GMC 1982 Light Duty Truck, Service Manual

Page: 229 / 1435

FRONT ALIGNMENT 3A-1
SECTION 3A
FRONT ALIGNMENT
CONTENTS
3A-I
3A-2
3A-5
General D escrip tio n ..................
Maintenance and Adjustments
Specifications...............................
GENERAL DESCRIPTION
FRONT ALIGNMENT
The te rm " fro n t a lig n m e n t" refers to the a n g u la r
relationships between the front wheels, the front suspension
attaching parts and the ground.
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 vertical (when viewed from the side of the vehicle), all
these are involved in front alignment. The various factors
that enter into front alignment are covered here each one
under its own heading.
CASTER
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 you cannot
see a caster angle 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 0° 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. Caster is designed into the
front axle assembly on all K series vehicles (four-wheel
drive), and is non-adjustable. See caster copy under
A D J U S T M E N T S .
CAMBER
Cam ber 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
cam ber is said to be negative (-). The amount of tilt is
measured in degrees from the vertical and this measurement
is called the cam ber angle. C am ber is designed into the front
axle assembly of all K series vehicles and is non-adjustable.
See cam ber copy under A D J U S T M E N T S .
TOE-IN
Toe-in is the turning in of the front wheels. The actual
am ount of toe-in is normally only a fraction of an inch. The
purpose of a toe specification is to ensure parallel rolling of
the front wheels. (Excessive toe-in or toe-out will cause 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 A D J U S T M E N T S .