Front disc brake pads - check
The brake pads of the front disc brakes are usually enough for a run of 50,000 km. However, we recommend that you do not neglect the regular visual inspection of their condition. The permissible residual thickness of the brake linings is 2 mm. The thickness of the supporting metal plate on which the overlay is attached is not taken into account. This plate is about 5 mm thick. Visual inspection of the thickness of the pads is carried out with the wheel cover removed.
1. Light the brake pads with a flashlight through the hole in the rim and evaluate the condition and thickness of the brake pads. More accurate is the control of the brake pads on the removed wheels.
2. Measure the thickness of the inner and outer brake pads with a ruler.
When removing the wheels to check the condition of the brake pads, the brake discs should also be checked at the same time
On the surface of the brake discs there should be no grooves formed as a result of friction due to contamination. These grooves lead to premature wear of new brake linings and reduce braking efficiency. Grooved brake discs can be refinished by grinding if they are not worn and their thickness allows this. The blue color of the brake disc metal can be ignored.
Replace brake discs on both wheels at the same time. Replacing the brake disc on only one wheel can result in uneven braking of the wheels.
When replacing the brake pads, the brake pads of both wheel brakes must be replaced.
Checking the condition of the brake pads of the disc mechanism of the rear wheels is carried out in the same way as for the front wheels. The residual thickness of the brake linings, excluding base plates, must not be less than 2 mm.
Brake pads rear drum brakes - check
When determining the residual thickness of the brake linings of the rear drum brakes, only the thickness of the front pad is measured, because it wears out to a greater extent.
3. Place the rear of the vehicle on jack stands.
4. Remove the plastic cap from the corresponding rear wheel.
5. Shine a flashlight into the viewing hole in the caliper body. The remaining thickness of the brake pads without backing plate must be at least 2.5 mm.
Free travel of the brake pedal - check
6. Press the brake pedal by hand. The pedal free play should be a maximum of ⅓ of the possible pedal travel. A longer free play means that the pads have worn down to the maximum allowable thickness and must be replaced.
Extended brake pedal travel can also be caused by sticky brake pads or calipers. The ingress of air into the brake system also leads to an increase in the free play of the brake pedal.
Parking brake lever free travel - check
The action of the parking brake should occur when the parking brake lever is set to the third tooth of the sector. When tightening the parking brake lever on the fourth tooth of the sector, the rear brakes should be locked.
On vehicles with rear disc brakes, the amount of idle travel of the parking brake lever depends on the functioning of the adjusting mechanism. However, in general, you can be guided by the following rule. If the parking brake lever travel is increased, then this is evidence of wear on the rear brake pads or the result of stretching of the drive cables.
As a rule, adjustment of the parking brake is only necessary when replacing the cable or rear brake pads.
Vacuum brake booster - check
7. Stop the engine.
8. Depress the brake pedal 10 times.
9. Leave the brake pedal depressed and start the engine. If the vacuum brake booster is normal, then the brake pedal will move down a little more when the engine is running. If this does not happen, then the vacuum booster is faulty. The most likely cause of the defect is a leak in the low pressure air supply hose from the intake manifold, a malfunction of the check valve on the low pressure hose, wear of the rubber sealing ring between the main brake cylinder and the vacuum booster or the vacuum booster cuff.
Brake Fluid - Change
The moisture absorbed by the brake fluid not only lowers its boiling point, but also leads to corrosion of the brake cylinders and pipelines. For this reason, the maintenance plan calls for changing the brake fluid every two years.
To replace the brake fluid, you need two liters of fresh.
10. Drain all the brake fluid from the expansion tank, taking it with a siphon or an old oiler. As soon as all the liquid from the expansion tank has been drained in this way, fill the tank with new one.
11. Bleed the system until fresh brake fluid comes out of the bleeder port. To ensure complete removal of used brake fluid, drain 500 cm3 of brake fluid from each bleeder when bleeding.
Bleeding order: rear right, rear left, front right, and last front left.
Tire condition check
The condition check is best performed when the vehicle is jacked up, such as when changing the oil at a gas station.
12. Rotate each wheel completely.
13. Use a small screwdriver to remove any foreign bodies caught in the tread profile. Be careful not to damage the protector.
The tire tread pattern, in accordance with regulations, must have a depth of at least 1.6 mm across the entire width of the tire.
Elevations in the tread groove are used to check wear. They are marked on the side of the tire with the letters TW1 (tire wear indicator).
When these marks are at the same height with the ribs of the tread pattern, this means that the value of the residual profile is 1.6 mm, and the tire needs to be changed.
The wear pattern of the tire tread can be used to judge whether the tire is being used correctly and whether the wheel is properly balanced.
Wear on the outside of the front tires is normal. The reason for this is the increased stress on these areas of the tire surface when cornering.
One-sided profile wear indicates incorrect wheel alignment.
Strong wear in the middle of the profile indicates increased air pressure in the tires.
Strong wear on the outer sides of the profile indicates that the car has been operated for a long time with insufficient air pressure in the tires.
Uniform «bald spots» in the tire profile indicate a malfunction of the suspension strut.
Uneven wear in certain areas of the tread indicates wheel imbalance or a defect in the tire carcass.
If there is a place on the tread with a heavily worn pattern, then this is the result of braking with a locked wheel (only on vehicles without ABS).
Note. When dismantling a balanced wheel to perform any work, it is recommended to first mark its position on the hub. Subsequently, the wheel can be installed in its original place and its balancing is not required.
Wheel replacement
On the road, changing a wheel can be a problem, especially if the wheel bolts are rusty. Use a piece of pipe as a lever to increase the force when loosening the bolts.
14. Apply the parking brake and engage 1st gear or reverse.
15. Turn on the hazard warning lights and place a warning triangle on the road.
16. Place stones or pieces of wood under the wheels on the opposite side of the car to prevent rolling
17. Remove the cap.
18. Unscrew the wheel bolts one turn.
19. Install a car jack under the mark on the edge of the body and raise the car.
20. Completely unscrew the mounting bolts.
21. Remove «let down» wheel and install the spare.
22. Apply a light coat of grease or oil to the tapered surfaces of the bolts and to their threads and tighten the bolts evenly in a criss-cross pattern. At the same time, turn the wheel back and forth to ensure that the wheel is centered on the hub.
23. Lower the machine and tighten the bolts with a torque of 110 Nm.
24. Put on the cap. Remember to insert the tire nipple into the slot on the cap.
After changing the wheel, after driving a few kilometers, you should check the correct tightening of the bolts.
Wheel balancing
Wheel imbalance is felt by the vibration of the steering wheel or the front of the car. Both types of vibration occur only at a certain speed of movement. The reason is the uneven distribution of mass around the circumference of the wheel. Therefore, the wheels must be statically and dynamically balanced. There are two methods for this purpose.
- The wheel is removed from the car and installed on a balancing machine. Turn on the machine to determine the imbalance, eliminated with the help of lead weights.
- Precise wheel balancing is carried out on a special stand. This compensates for the imbalance of the wheel hub and the brake disc. The wheels of front-wheel drive vehicles are driven from the engine to the required rotational speed to determine the residual imbalance, which is also eliminated with the help of lead weights.
As for all-wheel drive vehicles, they are mounted on goats so that all wheels rotate freely.
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