The brake pedal is of a suspended type, fixed on the same axis as the clutch pedal, rotates in two plastic bushings, and is equipped with a return spring. Above the pedal is a brake light switch; its contacts close when the pedal is pressed. The brake pedal free play should be 3–5 mm (adjustment see section Removing the vacuum brake booster and adjusting the free play of the brake pedal).
To reduce the effort on the brake pedal, a vacuum booster is used, using the vacuum in the intake manifold of a running engine. It is located between the pedal pusher and the brake master cylinder and is attached with nuts to a bracket on the front shield in the engine compartment. Amplifier - non-separable, in case of failure it is replaced (amplifier - from VAZ-2108). The simplest check: on a car with an idle engine, press the brake pedal several times and, keeping the pedal depressed, start the engine. With a working amplifier, after starting the engine, the pedal should go forward. Remember that a failure or insufficient efficiency of the vacuum booster can also be caused by a leak in the hose that takes vacuum from the intake manifold.
The main brake cylinder is attached to the vacuum booster housing with two studs. Hoses are put on the fittings in the upper part of the cylinder, through which fluid from the brake reservoir is supplied to the cylinder. The tank is marked with maximum and minimum liquid levels, and a signal device with a float is mounted in the lid, which closes the contacts when the liquid level drops. The screws at the bottom of the cylinder limit the movement of the pistons. The screws are sealed with copper or aluminum gaskets. In front of the cylinder (along the car) a plug is screwed in, which serves as a stop for the return spring and is also sealed with a copper or aluminum gasket. Fittings for brake pipes are screwed into the holes on the sides of the cylinder: into the front holes - a circuit that supplies fluid to the front wheels, into the rear holes - to all wheels.
The brake mechanisms of the front wheels are disc, with a three-piston floating caliper. The upper piston is driven from one circuit (together with the pistons of the working cylinders of the rear wheels), the two lower ones are from the other. The cylinder block is fixed in the caliper on two guides and fixed with a spring-loaded lock. Between the cylinder block and the caliper there are pads: the inner one rests on the cylinder pistons, the outer one - on the caliper tide. The caliper can move in the shoe guide, being pressed against it by two spring-loaded levers. The shoe guide is rigidly attached with two bolts to the steering knuckle. From unscrewing, the bolts are fixed by the edges of the protective cover (they are bent on the verge of the bolts after tightening).
Brake discs are cast iron. Minimum disc thickness at wear 9.5 mm, maximum allowable runout (on the largest radius) - 0.15 mm. The minimum allowable thickness of the front brake pads is 1.5 mm.
The brakes of the rear wheels are drum, with two-piston wheel cylinders and automatic adjustment of the gap between the pads and the drum. The automatic clearance adjustment device is located in the wheel cylinder and consists of two elastic steel split rings (one for each piston), mounted on pistons with an axial clearance of 1.25–1.65 mm.
The elasticity of the ring is selected in such a way that it does not move along the cylinder surface from the force of the coupling springs of the pads (but only from the effort of the pistons). As the pads wear, the pistons move the rings through the cylinders during braking, maintaining a constant calculated clearance between the pads and the drum. In case of damage to the piston mirror due to mechanical impurities in the brake fluid or corrosion, the rings and pistons may «turn sour» in the cylinder, losing mobility. In this case, it is necessary to replace the cylinders and brake fluid.
Brake drums - aluminum, with cast iron rings (working surface). The nominal inner diameter of the drum is 250 mm. It is allowed to turn the drums when worn. Largest allowable diameter (when worn or after turning) - 251 mm.
The pressure regulator serves to reduce the braking force on the rear axle, which prevents the car from skidding when braking. It limits the pressure in the rear brake mechanisms depending on the position of the rear of the body relative to the road: with an increase in the load on the rear axle, when the grip of the rear wheels improves, the regulator provides more pressure in the wheel cylinders and vice versa, with a decrease in load, the pressure drops. The regulator is attached with two bolts to the bracket in the right rear of the body and is driven by an elastic lever attached through a rod to the rear axle beam. With an increase in the load on the rear axle of the car, the elastic lever is also loaded, transferring force to the regulator piston. When the brake pedal is pressed, the fluid pressure tends to push the piston outward, which is prevented by the force from the lever. When the system comes into equilibrium, a valve located in the regulator isolates the rear brake cylinders from the master brake, preventing further increase in braking force on the rear axle. Due to the ovality of the holes in the bracket, the regulator can be rotated, changing its position relative to the lever (see Checking the performance and adjusting the drive of the rear brake pressure regulator). To extend the life of the regulator, put 5–6 g of DT-1 lubricant into the protective rubber cap (or graphite), it also covers the axis through which the lever passes, and the protruding part of the piston. It is not recommended to disassemble the pressure regulator; if it fails, it is replaced.
The drive of the parking brake system is mechanical, cable, on the rear wheels. It consists of a lever, a front cable with a threaded end (with sleeve and two nuts), retractable spring, rear cable, its guide, two levers and two spacer bars - one each (one) for each brake. The drive is adjusted by moving the nuts on the threaded end of the front cable (after adjusting the nuts are locked). The full stroke of the lever after adjustment should correspond to a rise of 4-5 teeth in the sector.