Spicer Dana Spicer Steer Axles - Service Manaul - Manual (Page 20)

16
Alignment / Adjustment
Caster Adjustment
Caster is the fore and aft tilt (toward front or rear of vehicle) of
the steering kingpin as viewed from the side of the vehicle .
“Positive” caster is the tilt of the top of the kingpin toward the
rear of the vehicle .
“Negative” caster is the tilt of the top of the kingpin toward the
front of the vehicle.
Also Reference RP 642, Guidelines for Total Vehicle Alignment
published by the Truck Maintenance Council.
A caster angle more positive than specified may result in
excessive steering effort and/or shimmy. An angle less positive
may result in vehicle wander or poor steering return to
center. Caster angle is determined by the installed position of
the steer axle.
Caster is adjusted by adding or removing taper wedges
between the springs and axle beam mounting pad.
The caster angle is generally more positive with power steering,
since the power-assist overcomes excessive steering
effort. This enables the vehicle to exhibit maximum straight
ahead steering stability (common range for power steering
units is +2° to +4°).
Refer to OEM vehicle specifications.
Note: Adjust caster to vehicle manufacturer specifications.
Spicer expressly prohibits twisting of axle beam for
caster adjustment or any straightening purposes.
Note: Changing the torquing sequence on U-bolts may result
in slight changes in caster.
1 - Vertical center line
2 - Kingpin center line
3 - Front of truck
4 - Rear of Truck
1 - Kingpin center line
2 - Vertical center line
3 - Front of truck
4 - Rear of truck
4 3
1
2
4 3
2
1
CAUTION