4.2.2. Description of disks

Repair of a disk with use of welding, heating or forging is not allowed. All damaged disks have to be replaced.

Disks have to be replaced if they are deformed or have an excessive side or radial beating, do not provide tightness of a wheel, have violations of geometry of openings under a bolt, do not provide an inhaling of nuts with the nominal moment or have corrosion damages. Disks which have an excessive side or radial beating can cause vibration at the movement.

Disks for replacement have to be equivalent to original disks on a permissible load, diameter, a departure and the connecting sizes. Use of a disk of the improper size or type can affect a resource of a disk and the bearing, cooling of the brake mechanism, the indication of the speedometer / odometer, size of a road gleam.

Fig. 4.4. Scheme of measurement of a beating of disks

To measure a disk beating, it is necessary to use the exact indicator of hour type. The tire can remain on a disk or to be dismantled. The disk has to be installed on the balancing machine. Measure side 1 and a radial beating of 2 internal and external rims. Install the indicator of hour type and slowly turn a disk on one whole revolution, write down indications of the indicator (fig. 4.4).

When the measured beating exceeds norm, and correction by balancing is impossible, replace a disk. If the result of measurement was affected by traces of welding, paint or scratch, then the disk can be not changed.

Side beating: extreme a value – 1. 40 mm.

Radial beating: extreme b value – 1. 14 mm.

Fig. 4.5. Nut and hairpin of fastening of a wheel

On all models metric nuts and hairpins of fastening of a wheel (fig. 4.5) are used.

Carving of a nut and hairpin of fastening of a wheel of M12x1.25.

Description of uneven and/or premature wear

Uneven and premature wear has many reasons. Some of them: the wrong pressure in the tire, non-performance of shift of wheels, style of driving, the wrong angles of installation of wheels. In the presence of the following conditions it is necessary to rearrange wheels:

– wear of the forward tire differs wear of the back tire;

– neravnovnomerny wear on width of a protector of any tire;

– unequal wear of the left and right forward tires;

– unequal wear of the left and right back tires;

– wear spots, etc.

Fig. 4.6. Examples of uneven wear of tires: A – passing of turns at a high speed with a high pressure in tires or at non-compliance with shift of wheels; B – the wrong adjustment of angles of installation of wheels, heterogeneity of a design of the tire or the movement with sharp accelerations

Check of angles of installation of wheels is necessary in the presence of the following conditions:

– unequal wear of the left and right forward tires;

– neravnovnomerny wear on width of a protector of the forward tire;

– the protector of forward tires has sawtooth wear;

Fig. 4.7. Indicators of wear of tires

Original tires have the built-in indicators of wear of a protector 1 which show when tires need replacement (fig. 4.7).

These indicators 1 look as strips 12 mm wide when depth of a protector becomes equal 1,6 mm.

When indicators 1 appear in 3 or more flutes in 6 places, replacement of the tire is recommended.

The side beating is shown as cross movement here and there of a forward and/or back part of the car. It is caused by deformation of a framework of the tire. The side beating most is considerably shown at a small speed of 8-48 km/h.

Fig. 4.8. "Withdrawal" of the car at a side beating of the radial tire

It is possible to determine the defective tire by a trial trip. The back tire has defect if cross movement is made by a back part of the car. The driver on sitting feels as if someone pushed the car sideways (fig. 4.8).

If the forward tire is defective, then cross movement can be noticed visually.

The side beating can be quickly diagnosed by means of the device for failure detection of tires according to recommendations of the manufacturer of the device.

If there is no device for failure detection of tires on hand, it is possible to use a method of replacement by obviously serviceable tire / wheel though it takes more time.

Make a trip to define whether the side beating behind or in front takes place.

Establish tires and disks which are obviously serviceable (from the similar car), instead of those which serviceability raises doubts. If the zone of a side beating did not manage to be identified, replace back wheels.

Again make a trial trip. If there were changes, repeatedly establish one original wheels until the defective tire is found. If there are no changes, establish a set of obviously serviceable wheels. After that again establish one original wheels and carry out similar check.

Withdrawal represents a car deviation from a rectilinear trajectory of the movement on the road with a small bias without effort on a steering wheel. Withdrawal usually is caused by the following conditions.

Inappropriate tire and wrong adjustment of angles of installation of wheels.

Unevenness of brake efforts.

Tire design.

Fig. 4.9. Recommendations of the manufacturer of the equipment

Constructive defect of the tire can cause withdrawal of the car. An example of it is placement of a brekerny belt. The brekerny belt of radial tires located not on the center can force the tire to develop side force at its rotation at movement along the road. If one party of the tire has diameter a little more, than other party, then tire will tend to unilateral withdrawal. At the same time there is side force which can cause withdrawal of the car. In order that it is wrong not to take the wrong adjustment of angles of installation of wheels for withdrawal of the tire, it is necessary to follow the procedure in the figure 4.9.

If the tire with an average or big run is rearranged on other party of the car, be convinced that smoothness of the course did not worsen

Back tires will not cause withdrawal.