- remove the rubber protective cap;
- unscrew the cap-key of the pumping valve;
- moisten the valve slightly and make sure. that there are no air bubbles. If an air bubble forms at the same time, then this indicates an air leak through the spool:
- turn the cap-key over and wrap the pumping valve spool with it;
- re-check the tightness of the valve. If the valve leaks air, it must be replaced;
- Be sure to install the protective cap.
All tires have a built-in wear indicator in the form of control strips, which are exposed when the tread depth drops to 1.6 mm. after which the tires are considered worn (arrow, fig. 2.25)
The optimal tire tread depth is 3.0 mm or more, for winter tires - 4.0 mm or more. Winter tire performance («M+S») on snow, mud and slush falls already at a tread depth of 4 mm.
Control strips are located around the entire circumference of the tire where there are marks «TWI» (Tread Wear Indicator). Tire wear must be checked in several places («TWI») at the same time, because Tire wear depends on many factors.
By the nature of the wear of the tread, it is possible to determine the cause that caused it, fig. 2.26.
So on the bus (1) shows wear caused by prolonged driving with high pressure, and the tire (2) - with insufficient pressure. Tire wear (3) with characteristic rounded edges on one side of the tread pattern and sharp edges on the other side, is caused by wheel alignment problems. For deep deviations (10-15 mm) recommended toe-in, tires may be worn out after driving less than 1,000 km. Tire (4) has uneven tread wear due to a violation of the camber of the wheels. This is especially pronounced with a large difference in the collapse of the left and right wheels. Type of wear (5) as one or two «bald head», is a consequence of increased runout of the brake disc or drum. This «bald heads» may be accompanied by the same diametrically «baldness», if the brake drum of the parking brake has increased ovality or lateral runout of the brake disc. Less pronounced «bald head» appears as a result of emergency braking at high speed when driving on a concrete road.
On the bus (6) patchy wear is visible, resulting from large angular oscillations of the front wheels or one wheel.
The main causes of patchy tire wear are:
- play in the joints of the steering rods;
- malfunction of the front shock absorbers or one of them;
- fuboe imbalance of wheels;
- loose steering gear.
Damaged wheels are not repaired, they are replaced with new ones, which increases safety.
Pay special attention to the absence of punctures and cuts on the tires. If cuts reach the carcass of the tire, it must be replaced.
It is recommended to replace tires, including the spare wheel, at least once every 6 years, even if the tires have a 10-year shelf life. Balancing should be carried out every time a tire or wheel is changed. The tire pressure of the spare wheel must be 0.5 bar higher than the maximum prescribed value indicated on the plate (see fig. 1.58) are located on the end of the driver's door.
Install the wheel bolts dry and tighten crosswise with a torque of 140±10 N.m (14.0±1.0 kgf·m).
Note. For safety reasons, the vehicle must only be fitted with tires of the same type and with the same tread pattern.