Brake System Components and their Functions

A brake system is the first safety feature of a vehicle. This system allows you to stop or slow down reliably and consistently. It is, therefore, crucial to know the various brake system components and how they work. This gives you confidence when driving and enables you to know when something is amiss in the braking system.

A vehicle’s braking system works by changing kinetic energy to thermal energy. When you press the brake pedal, the spinning wheels reduce proportionally depending on the pressure you apply. Vehicles have either a drum braking system or a disc braking system.

Whenever you start noting a problem in the braking system, the most prudent thing is to visit a mechanic. Having regular brake system checks will prevent it from more damage or other risky situations. Now read along to understand the various parts in the brake system and how they function.

brake system diagram

Brake System Components and Short Description

The brake system is used to decrease or decelerate the speed of a moving vehicle. This system uses hydraulic fluid for it to operate. It features many components that work together to ensure that you can stop at any given time you desire.

There are two types of brake systems. Older vehicles feature drum brake systems, while new models have disc brake systems. Drum brakes have a drum brake in the wheels, and disc brakes have brake rotors attached to the wheels. Some parts of the two brake systems are different, but most of the components are the same.

The brake system absorbs kinetic energy in the vehicle and electronically or mechanically to decrease its speed. In vehicles using electric brakes, an electric current pushes a magnet to apply brakes. For vehicles with a mechanical brake system, friction changes kinetic energy into heat.

Once you press a vehicle’s brake pedal, the oil moves to the wheels’ calipers and puts pressure on the caliper pistons. This pushes the brake pads against discs or rotors and causes friction. This then slows down the rotation of the wheels, causing the vehicle to slow down.

The performance of a braking system is calculated in stopping distance. Brakes of ordinary vehicles are less powerful compared to those of hyper-cars, and thus they require a longer distance to stop. Now let us discuss brake system parts and functions:

1. Brake Pedal

The brake pedal is an external part of the brake system located in the cabin next to the vehicle’s gas pedal. This is where you step when you want your vehicle to slow down. This part is connected to the whole braking system inside the car.

Vehicles with automatic transmissions have two pedals, namely a throttle and brake pedal. Manual transmission cars have three pedals, and the brake pedal is in the middle. The other two pedals on the side are throttle and a clutch.

The brake pedal size varies depending on the model and makes of the vehicle. However, the automatic vehicle tends to have larger brake pedals compared to cars using manual transmission.

2. Master Cylinder

A master cylinder acts as a hydraulic pump. It is situated at the end of the brake pedal. This brake component part feeds brake fluid to the circuit, which changes pressure on the brake pedal to hydraulic pressure.

The master cylinder is made up of several moving parts. You can understand this better by looking at the brake system components diagram.

Another purpose of the master cylinder is to provide brake safety. Most master cylinders feature two chambers. Each of these chambers operates on a set of wheels. They are designed in this way to maximize your safety. In case the brakes in one set of wheels fail, the other set is still powered.

Some vehicles today have multiple cylinders for each wheel. This creates maximum redundancy and offers safety in case one of the cylinders fails. The master cylinder manages how much hydraulic pressure is forced on the hydraulic fluid. Hydraulic pressure helps the vehicle to slow down more quickly.

The brake master cylinder also holds excess brake fluid. When you use the brakes, brake fluid enters the brake line making the brakes operate. Once you release the brake, the brake fluid returns to the reservoir, thus releasing the braking system.

The seals in the cylinder may wear out after some time of use. Some signs of a problem in the master cylinder are leaks, contaminated brake fluid, or malfunctioning of the brake pedal. If you experience any of these issues, get the vehicle checked by a specialist right away.

3. Brake Rotor

Another component in the brake system parts list is the brake rotor. This brake part is found in disc brakes. It resembles large metal plates and attaches to the wheels. It rotates when the car is moving.

Brake rotors act as a grip for the vehicle’s brake pads to clasp onto when calipers apply pressure after pressing the brake pedal. This slows the rotation of the wheels and makes the vehicle stop.

Brake rotors are made with cast iron. Since cast iron is heavy and absorbs a lot of heat, the rotor has vents to help in heat dissipation. The vent allows air to flow in the rotor, enabling it to cool as it spins. Rear brakes have solid motors since they do less work when the vehicle is stopping.

Brake motors can last for a long time depending on the vehicle’s age, conditions of other brake components, and driving conditions and habits. On average, brake rotors last between 30,000 to 50,000 miles.

The condition and quality of your brake rotors are vital for your safety and should be taken care of diligently. Some signs that the brake rotors may need servicing are visible rotor wear, change in brake pedal feel, burning smell, and noise from the brakes.

4. Brake Drum

A brake drum is a part of the drum brake system. It is an alternative to brake rotors when your vehicle is using the drum braking system. It is mostly made of cast iron, and it is resistant to wear and heat.

Brake drums are located along the brake shoes. When you press the brake pedal, the brake shoes expand, causing friction to the brake drums. This causes the car to slow down or stop.

The constant friction during braking causes it to wear. The material used on brake drums loosens, thus reducing the stopping power. After some years of driving, the brake drums may need replacing.

5. Brake Pads

Brake pads are found on disc brake systems with rotors. Every caliper on the vehicle has two brake pads. The pad presses the rotors causing friction which slows down the vehicle. The objective of this is to offer the calipers as much friction as possible.

Brake pads need to be replaced after a given mileage stated by the vehicle manufacturer. However, you may need to change it earlier if you hear some sounds when braking.

Softer braking pads offer a better braking system, but they need replacement after a shorter mileage. Worn-out or old brake pads decrease the functioning of the braking system significantly. Operating a brake pad above the heat range increases the vehicle stopping distance.

6. Brake Calipers

Brake calipers are important parts of the hydraulic brake system components. They work together with brake rotors on disc brake systems. You can view this part of the braking system externally. The brake calipers are reasonably large, but their size depends on the rotor’s size. Larger rotors need large brake pads and calipers.

The calipers offer clamping force which presses the brake pads toward the brake rotor to create friction. The brake caliper houses the vehicle’s pistons and brake pads. The caliper is situated inside the wheel and connects to the master cylinder through valves, hoses, and tubes, which conduct the brake fluid via the system.

The heat generated during the braking in the brake system can cause the calipers to weaken or break down their seals. Over time the calipers also become dirty, contaminated, or rusty leading to brake fluid leaks.

These issues affect the efficiency of the braking system, and the calipers will need to be replaced. You can remove brake calipers from the vehicle in case you want to repaint them. It is advisable always to use brake caliper grease to lubricate parts that get into contact with pistons and brake pads.

7. Brake Shoes

Brake shoes are parts of brakes in a car using the drum brake system. They are crescent in shape, and one of their sides is made with rough friction material. The brake shoes sit in the vehicle’s brake drum. When you press the brake pedal, brake shoes move outwards against the brake drum.

Brake shoes are mainly used on a car’s rear axle since most vehicles today brake sharply with their front wheel. This prevents the rear brakes from handling very high temperatures.

Brake shoes feature a slave cylinder that has a brake bleeder. You use the brake bleeder to remove any air that could be trapped in the brake shoe. This brake system component is mostly found in older vehicles.

Brake pads and brake shoes play a similar role but work differently. Brake shoes push outwards to stop a vehicle, but brake pads stop it by moving closer. A brake shoe features a rough-surfaced material and a large surface area but has less stopping power compared to brake pads.

8. Brake Booster

A brake booster is also called a vacuum servo. It is a component of the power braking system. It resembles a black canister with a circular shape. A brake booster improves the safety and performance of your engine. It is located behind the engine case between the master cylinder and the pedal.

It uses a vacuum pump or engine vacuum to amplify the pressure placed when pressing the brake pedal, making it easy for the vehicle to slow down. The vacuum balances the fluid pressure in the vehicle’s braking system, leading to effective braking.

There are two different diaphragms of brake boosters. Tandem brake boosters are for trucks and bigger cars, while single brake booster is used on smaller vehicles. A brake booster is a beneficial part of the brake system for people who drive a lot since it makes braking easy.

9. Wheel Cylinders

We have seen that one vital part of the braking system I the master cylinder. The master cylinder has four-wheel or slave cylinders. Wheel cylinders are located between the piston and brake shoes. Each of its ends is sealed with rubber to prevent dust from getting in.

Parts of wheel cylinders include a bleeder valve, protective caps, gaskets, compression springs, sleeves, and two or one pistons. It also has a housing made of wither aluminum or grey cast iron in new vehicle models.

The function of the wheel cylinders is to get pressure from the master cylinder through hoses and pipes and apply pressure to brake shoes or brake pads. Drum brakes have different cylinders that are located in the drum.

10. Brake Fluid Container

Another important brake system component is a brake fluid container. The purpose of this component is to contain the brake fluid. The color of the brake fluid should be brown or yellow. A dark-colored brake fluid means that it has an issue and it needs to be changed.

11. Brake Hose Pipe

The brake hose pipe is a part found in all vehicles. It connects the slave cylinders with the master cylinder. Most of these hose pipes are made from brass or copper. The reason they are made from these materials is that they are corrosion-resistant and withstands pressure.

Brake hose pipes are protected and held into place as they pass inside the vehicle. In case of the pipe breaks, the brake fluid loses pressure which prevents the brakes from working. Therefore, you need to check your brake hose pipes often and replace them as soon as you discover some issues.

12. ABS Module

ABS stands for Anti-lock Braking System. This part of the brake system prevents wheels from skidding and locking. All the new vehicles have been designed with ABS. Vehicles have sensors on all four wheels.

The ABS module is located in the engine. It records data got from the braking system and the four sensors. ABS then calculates the force to apply to prevent the vehicle from skidding.

When the wheel begins to clock up, the ABS module releases pressure to the tire and allows it to gain traction. ABS gives the driver ability to stop as fast as possible.


The car’s braking system composes of different components which work together for effective braking. Above, we have discussed different brake system components and functions. There are two types of brake systems known as the drum brake system and disc brake system. Most of the components are the same, but some are different depending on your vehicle’s braking system.

Drum brakes are found in older cars. They provide less performance because of the friction between the brake shoes and brake drum. Disc brake systems have calipers and rotors instead of brake shoes and drums. They are found in modern vehicles and are more efficient. Issues with the brake system should be dealt with immediately since it holds your safety.


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