10.2. Angles of installation of forward wheels
The convergence is a difference of distances between onboard zakraina of the rims measured behind and ahead of wheels at the level of their centers. The positive convergence means that wheels are ahead located more closely to each other, than behind, at the level of their centers. The convergence exerts impact on straightforwardness of the movement of the car and its controllability. Thanks to a convergence forward wheels rotate in parallel. At turn of the car because of an arrangement of steering drafts in the form of a trapeze the convergence passes into "divergence". The wheel located on the internal radius of turn turns on a bigger corner, than the wheel which is on the external radius of turn. It is caused by the fact that at turn internal wheels have to circle smaller radius, than external. It automatically supports efforts on turn and a trajectory of the movement of the car. At adjustment of angles of installation of wheels the convergence always has to be corrected in the last turn.
Wheel tilt angle
Fig. 10.3. Wheel tilt angle: and – a positive tilt angle of a wheel; b – negative tilt angle of a wheel; with – the vertical plane
The inclination is a deviation forward or back the most top part of an axis of turn from the vertical which is carried out through a point of fastening of a wheel in the longitudinal plane of the car (fig. 10.3). The inclination is called positive back (+), an inclination forward – negative. The inclination of an axis of turn influences stability of the car on the road, but does not influence intensity of wear of tires. Weak springs and an overload of the car can influence the size of an inclination.
If one wheel has a bigger positive inclination, than other wheel, it will lead to what this wheel will pull to the center of the car. As a result the car will take away towards a wheel with a smaller positive inclination.
The corner of a cross inclination of an axis of turn is measured in degrees and is not subject to adjustment.
Disorder of wheels
Fig. 10.4. Corner of disorder of wheels: and – a disorder corner; b – negative corner of disorder; with – a positive corner of disorder; d – vertical plane
Disorder is a corner between the plane of rotation and a vertical of a wheel (fig. 10.4). It can be positive if wheels are inclined outside, or negative if wheels are inclined inside. The disorder corner generally influences uniformity of wear of tires of forward wheels. If the corner of disorder of one wheel positive, and another – negative, then takes away the car aside at the movement on a straight line.
If at the car the excess size of positive disorder, wears out an external shoulder of the tire. In the same way, at excessively negative size of disorder the internal shoulder of the tire will wear out.
The inclination as well as disorder, is measured in degrees and is not regulated.
Turn axis tilt angle
Fig. 10.5. Axis tilt angle turn/angle of entry: and – a disorder corner; b – lower spherical hinge; with – a corner of a longitudinal inclination of an axis of turn; d – angle of entry; е – vertical plane
The tilt angle of an axis of turn is a deviation (in the top part) a rotary fist from a vertical (fig. 10.5). The tilt angle of an axis of turn is measured between the vertical plane and the line passing through the center of a rack and the lower spherical hinge if to take a detached view of the car.
The inclination of an axis of turn supports the rectilinear movement and promotes return of wheels to the provision of rectilinear advance. Cars with forward driving wheels have to have a negative turn axis tilt angle size.
Angle of entry
The angle of entry is the corner measured from a corner of disorder of wheels to the line passing through the center of a rack and the lower spherical hinge if to take a detached view of the car.
The angle of entry pays off in degrees, however is not measured directly. For definition of an angle of entry it is necessary to add positive to the size of a tilt angle of an axis of turn or to subtract from it negative value of a corner of disorder.
Running in shoulder
Fig. 10.6. Running in shoulder: and – the central line passing through the top support of a rack and the hinge; b – central fading, passing through a wheel and the tire; with – crossing of lines over the surface of the road; d – running in shoulder
The shoulder of a running in is a distance between the line running to a surface roads through the center of a rack and the lower spherical hinge, and actual "0" or a true vertical (fig. 10.6). The shoulder of a running in is stuffed up in a design of the car and cannot be measured or adjusted.
Shift is back a distance on which the axis of one forward wheel can be displaced in comparison with an axis of other forward wheel back. Shift is caused, mainly, by roughnesses of the road or collision with other car back.
Angle of rotation
The angle of rotation is a corner on which each forward wheel when the car does turn can turn.
Driving under the influence of torque transmission
Influence on management of size of torque transmission is a line, the general for all cars with the forward drive. The car will pull or take away in one direction at strong acceleration, and at reduction of speed – to pull and take away in other direction. It is normal though some buyers can consider this phenomenon unusual. It can be explained in the best way, having pointed that transmission of cars with the forward drive has various length of power shafts. Because of it both power shafts tend to twisting, but longer axis will be twisted slightly stronger, than short. It forces one wheel to rotate quicker, than and it is slightly stronger to pull another forward.
It is necessary to remember that this phenomenon does not influence negatively neither car service life, nor safety of the driver.
Management under the influence of memory
Management under the influence of memory is such situation at which after turn in one direction the car "will want" to continue the movement in this direction. Having done turn in other direction, the car "will want" to move further in this other direction. This very strange situation usually arises when the depreciation nut on McPherson rack is too hardly tightened.
By searches of the possible reason of this phenomenon check deformation of the rack steering mechanism, and also failure of the spool-type valve on cars with the amplifier of steering.