6.6. Brake mechanism of a forward wheel

Description of the device

Fig. 6.3. Brake mechanism of a forward wheel: 1 – cylinder; 2 – valve of production of air; 3 – the ring is sealing; 4 – brake shoes; 5 – support; 6 – the finger directing; 7 – guide of blocks; 8 – brake disk; 9 – brake board; 10 – piston


Brake of a forward wheel – disk, with automatic adjustment of a gap between blocks and a disk, with a floating bracket. The mobile bracket is formed by a support of 5 (fig. 6.3) and the wheel cylinder 1 which are pulled together with bolts. The guide of 7 blocks fastens bolts to a rotary fist of a wheel. The mobile bracket fastens bolts to the directing fingers 6 which are established in openings of a guide of blocks. In these openings lubricant is put. Between fingers and a guide of blocks rubber covers are established. To grooves of a guide brake shoes 4 are drawn in by springs. In a cavity of the wheel cylinder the piston 10 with a sealing ring 3 is installed. Due to elasticity of this ring the optimum gap between blocks and a disk 8 which surface is protected by a board of a brake 9 is supported. When braking under pressure of liquid the piston 10 presses an internal block to a disk, as a result of reaction force the support 5 moves on fingers 6 and the external block nestles on a disk too. At the same time force of pressing of blocks will be identical. At a disinhibition due to elasticity of a sealing ring the 3rd piston is taken away from a block, and between blocks and a disk the small gap is formed.

Replacement of brake shoes
Minimum admissible thickness of frictional overlays of brake shoes of 1,5 mm. At wear of slips to this thickness, breakage of the drawing-in springs, fragile connection of slips with the basis, oiling of surfaces of slips, in the presence on overlays of deep furrows and chips replace brake shoes new at the same time on both brake mechanisms of forward wheels, i.e. both couples. On a part of cars the control system of wear of brake shoes can be installed. The block with the sensor of wear is from the outer side of a brake disk.

       PREVENTION
At installation of old blocks it is impossible to interchange the position of internal and external blocks or to rearrange them with left on the right wheel and vice versa. It can lead to uneven braking.

1. Slow down the car the parking brake and establish an emphasis under back wheels.
2. Remove the corresponding wheel and clear the brake mechanism of dirt.
3. Pump out a part of liquid from a tank if the level of brake fluid is in a tank on a tag of MAX or gets closer to her.

Fig. 6.4. Bracket of a forward brake: 1 – cylinder; 2 – the ring is sealing; 3 – piston; 4 – boot; 5 – the ring is lock; 6 – brake shoe; 7 – guide of blocks; 8 – support; 9 – the cover is protective; 10 – the finger directing; 11 – the washer is lock; 12 – a bolt of fastening of the directing finger; 13 – a bolt of fastening of the cylinder to a support; 14 – washer; 15 – valve cap; 16 – valve of production of air


4. Unbend a corner of a lock washer of 11 (fig. 6.4) from a side of the lower bolt 12 and turn off a bolt, holding a key for a hexagon the directing finger from a provorachivaniye.
5. Turn a support 8 concerning other finger up.
6. Take out a brake shoe 6 from the piston and lower a support into place.
7. Carefully, not to damage a protective boot 4 and not to allow slopping of brake fluid from a tank of the main cylinder, press through a window in a support the piston as it is possible further in the cylinder, leaning the screw-driver in a brake disk.
8. Lift a support, replace a worn-out external block new and again lower a support into place.
9. Once again press the piston in the cylinder and, having lifted a support, replace an internal brake shoe.
10. Lower a support and wrap a bolt 12, holding a key for a hexagon the directing finger from a provorachivaniye. The carving of a bolt has the covering preventing it a samootvorachivaniye.
11. Record a bolt, having folded a corner of a lock washer.
12. Check and if necessary restore liquid level in a tank of the main cylinder.

       RECOMMENDATION
When replacing blocks check a condition of protective boots of 4 pistons and covers of the directing fingers. Replace the boots and covers torn or lost elasticity. Fill edges of the boots and covers which left seats. After completion of works check a state and fastening of the valve 16, a cap 15 and a hose.
Check and replacement of a brake disk
Minimum admissible thickness of a brake disk is 10,8 mm. If thickness of a disk is less, it needs to be replaced. On a working surface of a brake disk teases and deep risks are not allowed. It is possible to pierce or proshlifovat a disk, but at the same time both parties have to be processed on identical depth, and the final thickness of a disk has to be not less than 10,8 mm.
Check an axial beating of a working surface of a brake disk by means of the indicator, without removing it from the car. It should not exceed 0,15 mm. If the beating is more, replace a disk or its proshlifuyta. At the same time the final thickness of a disk has to be not less admissible.
1. Remove brake shoes.
2. Remove the brake mechanism from a rotary fist, without disconnecting from it a brake hose. Suspend the brake mechanism on a wire to a spring of a forward suspension bracket, watching that the brake hose did not stretch and was not overwound.
3. Turn off two hairpins of fastening and remove a brake disk 8 (see fig. 6.3).
4. Establish a new disk upside-down.

Removal and installation of the brake mechanism
1. Lift and establish a forward part of the car on supports.
2. Remove the corresponding wheel.
3. For convenience of further installation remove brake shoes.
4. Unscrew the union of the pipeline and disconnect a brake hose from the highway. Muffle openings of a hose and a tube not to allow leak of brake fluid.
5. Having turned off two bolts of fastening of a guide of blocks to a rotary fist, remove a guide assembled with a support and the working cylinder.
6. Install the brake mechanism upside-down. After installation restore the level of brake fluid in a tank and pump over a hydraulic actuator for removal of air.

Repair of the wheel cylinder
1. Weaken a tip inhaling a hose on the union of the wheel cylinder 1 (see fig. 6.4).
2. Raskontrite also turn off the top bolt of the 12th fastening of the wheel cylinder to the directing finger, holding the second key for a hexagon the directing finger from a provorachivaniye. Do it carefully not to damage a protective cover 9.
3. Remove a support with the wheel cylinder from a guide of blocks and, holding a key a hose tip for a hexagon, turn off a support from a tip. Be careful, from a hose brake fluid will begin to flow. It is not recommended to unscrew the bolts 13 connecting among themselves a support and the cylinder except cases of replacement of a support or the cylinder.
4. Pay attention, on a tip of a hose the copper sealing ring is established. Replace strongly pressed out ring.
5. Remove a lock ring 5. Then remove a protective boot 4 from the case of the cylinder and the piston.
6. Push out the piston 3 of the cylinder 1, having given a stream of compressed air through an opening for a hose. At the same time not to damage the piston about a surface of a support 8, previously establish wooden laying under the piston.
7. Accurately, not to damage a cylinder mirror, take out from the cylinder a sealing ring 2.
8. Turn out from the cylinder case the valve 16 for pumping.
9. Clear all details and attentively check their state.
10. At wear, damage or strong corrosion of a surface of the piston and a mirror of the cylinder replace the piston and the cylinder. From the cylinder case remove corrosion with a wire brush.
11. Check the directing fingers 10 and covers 9. Make sure that on fingers there is no corrosion and damages and they freely move in openings of a guide of blocks. Otherwise replace the directing fingers. Also replace the protective covers torn or lost elasticity.
12. Replace torn, inflated or lost elasticity a sealing ring 2 and a boot 4. It is recommended to replace a ring and a boot new irrespective of their state.
13. Accurately establish a sealing ring in a pro-point.
14. Put on a boot the piston, having inserted its edge into a piston pro-point. Turn a boot inside out.
15. Grease with fresh brake fluid a cylinder mirror with a sealing ring and the piston. Install the piston in the cylinder by effort of hands (without using the tool).
16. Turn out a boot back and fill its external edge in a pro-point on the cylinder.
17. Establish a lock ring 5.
18. Accurately apply graphitic lubricant on a piston end face so that it did not get in the cylinder.
19. Screw the valve of production of air in the cylinder and connect a brake hose.
20. Grease the directing fingers with the 10th UNIOL-1 lubricant and establish them with protective covers in openings of a guide of blocks.
21. Establish on a guide of blocks a support assembled with the cylinder. Apply on bolts of the 13th fastening of a support to fingers sealant (that there was no corrosion of a carving part of connection) and wrap their moment 30-38 N · m (3,1-3,9 kgfs · м). Zakontrite bolts, having folded corners of lock plates.
22. Install the brake mechanism on a rotary fist upside-down. After that restore liquid level in a tank and pump over a hydraulic actuator.