work

Brake drums consist of the outer layer of the drum, two brake shoes, a wheel cylinder containing two pistons, and an adjuster arm. When you press down on the brake pedal, it compresses brake fluid which in turn puts pressure on the individual wheel cylinder. The pressure forces the pistons out which pushes the brake shoes up against the interior lining of the drum. The adjuster arm allows the shoes to be pushed into the drum with more force while also spreading out the surface contact. Numerous springs are found inside of the drum which pull the shoes off the interior once braking is complete. It also controls the adjuster arm and position of the shoes.

How You Know When Drum Brakes Fail

There are two basic ways to tell when drum brakes are not working effectively and need either to be repaired or replaced. The first is by listening. As brake shoes wear down, they start to squeal each time you apply the brakes. This may either indicate the need to resurface the interior of the drums or replace the shoes. Another noise that you do not want to hear is grinding. Grinding means that metal is rubbing against metal. The shoes have worn down sufficiently to be digging into the interior of the drum. At worst, both shoes and drums will have to be replaced when this happens. At best, the shoes will need replacing and the drums will need resurfacing.

The other way you can tell your brake drums need work is by the way the pedal feels when you apply it. Due to the way that the shoes are compressed into the drums, they do not necessarily wear evenly. This eventually causes the interior of the drums to get “out of round.” In other words, the interior of the drum is no longer a perfect circle. Each time you press the brakes, you feel this unevenness as the shoes rub against the inside of the drum. This tells you that the drums need resurfacing although not necessarily replacement.

It is important to take care of the brakes as soon as you know something is wrong. Not to do so can lead to increased repair or replacement costs in the near future as well as increased stopping time and the potential for a serious accident.