The brake system in your vehicle allows the driver to slow down or stop in a consistent and reliable manner. The brakes on your car work by converting the kinetic energy of movement into thermal energy (heat).
Each time you step on the brake pedal, the speed of the spinning wheels underneath your vehicle is reduced proportionately to how much pressure you apply to the pedal. A vehicle will have either a disc brakes or drum brakes to create the necessary friction for this to take place.
Modern car brake systems are referred to as power brake systems. These systems use a brake booster that amplifies the force you apply to the brake pedal. This makes braking so much easier for drivers. Power braking allows you to apply just a little bit of pressure to the brake pedal in order for the vehicle to slow down.
In the classic mechanical brake system, there was a cable which connected the brake pedal and brake shoe assembly together. When the driver stepped on the brake pedal, it pulled on the cable and allowed the brake drum spinning to slow down. This was used on cars in the early 20th century, and is still used on bikes today.
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Car Brake System Components
Below is a list of the main parts of a car brake system. We have included both the components of the disc and drum brake systems. Most modern vehicles have disc brakes on all four corners, but some economy cars still use drum brakes in the rear.
1) Master Cylinder
The brake master cylinder pushes hydraulic fluid down into the brake lines from the brake fluid reservoir.
Most master cylinders are actually split into two or more individual cylinders for safety reasons. Typically each cylinder manages the braking ability of one front wheel and the opposite rear wheel. That way, if one cylinder fails, the other cylinder can still slow down the car and allow the driver to maintain a reasonable amount of control.
Some vehicles will use one cylinder per axle (front/rear split). Others use multiple cylinders per wheel for maximum redundancy in case of a failure.
The master cylinder works by managing the amount of hydraulic pressure that is placed on the hydraulic fluids. More pressure will slow down the vehicle more quickly.
2) Brake Rotor (Disc Brakes)
Each wheel of a vehicle has a brake rotor that spins while the vehicle is in motion. The brake pad and caliper come into contact with the rotor, creating the necessary friction to slow down the disc. This action subsequently decelerates the wheel and the entire vehicle.
Brake rotors are typically made out of cast iron. Although cast iron is quite heavy, it has the ability to absorb a significant amount of heat. To aid in heat dissipation, many rotors are designed with vents.
These vented rotors feature openings or vanes situated between the two discs. These vents direct airflow into the rotor, effectively cooling it as it rotates. Rear brakes typically utilize solid rotors since they generally perform less work in stopping a vehicle.
3) Brake Drum (Drum Brakes)
The brake drum is the alternative to a brake rotor when you have a drum brake system. So how does it work?
As your car’s wheel spins, the brake drum component rotates along with it. When you hit the brakes, the brake shoe is pushed against the inside of the drum, creating friction and bringing your car to a stop. It’s a simple but effective system that has been used for decades.
While drum brake systems are not as common as they used to be, they are still found on some vehicles today. And for those who prefer the simplicity of this type of braking system, the brake drum remains a reliable and effective alternative to the more modern brake rotor.
4) Brake Pad (Disc Brakes)
In a disc brake system, the brake pad and its caliper create friction as they rub against the spinning brake disc.
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5) Brake Caliper (Disc Brakes)
Brake calipers provide the clamping force that pushes the brake pad into the brake rotor. This is achieved by using hydraulic pressure.
The hydraulic pressure from the master cylinder pushes brake fluid down the brake lines and into one or more pistons housed in the brake caliper. When you step on the brake, these pistons push on the brake pads with a great force.
6) Brake Shoe (Drum Brakes)
This is the alternative to the brake pad when you have a drum brake system.
Unlike brake pads, which are flat and attach to a brake caliper, brake shoes are curved and fit inside the brake drum. As the drum rotates, the brake shoe is pushed against it, creating the necessary friction to bring your car to a stop.
7) Brake Booster
The brake booster (also called a vacuum servo) is part of the power braking system and it uses either engine vacuum or a vacuum pump to amplify the foot pressure you place on the brake pedal.
This means that you don’t have to apply as much pressure to the pedal to slow down your vehicle. It’s like having a helping hand to make braking easier and more efficient.
The brake booster is a game-changer for modern cars, making it easier for drivers to brake smoothly and quickly in any situation.
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8) Brake Pedal
The brake pedal is one of the most important components of your car’s braking system. Located next to the gas pedal, it’s the pedal you step on to slow down or stop your vehicle. But did you know that the brake pedal is connected to the entire braking system on the inside?
When you press down on the brake pedal, it activates the master cylinder, which in turn sends hydraulic fluid to the brake calipers or wheel cylinders. This creates friction between the brake pads and rotors, or brake shoes and drums, which slows down your vehicle.
9) Wheel Speed Sensors (ABS)
Vehicle equipped with an anti-lock braking system (ABS) have wheel speed sensors which detect how fast each wheel is spinning. If your wheels lock up because you slam on the brakes, one or more wheels will be spinning at different speeds.
This speed difference is used by the ABS module to determine how to apply individual brakes to bring your car to a safe, controlled stop.
10) ABS Module
An ABS module is a computer for the braking system. This computer modulates the brakes when one or more tires are at the limit of traction on vehicles equipped with anti-lock brakes.
The ABS module uses input from the wheel speed sensors and possibly other sensors, depending on the manufacturer’s programming. When a tire starts to lock up, the ABS module will release brake pressure to that specific wheel, allowing the tire to regain traction.
Remember that a rolling tire has more grip than a sliding tire. The ABS system gives a driver the ability to stop as fast as possible, even when they stand on the brakes as hard as they can.
11) Brake Lines
Brake lines transfer brake fluid between the master cylinder and wheels. This is the hydraulic fluid that allows braking to be so easy.
Unlike air, hydraulic fluid is not compressible. That means when you push on the brake pedal, that force is directly transferred to the piston in the brake caliper, or shoe in the brake drum.
A brake fluid leak is potentially dangerous as it may introduce air in the system. When there is no brake fluid, the brakes will not work effectively.
Importance of Brake Fluid
While not exactly a component of a car’s brake system, brake fluid is just as important as any other part. Brake fluid is a type of hydraulic fluid that transfers pressure from the master cylinder down to the brake components on each wheel.
It’s important to know that brake fluid is hygroscopic, which means it can attract water. This is a bit of a problem because water can cause corrosion and damage rubber seals. Because of that, you’ll want to make sure that you periodically check the brake fluid level (and condition) in the reservoir to keep everything running as it should.
Speaking of the brake fluid reservoir, this little container sits on top of the master cylinder and supplies it with fluid. Whenever you press the brake pedal, the master cylinder forces fluid out of the reservoir along the brake pipes to the slave cylinders at the wheels.
Materials Used in Brake Systems
Let’s talk about the materials that are commonly used in brake systems.
First of all, rubber is vital in creating the brake hoses and seals within your braking system. You know those flexible brake lines that connect the master cylinder to the brake calipers and wheel cylinders? That’s where rubber comes in.
This material allows the lines to flex when your car’s suspension moves. In addition, the rubber seals within the system help maintain pressure and prevent fluid leaks.
Cast iron is the go-to material for brake rotors and drums found in most cars. It’s popular because it delivers excellent heat dissipation and has enough strength to tolerate the friction and heat produced during braking. And here’s a bonus: cast iron is relatively cheap, making it an affordable option for both manufacturers and car owners.
Other materials used in braking systems:
- Aluminum – Found in some high-performance brake calipers, aluminum is lightweight and corrosion-resistant.
- Steel – Often used for constructing ABS modules, brake boosters, and various components that require strength and durability. Braided stainless steel brake lines are often used in high performance vehicles over rubber.
- Ceramics – These are used in some premium or high-performance brake pads, offering better heat management and reduced brake dust.