The car’s braking system ensures safe braking and stopping under all driving conditions. Modern vehicles have a reliable braking system for this purpose, which is made up of various components. Find out now everything about the structure, function and components of the car brake system.

Structure and types of brake system

Nowadays, a modern car brake system is designed as a hydraulic system. Only in old vehicles such as vintage cars are brakes still operated by rods or cables. A pneumatically actuated brake system with compressed air, on the other hand, is usually only used in trucks. Depending on the vehicle model, the design and components of the installed brake system can differ.

Hydraulic brake system in passenger cars

The brake system in modern cars consists of a closed brake system with hydraulic actuation. Brake fluid is used to transmit the braking force from the brake system pedal to the brakes on the wheels. The pressure required for braking is generated by a master cylinder as soon as the driver presses the pedal. Brake hoses and lines under the vehicle floor ensure that the brake pressure is reliably transmitted to the individual wheel brakes. A brake fluid reservoir ensures that there is always enough brake fluid available. This reservoir also acts as the equalization reservoir for the hydraulic brake system. A cap with a screw cap allows brake fluid to be refilled if necessary. The so-called service brake is used exclusively to decelerate the car while driving. Depending on the vehicle, the brake pedal may also have to be depressed in order to start the engine. However, an additional braking device to secure the vehicle when stationary is mandatory. This parking brake can be activated electrically or by brake cable.

Brake booster and wear indicator

Many cars today are equipped with a brake bo oster. This component of the braking system reduces the necessary pedal force when braking and makes it easier for the braking effect to occur. In order to keep a constant eye on the wear of the brake pads, some vehicles are equipped with a wear indicator. This often works purely mechanically and produces a loud squealing noise. Other systems work with an electronic wear indicator.

Disc brakes or drum brakes

Passenger cars are equipped with either disc brakes or drum brakes. In modern vehicles, however, drum brakes are only used on the rear axle. In addition, this form of vehicle brake is now only installed in some small cars. A disc brake system has brake discs that rotate together with the respective wheel. A brake caliper encloses the brake disc from the outside and brakes it through friction by means of a brake pad. Drum brakes press the lining against the brake drum from the inside.

Brake system with two brake circuits or ABS

All newer cars have two brake circuits, each operating one of the brakes on the front axle and one on the rear axle. This system is mandatory. If one brake circuit is defective, for example because brake fluid is leaking, the second circuit provides the required braking force. Modern vehicles are invariably equipped with the ABS anti-lock braking system. This system prevents the wheels from locking during braking. For this purpose, corresponding brake systems have additional components such as ABS sensors and ABS control unit.

Brake parts and components

Today, the braking system in a passenger car is made up of numerous components. The various parts of the braking system work in perfect harmony with each other. In this way, the driver can reliably initiate and precisely execute every braking process. The most important parts of the brake system are listed in the following overview.

• Brake pedal: The brake pedal is used for finely metered actuation of the brakes. In almost all cars, the brake pedal can be found in the driver’s footwell to the right of the accelerator pedal.
• Master brake cylinder: The master brake cylinder is connected to the brake pedal. When the driver applies the service brake, the cylinder builds up pressure in the brake system.
• Brakelight switch: This switch turns on the brake light at the rear of the vehicle when the brakes are applied. The brake switch is installed in the area of the brake pedal behind the dashboard.
• Brakedisc: The brake discs are a component of the brake system with disc brakes. The brake disc rotates with the wheel and is decelerated by the brake pad through friction.
• Brake pads: The brake pad provides the necessary friction and thus deceleration during braking. The brake pads are firmly connected to the brake pad or brake pad carrier.
• Brake caliper: As part of the disc brake, the brake caliper holds the brake pads. During braking, the brake caliper presses the brake pads against the brake disc.
• Brake booster: The brake booster makes braking easier by reducing the amount of force the driver has to apply. The component is usually found behind the pedal in the engine compartment.
• Brake lines: The brake system lines transmit braking force to the brakes. Flexible brake hoses are installed there so that the wheel suspension remains movable.
• Brake drum: The brake drum is part of the brake system on vehicles with drum brakes. The drum rotates with the wheel and holds the brake components.
• Brake shoes: The brake pad carriers of the drum brake are called brake shoes. During braking, internal wheel brake cylinders press the brake lining against the drum.

How a car brake system works

The hydraulic passenger car brake system is operated by the driver via the brake pedal. This allows finely metered braking or a quick stop in an emergency. When the driver presses the pedal, the master cylinder connected to it builds up the pressure required for braking. In a brake system with disc brakes, the brake pressure acts on brake pistons, which press the brake pads against the brake disc via the brake caliper. In the case of drum brakes, the pressure is transmitted to the brake cylinders inside the brake. The brake shoes mounted here press the brake pads firmly against the inside of the brake drum by pressure from the pistons.

Function of the parking brake

The hand brake or parking brake differs in its function from the rest of the brake system. This brake is not used to reduce the speed of the vehicle while driving. Instead, it secures the car when it is parked or stopped. The parking brake is operated by a handbrake lever or handbrake pedal. Unlike the service brake, this brake only affects the rear axle. Older vehicles have a handbrake cable installed, while newer vehicles have an electric brake as a parking brake.

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