Rear wheel brake mechanism (VAZ-2109)

The rear wheel brake mechanism is a drum type, with automatic adjustment of the gap between the shoes and the drum. It is mounted on the support shield 11 (figure 85), fixed on the flange of the rear suspension arm together with the rear wheel axle. In the lower part of the shield, a pack of plates is fixed with two rivets, one of which is a support for the brake shoes 4. The other plates guide the movement of the lower part of the shoes on the support plate, limiting their axial movement. In the upper part of the shield, the wheel cylinder 6 is fixed with two bolts. The brake shoes are pulled together by the upper 7 and lower 3 springs, which press the shoes against the lower support and against the stops of the pistons of the wheel cylinder. From lateral displacement, the shoes are held: in the lower part by the guide plates of the support, in the upper part - by the grooves of the stops of the pistons of the wheel cylinder, and in the middle - by the guide springs 5, one hook of which is connected to the edge of the shoe, the other - to the pin of the support shield. Due to the non-rigid connection of the shoes with the brake shield, they self-align at the moment of contact with the brake drum, which increases the efficiency of braking and promotes more uniform wear of the shoe linings. A nipple 11 is screwed into the threaded hole of the cylinder (figure 86) for bleeding the brake and a tube fitting for supplying fluid to the cylinder.







The automatic clearance adjustment device is located in the wheel cylinder. Its main element is a split thrust ring 9 (see figure 86), mounted on piston 4 between the flange of thrust screw 10 and two crackers 8 with a gap of 1.25...1.65 mm. The thrust rings are installed in the cylinder with an interference fit that ensures a ring shear force along the cylinder surface of at least 35 kgf, which exceeds the force on the piston from tension springs 3 and 7 (see figure 85) brake pads. When the linings wear out, the gap of 1.25...1.65 mm is completely eliminated, the flange on the stop screw 10 (see figure 86) is pressed against the flange of ring 9, as a result of which the thrust ring shifts after the piston by the amount of wear. When braking stops, the pistons are shifted by the force of the tension springs until the crackers stop against the flange of the thrust ring. In this way, the optimum clearance between the shoes and the drum is maintained.