Drum brake mechanism (Audi 100 C4)

On front-wheel drive Audi 100 models with 4-cylinder engines produced before October 92. (not equipped with ABS), the rear axle has drum brakes. In this version of the brake mechanism, two brake shoes are pressed against the inner surface of the drum by the piston of the brake cylinder (it is located between the upper ends of the brake pads). Due to the arrangement of the brake shoes in the drum brake mechanism used in the Audi-100 (Simplex brake mechanism - one brake cylinder with two pistons), one of the two brake shoes acts in a self-amplifying manner. This means that this brake shoe is pressed against the brake drum within certain limits automatically due to the rotation of the wheel, which reduces the force on the pedal. In the Audi-100 (when moving forward) the front brake shoe acts spontaneously. In jargon it is called the primary or active brake shoe. The rear one is called the secondary or passive brake shoe.

Self-adjusting drum brake mechanism

Drum brakes do not need to be adjusted. This task is taken over, unlike disc brakes, by the adjusting mechanics. With increasing wear of the friction coating, the cylinder rods between the brake shoes are extended so that the shoes can press against the drum again. This is ensured by a wedge with a spring drive, which, as the shoes wear out, extends the rods.

[The original article is available on the website: AUDImanual.ru]