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HEAVY DUTY ALIGNMENT ANGLES
Camber
Definition: The inward (-) or outward (+) tilt
of the top of the tire.
Purpose: Camber helps to properly load the wheel bearings, and
to maintain a straight ahead path. If the tire leans too far
inward (-) or outward (+), not only may it accelerate wheel bearing
wear, but can also wear the tire on the side to which it is leaning.
Adjustment: Most I-Beams are corrected by replacing the axle.
Some shops bend or “correct” the axle angle*. Independent
suspensions are usually shimmed. |
Caster
Definition: The forward (-) or backward (+) tilt
of the kingpin or steering axis.
Purpose: Proper Caster helps the steering to return to center
and assists the vehicle in maintaining a straight ahead path
while providing stability.
Adjustment: Most I-Beams are tilted with a wedge, usually
using the same wedge angle on each side, thus increasing
(+) or decreasing (-) the total Caster for the axle. Sometimes
different wedge angles are used side to side*. Some shops
twist or “correct” the axle angle*. Some suspensions
use parallel adjustable torque arms. |
Toe
Definition: The difference between the leading edges of the
front of the tires and the trailing edges of the rear of the tires on the
same axle. Tires too close together at the front (+) or too far apart at
the front (-) may lead to tire wear.
Purpose: Proper Toe setting aids in directional stability and proper tire
wear. If the toe is too negative, the vehicle may have a wander or pull
condition.
Adjustment: Total toe is adjusted with one or two turn-buckle style tie
rods. |
Thrust
Angle
(One or multiple rear axles)
Generally the rear axles need to be perpendicular
to the centerline of the frame, and parallel to each other.
Definition: Simply put, Thrust Angle is the average direction
an axle points away from the centerline of the frame, (+
is to the right and – is to the left).
Purpose: Thrust angle will always determine the vehicle
direction of travel. Therefore in line with the Vehicle
Centerline is generally preferred, but never pointed to
the right side.
Adjustment: Normally Thrust is adjusted with either a shim
or a torque rod with a threaded sleeve. Occasionally an
eccentric sleeve is installed at an end bushing. |
Axle
Offset Angle
Definition: The position of an axle relative to the frame rails, side
to side. It should be positioned equally under the frame.
Purpose: When an axle becomes offset to the frame, it can accelerate suspension
and drive line wear, affect the axle torque and may lead to a handling condition.
Adjustment: When adjustable, rear axles typically are adjusted with shims. |
*CAUTION: Always consult vehicle manufacturer and manufacturer
of correction equipment for procedure and appropriateness for
the vehicle that is being worked on.
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