Thus, complex structures are indispensable in the braking system, which is why both the front and rear wheels are equipped with disc brakes. C54 and FN3 brakes are used as front wheel brakes, and C38 brakes are used on the rear axle. To improve heat dissipation, the front brake discs are ventilated. The good news for car enthusiasts is that these brakes do not need to be adjusted.
Front ventilated brake discs
Disc brakes are also installed on the rear axle. There is a handbrake cable holder on the brake caliper
In gasoline-powered vehicles, the brake booster uses part of the intake pressure produced by the engine. The handbrake through the cables acts on the rear wheels.
Brake system
The braking system functions as follows. When the brake pedal is depressed, the push rod, which is connected to this pedal, pushes two pistons arranged one behind the other into the brake master cylinder, which is mounted on the brake booster. The pistons transmit the force of the rider's foot to the brake fluid inside the brake master cylinder. As a result, hydraulic pressure is generated, which is transmitted through pipelines and hoses to the wheel brake cylinders. On wheels, pistons press the brake pads against the brake discs.
Technical requirements for the operation of trackless vehicles prescribe that cars must be equipped with two braking systems, which must work independently of each other. The meaning of this prescription is that if one of the systems fails, the car must be braked by the other system.
This requirement can be met with a dual-circuit braking system with diagonal wheel brakes. In this case, each of the brake circuits is responsible for braking one front and one rear wheel, which is diagonally relative to the front wheel, that is, on the other side of the car. If one of the circuits fails, the other front and rear wheel can still be braked by the other circuit. True, in order to achieve the same braking effect as with a working brake system, you have to press harder on the brake pedal. The pedal is pressed further, and the braking distance is significantly increased.
Scheme of the brake system with a diagonal arrangement of brake mechanisms: 1 - left front wheel, 2 - right rear wheel, 3 - right front wheel, 4 - left rear wheel.
Electronic components of the brake system
The Audi A4 is equipped with Bosch 5.7 anti-lock braking system. The anti-lock braking system prevents the wheels from locking during hard braking. The advantage of such a system is that the vehicle remains steerable even under full braking. To this end, the anti-lock braking system distributes the braking force between the individual wheels. Braking with blocking the wheels in its pure form becomes impossible. Malfunctions of the anti-lock braking system do not affect the brake system and the brake booster in any way. The conventional braking system continues to operate without the anti-lock braking system.
Strengthening of braking forces is reached thanks to the vacuum amplifier of a brake drive. Thus, when equipped with an anti-lock braking system, a mechanical brake force regulator is eliminated. A special computer program, in accordance with which the control device operates, ensures the distribution of braking forces on the rear axle. More information can be found in the technical dictionary (see article «Anti-lock braking system in detail»).
The most important parts of the brake system
Dual circuit braking system. Hydraulic system with two brake circuits, each acting on one of the front wheels and on the diagonal rear wheel.
Master brake cylinder. Converts the mechanical force that acts on the brake pedal into hydraulic force. Provides rapid pressure reduction in the system when the brake is released.
Brake booster. Produces approximately 60 percent of the braking force. In gasoline engines, the required reduced pressure is taken from the intake manifold.
Wheel brake cylinders. The brake fluid pressure here reaches 120 bar. Cylinder pistons transmit pressure to the brake pads (brake pads).
Brake disk. Massive steel wheel, on the front axle it is ventilated. The brake disc rotates freely in the airstream along with the corresponding front wheel (removes frictional heat).
Brake caliper. Sits in the form of a saddle on the brake disc. In the case of a so-called floating caliper brake, only one brake piston is needed to press both brake linings against the brake disc.
What happens when braking?
Pressing the brake pedal. The piston in the brake caliper presses both brake linings against the brake disc (inner and outer brake pad).
Releasing the brake pedal. The piston seal moves the piston away from the brake disc, and with it the brake caliper. This creates a gap of less than one millimeter between the brake pad and the disc, and the brake disc begins to rotate freely again.
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