Caster; Thrust Angle; Wheelbase Difference - Launch X-631 Plus User Manual

LAUNCH
Correct Kingpin Inclination can equalize the loads
applied on bearings so that the life of bearings can be
prolonged and the controllability of steering is
improved.
Without the inclination, the controllability of the
steering may be affected; further more, the vehicle
weight and the ground counterforce may cause
significant stress in the axle and finally damage the
axle.
Correct inclination of king pin is also helpful for the
vehicle to restore its straight-ahead position after
steering.
Kingpin Inclination is determined when the vehicle
suspension is designed. It is not service adjustable.

Caster

Caster is the tilting of the kingpin either forwards or
backwards from vertical, as viewed from side of the
vehicle. See Fig.1.4
When the king pin is tilted backwards from the vertical,
caster is positive. When the king pin is tilted forwards,
caster is negative.
Caster angle influences the directional stability of the
X-631/ X-631+ Wheel Aligner
Fig.1.3
Fig.1.4
steering. To increase the tendency of the steering to
self-centre, the steering will normally be designed
with positive caster.

Thrust angle

The thrust angle is defined according to the driven
mode of vehicle.
z Rear wheel driven: the thrust angle equals half of
the toe-in difference between the two rear wheels.
As shown in Fig.1.5.
z Front wheel driven: the thrust angle equals half
of the toe-in difference between the two front
wheels.
z Four-wheel driven: the thrust angle equals half of
the toe-in difference between the two front
wheels plus half of the toe-in difference between
the two rear wheels.
The thrust angle is defined as positive when the
thrust line is towards left and negative when the line
is towards right.
If the thrust angle is not zero, the vehicle will have the
side-moving trend. In this case, adjust the front toe-in
of the drive wheels first, and then adjust the toe-in of
driven wheels.

Wheelbase Difference

Wheelbase difference is defined as the angle
between the joint line of the centre of two rear wheels
and that of the front wheels. It is positive when
distance between the centre of the right wheels is
large than that of left wheels; and negative otherwise.
If the tread is available from the vehicle specifications,
then the wheelbase difference can be also expressed
by angle. See Fig. 1.6
1-2
Introduction
Fig.1.5