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FRONT END ALIGNMENT
3A-1
SECTION 3A
FRONT END ALIGNMENT
CONTENTS OF THIS SECTION
General Description
...............................................................................................
3A-1
Maintenance and Adjustments
.................................................................................
3A-1
Preliminary Checks
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3A-1
Alignment Requirements
......................................................................................
3A-2
Adjustments (Except H Series)
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3A-3
Correction Charts
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3A-4
Adjustments (H Series)
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3A-4
Trim Heights
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3A-10
Specifications
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3A-12
GENERAL DESCRIPTION
FRONT ALIGNMENT
Front alignment refers to the angular relationship
between the front wheels, the front suspension attaching parts
and the ground. The angle of the knuckle away from the
vertical, the pointing in or "toe-in" of the front wheels, the
tilt of the front wheels from vertical (when viewed from the
front of the vehicle) and the tilt of the suspension members
from the vertical (when viewed from the side of the vehicle),
-
all these are involved in front alignment.
CASTER (FIG. 3A-1)
Caster is the tilting of the front steering axis either
forward or backward from the vertical (when viewed from
the side of the vehicle). A backward tilt is said to be positive
(+)
and a forward tilt is said to be negative
(-).
On the short
and long arm type suspension a caster angle can not be seen
without a special instrument, but you can understand that if
you look straight down from the top of the upper control arm
to the ground you would find that the ball joints do not line
up (fore and aft) when a caster angle other than
O"
is present.
If you had a positive caster angle the lower ball joint would
be slightly ahead (toward the front of the vehicle) of the upper
ball joint center line. In short then: caster is the forward or
backward tilt of the steering axis as viewed from a side
elevation. See caster copy under ADJUSTMENTS.
CAMBER (FIG. 3A-1)
Camber is the tilting of the front wheels from the vertical
when viewed from the front of the vehicle. When the wheels
tilt outward at the top, the camber is said to be positive
(+).
When the wheels tilt inward at the top, the camber is said
to be negative
(-).
The amount of tilt is measured in degrees
from the vertical and this measurement is called the camber
angle. See camber copy under ADJUSTMENTS.
TOE-IN (FIG. 3A-1)
Toe-in is the turning in of the front wheels. The actual
amount of toe-in is normally only a fraction of an inch. The
purpose of a toe specification is to insure parallel rolling of
the front wheels (excessive toe-in or toe-out may increase tire
wear). Toe-in also serves to offset the small deflections of the
wheel support system which occurs when the vehicle is rolling
forward. In other words, even when the wheels are set to
toe-in slightly when the vehicle is standing still, they tend to
roll parallel on the road when the vehicle is moving. See toe-in
copy under ADJUSTMENTS.
MAINTENANCE AND
ADJUSTMENTS
PRELIMINARY CHECKS PRIOR TO
ADJUSTING FRONT ALIGNMENT
Steering and vibration complaints are not always the
result of improper alignment.
An additional item to be checked is the possibility of tire
lead due to worn or improperly manufactured tires. "Lead"
is the deviation of the vehicle from a straight path on a level
road without hand pressure on the steering wheel.
Section 3E of this manual, "Wheels and Tires", contains
a procedure for determining the presence of a tire lead
problem.
Before making any adjustment affecting caster, camber
or toe-in, the following checks and inspections should be
made to insure correctness of alignment readings and
alignment adjustments:
I. Check all tires for proper inflation pressures and
approximately the same tread wear.
2. Check front wheel bearings for proper adjustment and
correct if necessary.
3. Check for loose ball joints by following the inspection
procedure presented later; check tie rod ends and steering
relay rods; if excessive looseness is noted, it must be corrected
before adjusting.
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