19.4. Disks and tyres
At disk or tyre replacement necessarily replace the rubber valve with a nipple.
Tyres and wheel disks (on disk wheels) are the important elements of a design of the car.
Installation and repair of tyres demands the special tool and professional skills. Experts should carry out these works only.
For safety reasons movements it is possible to change tyres only in steams and only on one axis. Less worn out tyres should be put always on forward wheels.
On all wheels it is necessary to establish only radial tyres of the same design, the identical size (with identical length of a circle) and it is desirable with identical drawing of a protector of the tyre. In the presence of drawing of the protector defining a direction of rotation of tyres, on a lateral surface of the tyre arrows-indexes are put. In this case it is necessary to observe a direction of rotation of the tyre strictly. Optimum operational qualities of the tyre, coupling with a wet road covering are thus provided and deterioration and the noise created by the tyre decrease. If the tyre is damaged, as a provisional measure it is possible to establish for a short while the tyre with the direction of rotation opposite to the set.
On the all-wheel drive car, except that, all tyres should be identical model of the same manufacturer. Otherwise вискомуфта because of an arising difference in frequency of rotation of wheels of both axes it is undesirable will increase the share of draught having on a back axis. It can lead to breakage.
Various depth of drawing of a protector of tyres of forward and back wheels, for example as a result of deterioration, is not so important. However it is recommended to establish tyres with большей depth of drawing of a protector on forward wheels: if tyres of forward wheels are worn out more than tyres back, the length of their circle is less and consequently they rotate faster. As a result in transmission there are additional pressure, and tyres wear out faster.
At a choice of tyres it is necessary to know their marks.
Fig. 13–2. A wheel: 1 – the tyre; 2 – the valve; 3 – a disk; 4 – a bolt of fastening of wheel M14x1,5x27,5, 120 Н·м; 5 – the lock cylinder; 6 – a decorative cover; 7 – a decorative overlay; 8 – грузики
Fig. 13–3. An arrangement of marks of the tyre
Radial tyres (fig. 13–3) have on sidewallsе tyre covers marks, for example:
195/70 R 15 89 H, where
195 – width of a profile of the tyre, mm;
70 – the relation of height of a profile of the tyre to its width, %;
R – an arrangement of threads of a cord of a skeleton – a designation of the radial tyre;
15 – diameter of a rim of a disk, in inches;
89 – an index admissible gruzopodem-nosti tyres;
H – an index of speed, km/h.
Speeds speed, km/h
V 2 40
The date of issue is specified also on sidewallsе tyres (on occasion only on an internal surface of the tyre).
DOT CUL UM8–507 TUBELESS, where
DOT – the manufacturer;
CU – a code designation of the manufacturer;
L2 – The size of the tyre;
UM8 – Tyre type;
507 – manufacturing date (50th week 1997);
TUBELESS – бескамерная the tyre (TUBETYPE – chamber).
Wheel disks too are marked.
For example, the designation 6J х 16 is deciphered as follows:
6J – width of a disk, in inches;
J – height of an onboard edge of a disk;
х – a deep disk;
16 – landing diameter of a disk, in inches.