10.2. Disk brakes

PREVENTIONS
Surely replace all blocks on one axis of the car even if only one is worn-out. If old brake shoes establish again, before removal they need to be marked.
Work with brake mechanisms of each wheel in turn, in case of need the brake mechanism in assembled form on other wheel will carry out an original role.
Remember that during the work of brake shoes dust from their attrition which contains asbestos, unhealthy is formed.


Replacement of brake shoes
Uncover a tank of the brake system and merge about 1 l of brake fluid.
Weaken bolts of fastening of forward wheels, lift a forward part of the car, reliably fix on supports and remove forward wheels.

Fig. 10.2. Forward disk brake mechanism and rotary fist: 1 – bolt and nut; 2 – rotary fist; 3 – nut; 4 – protection cover of a forward brake; 5 – knot of a nave of a forward wheel; 6 – brake disk; 7 – nave nuts; 8 – external brake shoe; 9 – support; 10 – bolt and nut; 11 – bolts of fastening of a support; 12 – hollow bolt of fastening of a brake hose; 13 – plug; 14 – rubber cap; 15 – the union for removal of air; 16 – the directing finger; 17 – dustproof cover; 18 – consolidation of the piston; 19 – piston; 20 – dustproof consolidation; 21 – clamp


Turn out two bolts of fastening of a support (fig. 10.2).
Turn a support up, having taken away it from a brake disk. Support a support by hands or fix it by a twine or a wire on a suspension bracket rack that it did not hang on a brake hose.
The screw-driver remove the fixing brackets and remove an external brake shoe. Take noise-insulating laying from a reverse side of a brake shoe.
Remove an internal brake shoe, having lifted it from a support, and take out noise-insulating laying.
Examine a support cover, carefully turning off edges of a cover, and check lack of leak of liquid. If leak is found, remove a support for capital repairs or replacement.
Press the With-shaped clamp the piston against the stop into a support.

Fig. 10.3. The provision of installation of noise-insulating laying on brake shoes: and – the removed ledges; b – the tag specifying the right or left side; with – the direction of rotation of a brake disk


Establish noise-insulating laying on new brake shoes (fig. 10.3).
Correctly arrange an internal brake shoe and latch it on the piston.
Insert an external brake shoe and latch it in a support.
Lower a support into place.
Screw bolts of fastening of a support and tighten them the required moment.
Several times press a brake pedal that brake shoes were established with a certain gap in relation to a brake disk, then fill a tank with brake fluid.
Establish wheels and lower the car. Tighten nuts of fastening of wheels the required moment.
Avoid sharp braking as far as it is possible, on the first several hundred kilometers of a run of the car until new blocks get used completely.

Removal and installation of a support
Removal
If it is necessary to remove a support from the car, uncover a tank of the brake system and pump out 2/3 volumes of liquid.
Weaken nuts of fastening of a forward wheel, lift a forward part of the car, reliably fix on supports and remove forward wheels.
If it is necessary to remove a support from the car, turn off a hollow bolt of fastening of a brake hose to a support.
Turn out two bolts and remove a support from the car. If there is no need to remove a support from the car, fix it by a twine or a wire on a suspension bracket rack that the support did not hang on a brake hose.
Installation
Examine bolts on existence of excessive corrosion and rubber plugs and covers on existence of gaps and damages, replacing them new in case of need. Before installation grease contact surfaces of bolts and plugs with lubricant on a lithium basis, clear covers.
Correctly arrange a support in relation to a brake disk and a rotary fist and fix by bolts, having tightened them the required moment.
Connect a brake hose (if he acted) and screw a hollow bolt. If the brake hose was disconnected from a support, remove air from the hydraulic drive of the brake system.
Make sure that at turn of a forward wheel from one extreme situation in another the brake hose does not adjoin to elements of a forward suspension bracket and a body.
Establish wheels and lower the car on the earth. Tighten nuts of fastening of a wheel.
If removal of air from the hydraulic drive of the brake system is not required, several times press a brake pedal that brake shoes were established with a certain gap in relation to a brake disk.
Check the level of brake fluid, in case of need fill it.

PREVENTION
Previously get a repair kit of a brake support for your model of the car.

Repair of a support
Remove a support and brake shoes. There are two methods of extraction of the piston from a support. At the connected brake hose and the removed brake shoes the piston can be pushed out, using the hydraulic pressure of brake fluid and having established wooden whetstone instead of brake shoes. Observe precautionary measures that your fingers did not get between the piston and a support. The assistant has to press very slowly a brake pedal for pushing out of the piston outside, and you be prepared for a pressure of brake fluid at a piston exit.
Clear an external part of a support brake fluid, the denatured alcohol or by means of installation for cleaning of the brake system (never use gasoline or kerosene), then place a support on a pure workbench.
Turn out the union for removal of air.
If the piston was not removed, take it from a support for what give air under low pressure to the brake cylinder through an opening for connection of a brake hose, having established wooden whetstone instead of brake shoes. Use the air pressure sufficient only for pushing out of the piston from an opening. If the piston takes off with big effort even if wooden whetstone remains on the place, then the piston can be damaged.

PREVENTION
When using compressed air for extraction of the piston never you keep fingers in front of the piston in attempt to catch or protect it, it is so possible to suffer a serious injury.

Remove a clamp and dustproof consolidation from a support piston opening.
Using the wooden or plastic tool, take out consolidation of the piston from a flute in the support cylinder. Use of metal tools can lead to damage of the cylinder of a support.
Remove the dustproof covers directing fingers and plugs from support ears.
Clear the remained details brake fluid. Wait until all brake fluid flows down, and then vigorously stir up details to remove as much as possible liquid.
Carefully investigate the piston and the cylinder of a support on existence of notches, zadir, traces of corrosion and attritions. If defects of a surface are found, replace details. Processing of the cylinder of a support by a fine-grained emery paper for removal of traces of easy corrosion and spots is allowed. Examine bolts, pins and plugs on existence of traces of corrosion and damages, as required replace worn-out details.
At assembly grease an opening of the piston and consolidation with pure brake fluid. Impose lubricant of red color from a repair kit on consolidation of the piston.
Establish consolidation in a support cylinder flute.
Put on dustproof consolidation the piston. Apply a part of lubricant of orange color from a repair kit on dustproof consolidation, then install the piston and dustproof consolidation in the support cylinder. Establish a clamp of dustproof consolidation.
Screw in a support the union for removal of air.

Fig. 10.4. Places of lubricant of covers, guides of fingers and pins of a support


Grease the dustproof covers directing fingers and pins lubricant of orange color and establish in a support (fig. 10.4).
Apply a small layer of lubricant on laying of a brake shoe (number 817 549 248 according to the Mazda specification) or special noise-insulating structure. Do not allow hit of lubricant on the surface of friction. Establish brake shoes.
Establish a support and remove air from the hydraulic drive of the brake system.

Brake disk
Lift the car and reliably fix on supports.
Remove a wheel.
Remove knot of a brake support.

PREVENTIONS
There is no need to remove a support from the car therefore after a reversing of bolts of fastening of a support fix it by a twine or a wire on a suspension bracket rack. Do not suspend a support on a brake hose as it can cause damages of a hose.
If replacement of a brake disk is necessary, replace both for ensuring uniformity of braking. When replacing brake disks it is necessary to replace also brake shoes.

Slowly turning a brake disk, visually check its state from two parties. Wear of a brake disk from blocks has to be in admissible limits. If on a disk there are cracks, replace a disk.

Fig. 10.5. Use of the indicator of hour type for measurement of a beating of a brake disk


The indicator of hour type check a beating of a brake disk (fig. 10.5). Fix the indicator in any convenient place and, turning a brake disk, define its beating at small distance from the outer edge. Before check of a beating of a brake disk be convinced that the hug bearing in technically working order. If the beating exceeds the most admissible and the bearing is serviceable, remove also to a pereshlifuyta a brake disk. Some workshops can pereshlifovat a brake disk without removal from the car.
Check a brake disk for existence of cracks, especially around openings under bolts of fastening of a wheel, and also on existence of wear or mechanical damages, if necessary replace it.
Measure thickness of a brake disk in several points. Because on perimeter of a brake disk there is a step, at measurement of thickness of a brake disk with use of a caliper enclose two coins under its sponges. For determination of true thickness of a brake disk subtract thickness of two coins from the indication of a caliper.

Fig. 10.6. Measurement of thickness of a brake disk with use of a micrometer


It is possible to measure thickness of a brake disk with use of a micrometer (fig. 10.6) more precisely.
If fluctuations of thickness of a brake disk exceed 0,127 mm, when braking there can be pulsations. If thickness of a brake disk is still sufficient, remove also to a pereshlifuyta a brake disk.
For removal of a brake disk from a nave it is necessary to use special tools and techniques therefore it is necessary to remove a nave with a brake disk and to deliver it to service station for processing or replacement.