What are Brake Shoes?
Brake shoes convert your car’s kinetic energy to thermal energy by use of 'friction.' When a brake shoe is heated up in contact with a drum, it starts to transfer small amounts of friction material to the drum. The brake drums (both now with friction material on), will then 'stick' to each other to provide stopping power. The friction of the shoe against the drum is responsible for the majority of stopping power.
How do Brake Shoes Work?
Brake shoes are positioned inside the brake drum and are attached to the backing plate using hold down hardware. Each drum brake assembly consists of a leading and a trailing brake shoe, both actuated at the same time through hydraulic pressure applied by the wheel cylinder. When you apply pressure to the brake pedal, hydraulic fluid is placed under pressure and transfers energy to the wheel cylinder. Pressurized brake fluid pushes the wheel cylinder pistons outward, moving the brake shoes into contact with the inner brake drum surfaces. Brake shoe contact with the drum causes friction, resulting in braking action and reduction of speed. The more pressure applied, the greater the braking force and heat generated.
How are Brake Shoes Made?
Brake shoes utilize a variety of organic and metallic materials to form friction material. These are combined with a binder material that keeps friction material from shedding or breaking under pressure and heat. The friction material is bonded to a metal shoe. The shoe forms the guides for the friction material to precisely fit into brake drum as well as forming the contact surface for the wheel cylinder pistons. Drum brakes are typically found on your car’s rear wheels and often incorporate a mechanical parking/emergency brake mechanism that operates independently of the hydraulic system.
Why do Brake Shoes Fail?
- Normal wear and tear caused by friction
- Contamination of brake shoe friction material. This occurs when an axle seal leaks gear oil into the drum area.
What are Symptoms of Brake Shoe Failure?
- Dark friction surfaces
- Burnt odor
- Loud squeaking, squealing, or grinding noises
What are Consequences of Brake Shoe Failure?
- Reduced braking efficiency
- Dangerous driving conditions