How car brakes work

1. Your foot pushes on the brake pedal.
2. As the pedal moves down, it pushes a class 2 lever (a kind of simple machine), increasing your pushing force.
3. The lever pushes a piston (blue) into a narrow cylinder filled with hydraulic brake fluid (red). As the piston moves into the cylinder, it squeezes hydraulic fluid out of the end (like a bicycle pump squeezes out air).
4. The brake fluid squirts down a long, thin pipe until it reaches another cylinder at the wheel, which is much wider.
5. When the fluid enters the cylinder, it pushes the piston in the wider cylinder (blue) with greatly increased force.
6. The piston pushes the brake pad (green) toward the brake disc (grey).
7. When the brake pad touches the brake disc, friction between the two generates heat (red cloud).
8. The friction slows down the outer wheel and tyre, stopping the car.

In practice, the pedal operates four separate hydraulic lines running to all four wheels. We're just showing one wheel here for

Typical brake maintenance

Many consumers are surprised to find themselves being told that they need new brakes before the manufacturer's warranty has even expired. Many more are surprised to find that they only need to replace the front brakes, while the rear brakes can be replaced later. Brakes are one of the most important aspects of vehicle performance--and one of the most misunderstood.

Why Front Brakes Fade Faster

Most cars use a front disc/rear drum brake setup, although most sports cars and most premium sedans use disc brakes at all four wheels. Disc brakes use a circular rotor (the disc) that rotates with the wheel. When the brakes are engaged, a set of pads that are attached to a caliper clamps down on the disc to help bring the vehicle to a stop. Drum brakes use pads--called "shoes"--that are mounted inside a round "drum." Those shoes push out against the rotating drum in order to provide stopping power for the car.

Because most of the vehicle's weight shifts to the front during braking, that means that the front brakes have to handle most of the work. That also means the front brakes wear faster--sometimes as quickly as 30,000 miles.

Brake wear will also vary on different types of driving. Aggressive drivers who slam hard on the brakes will obviously wear their front brakes out faster than those with a more sanguine style. Also, drivers who spend a lot of time in stop and go urban traffic will wear their brakes out faster.

Rotor Repairs

When worn-out disc brake pads are replaced, the rotors are usually machined or "cut." This is because the metal goes out-of-round over time. This often causes the brake pedal to pulsate when the brakes are activated. This is a condition often described as "warped" rotors.

What will happen if you neglect to maintain your brakes

Driving may be fun, but being able to stop is what keeps drivers alive. Unfortunately, many drivers neglect brake maintenance until it is time to call the insurance company.

Your brakes will tell you when they need some attention, have your brakes checked out if you can

answer yes to any of the following symptoms:

And give this information to the mechanic when you go...

Do you feel your brakes pull in one direction?
Do you have to push the pedal farther or harder than normal?
Does the pedal feel "spongy" when you push on it?
Do you hear squealing, grinding, scrapping or chirping noises?
Do you smell anything different?
Do the brakes "grab"?
Does the pedal pulsate when you push on it?

Most people religiously change engine oil, engine coolant and transmission fluid, but never give a thought to their brake fluid. It is estimated that about half of the cars and light trucks on American roads over ten years old still have the brake fluid that was installed at the factory. Of all fluids in a vehicle, brake fluid most directly affects safety. Neglect engine oil and you risk your engine; neglect brake fluid and you risk your life.