40.1 - 0010 General
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Notes on alignment check The "Beissbarth P5 wheel-alignment analyzer" was used for the alignment check shown in the figure. Obviously other measuring equipment or facilities approved by us may be used, see "Folder test report or workshop equipment". |
Please observe operating instructions of the individual manufacturers. A 3-axle vehicle was used as a base. All other vehicle models may be checked in accordance with this description. |
1 Graduated straightedge P 1-2
2 Brake tensioner P 8-06 or
special tool 000 589183100
3 Turning pad P 1-15
4 Projector bracket P 1-69
5 Projector P 8-20 / P 8-21
6 Transformer (12 V DC) P 8-52
7 Wheelbase gauge
8 Dial gauge with base P 22
9 Compensating bridge P 1-40
10 Measuring instrument P 1-35
11 Scale trestle P 1-99
12 Locking bars P 8-69
In order to reduce the steering effort and to improve the directional stability the front wheels must assume a certain wheel position relative to the road surface and to the driving direction. The steering-geometrical terms all have a certain interrelationship and determine the operating characteristics of the vehicle. | Toe, wheel lock, axle offset errors and wrong tire pressure are the most frequent causes of tire wear and difficult steerability of the vehicle. All axles must be exactly at right angles to the longitudinal symmetry axis of the vehicle. The axles may neither be offset laterally. |
Toe-in
The toe-in is the dimension of the front distance of the wheels compared with the rear distance in mm. The measurement is taken on the rim flange in the center of the wheel with "straight-ahead position" of the wheels.
With positive toe (= toe-in) the wheels point to the inside, i.e. a < b.
The toe-in stabilizes straight-ahead operation by creating forces on the tire contact surfaces. These forces prevent a divergence and fluttering of the wheels in operation. The toe-in eliminates the clearance in the wheel suspension and the tie rod ends. However, it also has a significant influence on the cornering behaviour of the vehicle.
The wheel toe is adjusted by turning the tie rod ends or tie rod tubes.
Camber
The camber is the angle of inclination of the wheels relative to the vertical axis. It is measured in degrees with "straight-ahead position" of the wheels. With a positive camber the wheels are facing outward at the top.
The camber values must be the same on both wheels in order to avoid lateral pulling and to ensure straight-ahead operation.
The camber on rigid axles is a design parameter and not adjustable.
Caster
This is the angle of inclination of the kingpin (A) in longitudinal direction of the vehicle so that the extended center line (C) of the kingpin is positioned in front of the wheel contact point (B).
The caster ensures that the wheels are pulled and not pushed. This ensures wheel stability.
In combination with the forces resulting from the kingpin inclination the caster creates a steering resetting force which spontaneously returns the deflected wheel to the straight-ahead position.
The caster is adjusted by placing wedges between leaf spring and axle.
Kingpin inclination
The kingpin inclination is the angle by which the kingpin at the top is inclined towards the trans-verse vehicle axis inside relative to the vertical axis. This parameter is measured in degrees at a steering lock of 20°.
The kingpin inclination creates resetting forces which, after driving through a curve, returns wheels and steering wheel to straight-ahead position. Camber and kingpin inclination determine the size of the steering offset.
The kingpin inclination is a design parameter and not adjustable.
Steering offset
Distance between wheel contact point (A) and the point where the extended center line of the kingpin (B) meets the road surface.
One distinguishes:
Positive steering offset
The meeting point of the extended center line of the kingpin is inside the wheel contact point.
Negative steering offset
The meeting point of the extended center line of the kingpin is outside the wheel contact point.
Zero steering offset
The meeting point of the extended center line of the kingpin and the wheel contact point are identical.
The steering forces are influenced by the steering offset.
The steering offset constitutes a lever on which the road surface influences and braking forces act.
Track differential angle
The track differential angle is the angular difference between the curve inner wheel and the curve outer wheel when driving through curves. It is measured in degrees with 20° steering lock of the curve inner wheel. The difference of the two lock angles is the track differential angle.
On vehicles with two steered front axles the lock angles of all steered front wheels are measured with the curve inner wheel of the first front axle positioned at 20° lock.
Wheels roll in curves along circular arcs without skidding only if the curve inner wheel lock is greater than that of the outer wheel. Regardless of steering lock the extended wheel axes must
intersect in the center point of the curve.
The comparison of the track differential angles with left and right-hand lock provides information on the steering trapeze and the even setting of the front wheel toe. Its comparison also allows the detection of faults on steering parts (e.g. bent steering knuckle arms or steering arms or wrongly positioned pitman arms).
Wheelbase
Wheelbase is the distance between the axles measured from wheel center to wheel center.
Lateral offset of rear axle
Displacement (dimension s) of the axle center relative to the frame center.
Note
This applies in principle also to all other axles.
Rear axle inclination
The rear axle is not positioned parallel to the front axle. Inclination (angle a) of the rear axle results in instable straight-ahead operation.
Note
Also applicable in principle to all other axles.
An inclination of the front axle can only be established by mechanical measurement, e.g. via wheelbase.