The brake mechanisms of the front wheels are disc, with a single-piston floating caliper (when braking, the piston presses the inner pad against the disc, and the caliper, moving in the opposite direction, presses the outer pad).
The minimum allowable thickness of the front brake pads when worn is 3 mm.
The discs are ventilated, mounted on the hubs and attached to them with wheel bolts.
The minimum allowable disc thickness when worn is 19 mm.
The bracket is attached with two bolts to the steering knuckle.
The brake cylinder is made in the caliper housing; on the outside, it is covered with a rubber boot (dust boot) to protect it from dirt.
Inside the cylinder there is a groove into which an o-ring (cuff) is inserted.
When the piston moves out of the cylinder during braking, this ring twists slightly and, after braking, tends to return the piston to its original position.
This maintains a constant minimum clearance between discs and brake pads. The cylinder has a bleed valve.
The front brake mechanism is shown in Figure 1
Replacing brake pads
- 1. Apply the parking brake.
- 2. Install support bars under the rear wheels.
- 3. Loosen the front wheel mounting bolts.
- 4. Raise and support the front of the car.
- 5. Remove wheel.
- 6. Rinse the brake with warm water and dry. Do not use gasoline, diesel fuel or any other mineral solvents to clean the brakes.
- 7. Check the wear of the brake pads through the hole in the caliper housing. If the pad friction lining thickness is less than 3 mm, the pads must be replaced on both sides of the vehicle.
- 8. Unscrew the lower bolt of the bracket housing, while holding the guide pin with a wrench.
- 9. Rotate the brace body up around the axis of the upper pin.
Mark the brake pads if the old pads are to be installed again, since it is unacceptable to replace the inner and outer pads with each other, as well as between the left and right wheels. This can lead to uneven braking.
Remove the brake pads.
11. Clean the brake parts from dirt and rust, especially the seats of the brake pads.
Do not use gasoline, diesel fuel or any other mineral solvents to clean the brakes.
12. If new brake pads are installed, the piston must be carefully pressed into the cylinder. At the same time, make sure that the piston does not warp.
- 13. Place the brake pads on the caliper base, making sure that the pressure springs are vertically up and parallel to the top edge of the brake pads.
Old pads are installed in accordance with the previously made markings.
- 14. Lower the brace body.
- 15. Tighten the lower mounting bolt to a torque of 32–39 Nm (3.2–3.9 kgf m), while holding the guide pin with a wrench.
- 16. Press the brake pedal several times to set the piston to its working position.
- 17. Install the front wheel and tighten the mounting bolts.
- 18. Lower the vehicle to the ground and tighten the wheel bolts evenly diagonally to 100–120 Nm (10.0–12.0 kgf m).
- 19. Check the brake fluid level in the reservoir and top up if necessary.
- Clean the brake disc.
- Measure the thickness of the disc with a caliper. The minimum allowable disc thickness is 19 mm. If the thickness of the disc is less than acceptable, the disc must be replaced.
When available At any risk, the disc can be removed and polished, but taking into account that its final thickness is not less than acceptable.
It is recommended to replace the brake discs on both sides.
- - Unscrew the two mounting bolts, remove the brake caliper assembly and hang it on the wire to the body, making sure that the brake hose is not twisted and does not experience excessive stress.
- - Remove the brake disc.
Install the brake disc in the reverse order of removal.
Before installing, clean the mating surfaces of the wheel hub and brake disc.
Tighten the two brake caliper mounting bolts to a torque of 32–39 Nm (3.2–3.9 kgfm). After installation, press the brake pedal several times to set the piston to its working position.
Remove the bolt 1 of the holder 2 of the brake hose end.
Unscrew the connecting bolt 3, disconnect the tip 4 of the brake hose from the bracket and plug the hole in the brake hose.
Unscrew the two bolts 5 securing the bracket body to its base, while holding the guide pins 6 with a wrench, and remove the bracket body.
1. Remove the heat-insulating gasket from the piston, if it is provided for installation according to the configuration.
2. Remove protective cover 1 of the piston. Clamp the body of the clamp in a vice with soft metal jaws.
Remove piston 2 from the cylinder by blowing compressed air through the brake hose fitting while holding the piston with your hand.
3. Remove the O-ring from the cylinder using a wooden spatula.
The use of metal objects is not recommended, as this may damage the cylinder groove under the sealing ring.
- 4. Unscrew the bleed valve.
- 5. Flush the piston and cylinder with fresh brake fluid.
1. Inspect the working surfaces of the piston and cylinder.
If there are signs of wear, corrosion, cavities and nicks on the working surfaces of the piston and cylinder, replace the bracket body complete with the piston.
- 1. Lubricate the inner surface of the cylinder with new brake fluid.
- 2. Lubricate the new O-ring with new brake fluid and insert into the cylinder bore.
- 3. Lubricate the new protective cover with new brake fluid and insert it into the groove on the piston.
- 4. Insert the piston into the cylinder with the force of your fingers, without using any tool, and using a screwdriver, carefully insert the outer edge of the protective cover into the groove of the cylinder.
- 5. Lubricate the bleed valve with fresh brake fluid and screw it into the caliper body.
- 6. Install a heat-insulating gasket on the piston, if it is provided for installation according to the configuration.
Install the bracket body in the reverse order of removal. At the same time, tighten the two bolts securing the bracket body with a torque of 32–39 Nm (3.2–3.9 kgcm), while holding the guide pin with a wrench.
Be sure to replace the copper o-rings on the brake hose end. After installation, bleed the repaired brake.