Feb. 18, 22
The brake shoe is a brake component located inside the brake drum and is the “friction contact point” of drum brakes.
When you depress your brake pedal, the wheel cylinder in the drum brake engages, pushing the brake shoes outwards, against the inside surface of the brake drum.
This creates friction between the brake shoe lining and the brake drum — eventually stopping the vehicle.
When the brake is released, the retention spring pulls the brake shoe back in a resting position, allowing the vehicle to move again.
Without a functioning brake shoe, the other components of your drum brake system, like the backing plate, wheel brake cylinder, and parking brake, can quickly start to wear out.
The brake shoe is a curved metal piece with a layer of friction material, called the brake lining, on one side.
The brake lining is composed of relatively soft but tough, heat-resistant material with a high friction coefficient. It's similar to the friction material on the brake pads of disc brakes.
Each drum brake has one pair of brake shoes — a primary shoe (front brake shoe) and a secondary shoe (rear brake shoe). Sometimes their lengths are slightly different, or they may have different types of friction materials.
Inside a drum brake assembly, the brake shoes are mounted on the backing plate with the friction material facing outwards towards the brake drum. Most of the braking effort is handled by the rear shoe, which is why it's usually a little longer than the front shoe.
So, how is the drum brake shoe different from a disc brake pad?
Modern vehicles with a hydraulic braking system typically come with one (or both) of these braking mechanisms — the disc brake and the drum brake.
Disc brakes are usually mounted on the front wheels as they quickly exert braking force, which is critical during an emergency brake.
Remember that braking is the act of applying friction, where kinetic energy is converted into heat. This means that braking temperatures on the front brake disc tend to be higher than the rear drum.
As drum brakes don't dissipate temperatures as well as disc brakes, they're inserted on the rear axle where rear wheel braking temperatures aren't as high.
Excessive brake drum heating can cause brake fluid to vaporize — and this can reduce the hydraulic pressure applied to the drum brake shoes, making braking less effective.
They're also more effective as a parking brake than disc brakes and are less expensive to manufacture, so don't be surprised to find rear drum brakes on your ride!
It's important to note that disc brakes use brake pads. Drum brakes use brake shoes.
They can't be interchanged. That's the primary difference between brake pads and brake shoes.
Here's how the brake shoe and brake pad differ in terms of performance and durability:
Stopping power: The stopping power generated by a brake pad (in a disc brake system) is considerably more than the brake shoe. This is why it's used primarily in the front axle for emergency braking. Rear brakes typically handle a little less braking force.
The direction of force: Disc brakes use a caliper fitted with brake pads that “squeezes” the rotor to stop the wheel. Drum brakes, on the other hand, exert an outwards pressure by “pushing” the brake shoe against the brake drum.
Life expectancy: Brake shoes usually outlast brake pads as they are positioned inside the wheel rather than on the outside. Being on the outside, brake pads are far more exposed to the environment, like dirt, mud, and debris, which can cause wear and tear, reducing the lifespan of the brake pads much faster.
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