How do car brakes work?

Most cars will have disc brakes on their front wheels and either disc or drum brakes on their back wheels.

With disc brakes, when you press the brake pedal, the hydraulic brake fluid makes the brake caliper push the brake pad against the brake disc. As the brake pad rubs against the brake disc, the friction slows down the wheels.

What are the parts in a car's braking system?

● Brake discs - Metal discs that rotate along with the wheel.

● Brake pads - Pads on either side of the brake discs that cause friction when the brake pedal’s pressed.

● Brake calipers - Contain the piston and brake pads. They clamp onto the disc when braking.

● Brake lines - Transport brake fluid through the braking system.

● Brake fluid - Fills the brake lines and uses hydraulic pressure to activate the calipers when the brake pedal’s pressed.

● Brake master cylinder - A hydraulic piston attached to the brake pedal to pressurise the braking circuit and activate the brakes.

● Brake servo - Attached to the master cylinder, it uses vacuum generated by the vehicle's engine or a pump to increase the pressure when the brake pedal's pressed.

Disc brakes vs drum brakes

Disc brakes are more expensive than drum brakes and are usually considered to be better. Braking creates a lot of heat which needs to escape quickly. Disc brakes work well because they:

● Have a more open design which lets in air to cool them down and makes them less likely to overheat.

● Work better in wet conditions.

● Are less likely to lock up.

It’s normal to see discs at the front, where they do most of the braking. Cheaper drum brakes are often used on the rear wheels as parking brakes. Larger or more powerful cars tend to have disc brakes on all 4 wheels.

Parking brakes

A car's handbrake activates a cable which squeezes the rear brake pads closed and stops the car moving. Some cars have separate discs and pads specifically for the handbrake.

Other cars have an electronic parking brake which uses a button instead of a handbrake. The car’s handbook will show how to release the brakes if the car battery's flat.

ABS brakes

Anti-lock brakes include a sensor on the wheel hub which senses how fast the wheels are going. When you brake, the ABS senses if the wheels are about to lock. An ABS pump, with a piston for each wheel, rapidly pulsates pressure to the wheel(s) about to lock. That prevents the car from skidding and helps the driver to maintain control.

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