4.1.11. Unilateral wear
Style of driving, but sometimes and the wrong adjustment of angles of installation of wheels is the reason of unilateral wear in many cases.
The increased side wear
Side wear, most often in combination with attritions on edges of a protector and thin cuts, arises always when tires work at extremely big angle of side withdrawal and therefore "tinder" on a paving (fig. 4.6)
Bystry driving on the sites abounding with turns results in particular on external shoulders of the tire in the increased wear.
The rounded-off external shoulder of the tire together with high degree of wear of external blocks of a protector speaks about bystry driving in bends. Such wear turns out because of the corresponding style of driving.
For optimization of riding qualities the running gear is adjusted on certain parameters of a convergence and disorder of wheels. If tires are operated at excellent from the set conditions, it is necessary to reckon with the unilateral and increased wear.
Especially the RUUK wrong parameters can result in bigger unilateral wear, besides danger of uneven wear increases.
The distance between wheels in front A is more, than B distance behind (the C direction of the movement).
Convergence or positive convergence
|Fig. 4.8. Convergence or positive convergence
The distance between wheels in front of A is less, than B distance behind (the C direction of the movement).
To avoid unilateral wear of tires, it is necessary you watch that the angles of installation of wheels always were in limits of the admission of car maker. Most often the angles of installation of wheels deviate nominal parameters because of external influence, for example rigid contact with a border at the parking.
At RUUK it is possible to define whether there are angles of installation of wheels within the admission or it is necessary to adjust them.
Changes in a running gear
Use of "a set of the shortened springs" and/or the light-alloy wheels which are not allowed by Audi can lead to the angles of installation of wheels which differ from put by a design.
Even if the angles of installation of wheels during RUUK at the motionless car are normal, because of the changed height and the provision of wheels during the movement the nature of the movement of a suspension bracket of wheels can change.
Thus, uneven wear is previously programmed.
Wear of the central part of a protector
This nature of wear is shown on driving wheels of cars with powerful engines which often pass long distances at great speed.
At high speeds diameter of the tire due to centrifugal force increases in the middle of a protector more, than at the edges. Thereof driving force is transferred to a roadbed from a middle part of a protector. This fact affects in turn the nature of wear.
Especially considerably such wear is shown on wide tires.
Pressure decrease of air in tires will not possible to avoid such wear.
For the safety reasons it is not necessary to reduce air pressure in tires below ordered at all.
More or less uniform wear can be reached due to timely shift of wheels from the leader on not driving axis.
The increased wear of a protector
|Fig. 4.9. The increased wear of a protector
Typical picture of wear of the tires installed on driving wheels of the car with the powerful engine (fig. 4.9)
Bigger wear of a middle part of a protector of tires is a consequence of the loadings arising because of centrifugal force of the tire and transfer of driving force on a roadbed.