CHAPTER 3 - PART 3 - CHASSIS - BRAKING SYSTEM

The braking system is designed to reduce the motor vehicle's road speed, enable effective braking on downhill or uphill gradients and hold the motor vehicle stationary, including on sloping roads.

According to its functional role, the braking system can be classified as:

• main braking system - comprises the service brake, which is operated using the brake pedal;
• parking brake system - holds the motor vehicle stationary, including on downhill or uphill gradients, when it is stopped or parked;
• auxiliary braking system - consists of retarders that help maintain a constant speed when descending long slopes, without prolonged use of the service brakes. This system is fitted to heavy motor vehicles.

The braking system is a complex assembly consisting of:

• actuation system: transmits and amplifies the force applied to the brake pedal. The force exerted by the foot is transmitted through the pedal to the brake servo, and the brake master cylinder converts this amplified force into hydraulic pressure using the brake fluid;
• pressure transmission system: receives the hydraulic pressure generated by the brake master cylinder and transmits it through the brake fluid to the wheel brake mechanisms via pipes and hoses;
• mechanical wheel braking system: operates the braking devices, pressing the brake pads against the discs and the brake shoes against the drums.

The disc brake consists of:

• brake discs;
• brake pads;
• brake callipers.

In some motor vehicles, the disc brake may also be fitted with brake pad wear sensors that indicate when the pads are worn.

The drum brake consists of:

• brake shoes;
• brake drums;
• wheel cylinders;
• brake hardware.

Electronic safety systems.

These systems help the driver of the motor vehicle in critical situations:

• the ABS system prevents the wheels from locking during braking;
• the ASR system prevents wheelspin at the drive wheels during acceleration, particularly when pulling away or on surfaces with low grip;
• the ESP system intervenes when the vehicle shows a tendency to skid, helping to maintain the driver's intended path.

Components of the braking system:

• brake pedal – allows the driver to apply the brakes;
• brake master cylinder: receives the force applied to the brake pedal and converts it into hydraulic pressure. This pressure is transmitted through pipes and hoses to the callipers, where it acts on the pistons that press the pads against the brake discs;
• disc brake: is widely used in automobiles due to its consistent braking performance and good cooling capacity. Brake discs, usually made of cast iron, may be ventilated, particularly on the front axle, to dissipate the heat generated during repeated or heavy braking more effectively, such as when descending long slopes or frequently alternating between acceleration and braking;
• brake servo: amplifies the force applied to the brake pedal. When the pedal is pressed, the force exerted is amplified by the brake servo's internal mechanism;
• drum brake: has poorer thermal performance than a disc brake because it dissipates heat less effectively. At high temperatures, expansion of the drum can reduce braking effectiveness.