Car & Truck Brake Drums

Moving Ahead or in Reverse, Brake Drums Are Important

Drum brakes use friction caused by a set of pads that press outward against a rotating cylinder attached to a vehicle's wheel. This is called the drum, and it pairs with a brake shoe to slow and stop a vehicle whether it's moving forward or backward.

How do brake drums and shoes work together?

A brake shoe is a curved piece of metal that sits inside the drum and matches its curvature. In most cases, two brake shoes are positioned on opposite wheels. There is a primary shoe and a secondary one.

Brake shoes have a lining with material designed to offer maximum grip or friction against the brake drum. The three main options are organic, semi-metallic, and ceramic. When the brake pedal is pressed, brake fluid is pushed through the brake lines to the calipers located on each side of the wheel. They contain pistons that are pushed out by the hydraulic fluid. The pistons push the shoes against the inside of the drum. This creates friction to slow and stop the vehicle.

While many vehicles today use four-wheel disc brakes, many trucks and some compact cars still rely on drum brakes for the rear wheels. In addition, some hybrid and electric cars use regenerative braking systems, which reclaim energy to charge batteries. These regenerative braking systems sometimes use rear drum brakes for stopping.

Drum brakes contain fewer parts than disc brakes, so they are less expensive and easier to maintain, but also less effective in stopping the vehicle. Most vehicles rely on the front brakes for most of the stopping ability.

Most modern drum brakes use an automatic adjusting screw to slowly move the brake shoes closer to the brake drum to offset the increased distance caused by wear. The distance can be manually adjusted by removing the tire to access the brake shoes. After removing the tire, you can pull off the brake drum and access the adjuster.

When you use a drum brake continuously, such as on a long, steep hill, heat and friction wear out the shoes. The brakes may suddenly lose power, causing you to exert more effort by stepping harder and longer on the brake pedal. Fortunately, brake fade is usually temporary. To restore fading brakes to normal functioning, you can go downhill in lower gears or pull over to let the brakes cool. Drum brakes are more prone to fading than disc brakes because they are enclosed and don't allow heat to dissipate as easily.

Friction is created when the brake shoe is forced against a moving brake drum, and friction generates heat. In extreme situations, the drums can glow red and crack from the heat. Excessive heat from continuous and rapid braking at high speeds can result in excessive wear to the braking system.

No. Brake rotors are components of a disc brake system. Drum brakes contain a rotating drum with two brake shoes that create friction. Rotors are flat discs squeezed by brake pads for friction.

Yes. A brake drum can be resurfaced, drilled, or patched. Over time, heat from friction can cause a brake drum to become uneven or warped, and the cost to repair it may be similar to the cost of replacing it.

Brake systems for trailers require different considerations. While drum brakes are less expensive, they are also less effective for stopping heavy trailers. Disc brakes are more resistant to fade, so they can be effective even when hot. Also, consider the vehicle towing the trailer when deciding on the best braking system and how to integrate it with the vehicle's brakes.

Electric drum brakes are the standard trailer option. An electric-over-hydraulic drum brake uses a small pump to increase the trailer braking pressure. The premium approach is to install electric-over-hydraulic disc brakes, designed for heavy loads and shorter stopping distances.