SECTION 10: FRONT AXLE
DOB 2490-2789 | X3-45 Commuter PA1605 Maintenance Manual (Final Version – Rev.2 April 2016)
9
FIGURE 3: CAMBER
10006
6.6.1 Camber
Check
For camber specifications, refer to paragraph
8: ‘’Specifications’’ in this section
1. Use an alignment machine to check the
camber angle.
2. If camber reading is not in the
specifications, check the wheel bearings
and repeat the check. If the reading is still
not within specifications, verify the steering
knuckle pins and axle center.
3. Check the wheel lateral distortion as
instructed in Section 13,
‘’Wheels, Hubs
and Tires’’
under heading,
‘’Checking for
Distorted Wheel on Vehicle’’
. If distortion is
excessive, straighten or replace wheel(s).
6.7
FRONT AXLE CASTER
For caster specifications, refer to paragraph
8: ‘’Specifications’’ in this section.
Positive caster is the rearward tilt from the vertical
axis of the knuckle pin. Negative caster is the
forward tilt from the vertical axis of the knuckle pin
(Figure 4). This vehicle is designed with a
positive caster. The purpose of the caster angle is
to give a trailing effect. This results in stabilized
steering and a tendency for the wheels to return
to the straight-ahead position after taking a turn.
FIGURE 4: CASTER
10007
Excessive caster results in hard steering around
corners. A shimmy may also develop when
returning to the straight ahead position (pulling
out of curves).
Insufficient caster will cause wandering and
steering instability. Caster variations may be
caused by a bent axle, tilting or distortion of the
side suspension supports, damaged radius rod
bushings, or unequal tightening of the front and
rear suspension support bolts. Incorrect caster
must be corrected by replacing the damaged
suspension parts. A precision instrument should
be used to measure the caster.
NOTE
The caster of this vehicle is factory set and is
not adjustable. However, if after replacing
damaged parts or in case of improper caster
due to irregular setting, the front axle caster
needs adjustment; it can be adjusted by means
of shims (Prevost #110663) on the left-hand
side upper radius rod support in order to obtain
minor adjustment.
6.8
FRONT WHEEL TOE-IN
Wheel toe-in is the degree (usually expressed in
fractions of an inch) to which the forward part of
the vehicle front wheels are closer together than
the rear part, measured at wheel centerline height
with the wheels in the normal ‘’straight-ahead’’
position of the steering gear.
Incorrect toe-in results in excessive tire wear
caused by side slippage and also steering
instability with a tendency to wander. Toe-in may
be measured from the center of tire tread or from
the inside of the tires. Take measurements at
both front and rear of axle (see ’’A and ‘’B’’ in
Figure 5).
