How Car Brakes Work

In a car, the brakes are used to slow down or stop quickly. The driver presses on the brake pedal and disengages the engine so that gas can be released from each of its cylinders in order to create pressure waves which push back against your vehicle’s movement, effectively slowing it down

The “how do car brakes work diagram” is a step-by-step guide to how car brakes work. It includes diagrams and text explaining the process of how braking is achieved in cars.

A vintage car applying breaks.

Welcome back to Gearhead 101, a series aimed at educating automotive newbies on the fundamentals of vehicle operation.

If you’ve been following Gearhead 101, you’re familiar with how a vehicle engine works, how it distributes power to the drivetrain, and how a manual or automatic gearbox acts as a power switchboard between the engine and the powertrain.

Today, we’ll talk about an automobile system that you use hundreds of times a day and that, if it fails, might kill or badly hurt you.

I’m referring to your brakes.

Using Motion to Create Heat

The physics of automobile brakes are straightforward. Your braking system converts kinetic energy (the movement of your wheels) into thermal energy (the friction provided by your brakes to the wheels) to slow and stop your automobile. Your automobile comes to a complete stop after the brakes have turned all of the kinetic energy of the wheels into thermal energy.

It’s quite straightforward.

However, there are two ways to skin this motion-to-heat-energy cat, plus a few more pieces that make both of them function. 

Brake System Components in a Car

Illustration showing the break system of car.

Pedal for braking. The brake pedal is something you’re acquainted with. It’s the foot-operated lever that allows you to slow down and stop the automobile. In most contemporary automobiles, the brake pedal is connected to a…

Booster for the brakes Most modern automobiles feature what are known as “power brakes.” Power brakes boost the force supplied to the rest of the braking system as a result of your pushing on the pedal. That implies you won’t have to exert too much force on the brake pedal to slow or stop your vehicle. Power brakes are made possible by the brake booster.

Vacuum-assisted boosters and hydraulic-assisted boosters are the two kinds of brake boosters. Vacuum-assisted boosters use the engine’s air intake to produce a vacuum. The force generated when you depress the pedal is amplified by the vacuum, which is applied to the master cylinder pistons (more on that in a bit). Hydraulic-assisted boosters enhance the force to the master cylinder by using hydraulic pressure from your car’s power steering.

So you put your foot down on the brakes. The brake booster amplifies the force provided by that operation. This force is transferred to the braking system via the brake booster…

Car engine in illustration.

Cylinder master. You’ve probably seen the master cylinder beneath the hood of your automobile, but you didn’t know what it was called. The braking fluid in your automobile is stored in the master cylinder. Brake fluid travels via brake lines to each of your car’s wheels. When you press down on the brake pedal, energy is boosted by the brake booster, which pushes a piston within the master cylinder, forcing brake fluid out of the master cylinder and into the brake lines that go to each wheel. The brakes on your wheels are then activated by the fluid.

The master cylinder ensures that all four brakes get equal hydraulic power. If one brake received more power than the other, uneven braking pressures would develop, resulting in a dangerous deceleration or stop. Consider what would happen if your car’s right wheels slowed down quicker than the left wheels. You’d fishtail or maybe overturn the vehicle.


Most current master cylinders have two reservoirs, one filled with brake fluid and the other with brake fluid. This is referred to as a dual braking system. It serves as a failsafe in the event that the front or rear brakes leak or get clogged with fluid.

One reservoir in the master cylinder has lines running to the front wheels, while the other reservoir has lines connecting to the back wheels on rear-wheel drive automobiles. Even if the lines going to the front wheels leak, fluid will still flow from the reservoir to the back wheels.

A diagonally split hydraulic system is used in front-wheel drive autos. Because the front brakes provide 90% of the braking in front-wheel-drive automobiles, this is true. You’d have a terrible time slowing down and stopping if both front brakes failed on a front-wheel-drive vehicle. The front-right wheel and rear-left wheel are connected together, and the front-left wheel is tied together with the rear-right wheel, to guarantee that at least one front brake stops the vehicle in the case of a leak or obstruction.

Of course, none of the brakes will operate if both reservoirs and the brake lines flowing out of them are leaking or obstructed. This is referred to as a catastrophic braking failure.

Lines for braking. Brake lines are steel tubes that go from the master cylinder to each of your car’s four wheels’ brakes. Brake fluid is sent to either a drum brake or a disc brake via the brake lines. The brakes are activated by the fluid pressure.

Internal view of break drum.

Brakes with a drum. Drum brakes and disc brakes are the two kinds of braking mechanisms used on automobiles. Drum brakes have been utilized in automobiles since 1900 and are still in use today. The wheel is attached to the drum brakes. Brake shoes are two heat-resistant pads that line the inner of the drum. When you push the brake pedal, brake fluid enters the wheel cylinder of the drum brake. Two tiny pistons within the wheel cylinder are then activated by the fluid, pushing the brake shoes out and pressing them on the braking drum. The drum is slowed by the pads, and the wheel is slowed by the drum (which is coupled to the wheel).

Drum brakes have various benefits, including being less expensive to manufacture and maintain, requiring less hydraulic pressure to activate, and lasting longer than disc brakes.

Drum brakes are still utilized on automobiles nowadays, as previously stated. Drum brakes are normally found on the vehicle’s rear wheels if it has them.

Illustration of a disc breaks.

Disc brakes are used. Drum brakes have the disadvantage of being self-contained. The heat generated by friction in the brake pads is retained inside the drum brakes. Drum brakes may get quite hot under extreme temperatures and repeated braking. If the brakes get too hot, they will no longer be able to provide the necessary friction to slow the vehicle down.

Engineers devised the disc brake to address this issue.


Disc brakes work in a very straightforward manner. When you use the brakes, brake fluid is sent to a piston on the disc brake. The piston squeezes the disc or rotor using the calipers. The friction created by the pads within the calipers slows your automobile down.

Disc brake calipers compress the brake pads in towards a metal disc connected to the wheel, rather than pressing against a drum to slow the automobile down. Squeezing in with calipers improves braking in a few ways. For starters, it enables you to apply greater pressure, which helps to increase friction. The disc brake design, on the other hand, is open. The brakes are not contained inside a drum. This enables the air to cool them down considerably faster, increasing friction in the process. Finally, the design allows for a larger brake pad surface area, which helps to enhance friction.

In 1951, racing vehicles were the first to employ disc brakes. They first appeared on mass-produced automobiles in 1955. Most automobiles, at least on the front wheels, had disc brakes by the 1980s.

Because all of the velocity is directed towards the front wheels when you brake, your front wheels perform the majority of the effort in stopping the automobile. Because the front wheels conduct the majority of the braking, disc brakes are installed on the front wheels because they are more effective than drum brakes.

Putting Everything Together

So, let’s put all of the braking system’s pieces together.

You put your foot down on the brake pedal. This engages the brake booster, which boosts the force generated by the brake pedal. The master cylinder receives the force from the piston. A piston in the master cylinder pumps braking fluid to each wheel through brake lines.

If a wheel has a drum brake, the braking fluid will contact a piston in the wheel cylinder, causing another piston to activate, pushing the brake pads against the brake drum. The automobile slows down or comes to a complete halt. The brake fluid will flow back into the master cylinder when you remove the brake pedal, and the brakes will release.

If the wheel is equipped with a disc brake, the braking fluid will activate a piston, causing calipers with brake pads to press against a disc, or rotor, connected to the wheel, slowing the vehicle. When you let off of the brake pedal, the brake fluid returns to the master cylinder, forcing the disc brake calipers to reopen.

That’s how your car’s brakes operate in a nutshell.

What Are the Advantages of Antilock Brakes?

Illustration of an antilock breaking system.

But hold on, there’s more. Antilock brakes are almost certainly installed in your vehicle (ABS). When you pushed on the brakes before ABS, your wheels came to a full halt. They shut the door behind them. Your tires began to slide as a result of this. You have little or no control over the automobile while a tire is sliding. So, if you were driving a vehicle in 1950 and had to slam on the brakes to avoid striking a child who ran out into the street, you’d still slide ahead and have no ability to turn the car left or right. When using the brakes on an ancient automobile, you would have to continually pump the brake (to repeatedly release and lock up the wheels), which is easier said than done.


ABS employs a microprocessor and sensors near each wheel to monitor wheel speed and prevent tire sliding. When you apply a lot of force to the brake pedal, the ABS system checks each wheel’s speed separately. If one of the wheels is moving slower than the others, that wheel is most likely locked up. As a result, the ABS system will lessen the hydraulic pressure applied to that brake, enabling it to spin again and avoiding a skid while maintaining steering control.  

When you press the brake pedal, you may feel the brake pulsing, which means your ABS is functioning. Don’t be concerned. Continue to apply pressure. On automobiles with ABS, you don’t want to pump the brakes because they won’t operate effectively.

When you purchase a new automobile, it’s a good idea to have a feel for the ABS system so you’re not surprised when it engages for the first time. You can try this by slamming on the brakes in an empty parking lot when it rains or snows (which will cause some sliding).



The “brake system parts and function” of a car is an important part of the vehicle. The brake system is made up of a number of different parts that work together to stop the car.

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