Brake Operating Principle

When you press the brake pedal, the pushrod connected to the pedal presses two pistons located one behind the other in the brake master cylinder (located in the engine compartment).

The pistons force the brake fluid out of the master cylinder. The resulting pressure in the brake system is transmitted through the brake lines to the wheel cylinders.

In the wheel brakes, the pistons press the brake pads against the brake discs.

On the rear wheels of Audi 80 vehicles with 66 kW engines, built before October 1992 and not equipped with ABS, the brake shoes press against the brake drum. All other versions, as well as the 66 kW version equipped with ABS, have disc brakes at the rear as well as at the front.

Hydraulic pressure is distributed to two independent brake circuits (brake hydraulic circuits), namely one front wheel and the diagonally opposite rear wheel (diagonal split dual-circuit brake system).

If one brake circuit fails, one front wheel and the rear wheel on the opposite side of the vehicle can still be braked. With the non-braking front wheel, the vehicle can still be steered, and the non-braking rear wheel keeps the rear of the vehicle in line.

The parking brake acts on the rear wheels through a cable system, regardless of whether drum or disc brakes are fitted.

On older front-wheel-drive Audi models with 4- or 5-cylinder engines, an anti-lock braking system (ABS) was available at extra cost. From January 1993, ABS was standard equipment; all-wheel-drive models and versions with 6-cylinder engines were equipped with ABS as standard from the start. For more details on ABS, see the next chapter.

Note: if one brake circuit fails, you will have to press the pedal much harder (and the pedal travel will increase) to achieve braking. The braking distance will also be longer.