During repairs, brake pads and wheel cylinders or parts included in them are usually subject to replacement, for the removal of which it is not necessary to completely remove the brake mechanisms
Fig. 1 front wheel brake
Remove the complete brake mechanisms from the car only when they are completely replaced with new ones or when the axles are completely disassembled.
When installing the front wheel brakes on the car, pay attention to the correct position of the shield.
The upper cylinder should be tilted forward (from the vertical axis) at an angle of about 30° (on vehicles with axles with final drives, the cylinders are horizontal).
When braking, the pads should be pressed out in the direction of rotation of the brake drum when the car moves forward.
When installing the brake mechanisms of the rear wheels on the car, the block with a long pad should be in front.
Fig. 2. Rear wheel brake
Remove and install brake pads in the following order:
1. Jack up the car and remove the wheel whose brake pads need to be removed.
2. Remove the brake drum from the hub. To do this, unscrew the three screws securing the drum to the hub.
If the drum is difficult to remove, then wrap the removable bolts in the three special threaded holes in the disc, and, evenly wrapping them, remove the drum.
Fig. 3. Removal and installation of the brake shoe return spring
3. Remove the brake shoe return spring using special pliers (fig. 3).
4. Remove the top release spring cups, springs, lower cups and remove the pins.
5. Turn away nuts of basic fingers, take out basic fingers, eccentrics and remove brake pads. Install the pads with new linings and assemble the brake mechanisms in the reverse order.
The brake drums are machined with the hubs, so install them on the same hubs after removal.
Swapping brake drums from one hub to another will increase the runout of the working surfaces of the drum relative to the brake linings.
When installing the drum in place, before tightening the screws, firmly press the brake drum against the hub with the wheel nuts and only then tighten the screws. This is necessary for a tighter pressing of the brake drum to the wheel hub.
Adjust the brake pads in the following order:
1. Jack up the wheel whose brakes need to be adjusted.
2. Slightly unscrew the nuts of the support pins and set the support pins to their original position (the marks on the ends of the support pins should be located as shown in Fig. 1 and 2).
Fig. 4. Adjusting the brake pads of the rear wheel with support pins
3. While pressing the pedal with a constant force of 118–147 N (12–15 kgf), turn the support fingers so that the ends of the shoes on the side of the fingers rest against the brake drum (Fig. 4).
Determine the moment of contact between the pads and the drum by the increase in resistance when the support pin is turned. In this position, tighten the support pin nuts, being careful not to turn the pins.
4. Turn the adjusting eccentrics until the shoes hit the brake drum until the wheel brakes.
5. Having stopped pressing the pedal, turn the adjusting eccentrics in the opposite direction so that the wheels rotate freely, without hitting the drum on the blocks.
When new pads with unworn brake drums are properly installed, the “a” marks on the support pins should be located as shown in fig. 1 and 2 or with deviations from this position in one direction or another up to 50 °.
When installing new pads, when the friction linings have not yet been run in to the surface of the drums, the brake drums may heat up a little after the specified adjustment.
After a few brakings, the pads will run in and the heating will stop.
If the brake drums become very hot, move the pads slightly away from the brake drum adjusting eccentrics.
Remove and disassemble wheel brake cylinders in the following order:
1. Disconnect the pipeline from the cylinder and remove the cylinder.
2. Remove the protective caps of the cylinders, take out the pistons with sealing rings and springs.
Assemble and install wheel brake cylinders in reverse order.