Alignment Angles - Ranger 3DP4100 Operation Manual

ALIGNMENT ANGLES

When vehicle wheel alignment is considered, there are
three main angles that should not be ignored. These are:
CASTER, CAMBER, and TOE. While these are prevalent,
you should not overlook the other angles, because they will
provide you a method of troubleshooting when dealing with
a vehicle's suspension.
In cases of a major change to a vehicle's suspension, for
example due to repair, the alignment is typically performed
doing Caster first, then Camber, followed by Toe. If major
changes are made, all angles should be re-checked and
verified after adjustments have been made.
CAMBER ANGLE
Camber is the angular measurement of the outward or
inward tilt of the center-line of the wheel from true vertical
at the top of the wheel. Positive camber is defined as an
outward tilt from vertical, and negative camber would be an
inward tilt. Camber is a tire wearing angle, and is usually
adjustable. In cases where a factory adjustment is not available
often there are shims or kits to make adjustments possible.
MEASUREMENT METHOD
This angle is read from an electrolytic vial (or on some older
units, an electronic inclinometer) on each wheel unit.
WHAT CAMBER DOES
Camber helps to position the weight of the vehicle
over the point where the tire contacts the road, thus
placing the vehicle load on the inner wheel bearing.
NEGATIVE CAMBER
Negative Camber is used to ensure an even tire contact
during cornering. Excessive negative camber can cause inside
tire wear. The vehicle will pull to the side with the most positive
camber if there is a difference in camber angle between sides.
POSITIVE CAMBER
Positive Camber is often used to induce understeer in
some cars during hard cornering where most drivers cannot
drive oversteer conditions that may be caused by negative
camber. Excessive positive camber will cause outside tire wear.
The vehicle will pull to the side with the most positive camber.
ADJUSTMENT METHODS
Shims, Cams, Slotted Frame, Strut Rotation, Wedges, Ball
Joint Rotation, Offset Bearing Plates, Cam Bolts, Offset
Bushings, Offset Ball Joints.
S.A.I. ( STEERING ANGLE INCLINATION )
ALSO KNOWN AS:
K.P.I. ( KING PIN INCLINATION )
B.J.I. ( BALL JOINT INCLINATION )
Steering Angle Inclination (S.A.I.) is the angular measure-
ment of the inward tilt at the top from true vertical of the
axis created by the front strut, ball joints, or kingpin of
the vehicle's suspension. It is a non-adjustable angle. It
may, however, change when any adjustment for camber is
made. This will vary with different front suspension designs
(MacPherson strut, short/long arm, I Beam, solid axle, etc).
MEASUREMENT METHOD
S.A.I. is calculated from readings taken from the Camber/
Pitch level vial during the caster swing. S.A.I. does not con-
tribute directly to tire wear.
WHAT SAI DOES
S.A.I. aids in weight distribution particularly on turns. It
provides directional control stability and steering wheel
return along with Caster. S.A.I. is always a positive angle,
since by design a negative angle in not possible. S.A.I. may
also be called B.J.I. (Ball Joint Inclination) or K.P.I. (King
Pin Inclination).
INCLUDED ANGLE
10