Chevrolet 1977 light duty truck, Service Manual

Page: 191 / 861

SECTION 3A
FRONT ALIGNMENT
C O N T E N T S
3 A- 1
3A-2
3A-6
GENERAL DESCRIPTION
G eneral D e s c r ip tio n ...................
M ain te n a n c e and Adjustm ents
Specifications.................................
F R O N T A L IG N M E N T
The term " f r o n t alig n m e n t" refers to the angular
relationships between the front wheels, the front
suspension attaching parts and the ground.
The pointing in or "to e -in " o f the front wheels, the
tilt o f the front wheels from vertical (when viewed from
the front o f the vehicle) and the tilt o f the suspension
m e m b e rs from vertical (when viewed from the side of
the vehicle), all these are involved in fro n t alignment.
The various factors that enter into front alignment are
covered here each one und er its own heading.
CASTER
Caster is the tilting o f the fro n t steering axis either
forw ard or backward from the vertical (when viewed
from the side o f the vehicle). A backward tilt is said to
be positive ( + ) and a forward tilt is said to be negative
( - ) .
O n the short and long arm type suspension you
can n o t see a caster angle without a special instrument,
but you can un d erstan d that if you look straight down
from the top o f the upper control arm to the ground you
would lind th at the ball joints do not line up (fore and
aft) w hen a caster angle o th e r th an 0° is present. If you
had a positive caster angle the lower ball joint would be
slightly ahead (toward the front o f the vehicle) o f the
u pper ball jo in t center line. In short then, caster is the
forw ard or backward tilt o f the steering axis as viewed
from a side elevation. Caster is designed into the front
axle assembly on all K series vehicles (l'our-wheel drive),
an d is n o n -a d ju sta b le . See caster copy u n d e r
A D JU S T M E N T S .
CAM BER
C am b er is the tilting o f the front wheels from the
vertical when viewed from the front o f the vehicle.
W hen the wheels tilt outward at the top, the c a m b e r is
said to be positive ( + ) . W h e n the wheels tilt inward at
the top, the cam b er is said to be negative (—). The
am o u n t o f tilt is m easured in degrees from the vertical
and this m easurem ent is called the c a m b e r angle.
C a m b e r is designed into the front axle assembly o f all K
series vehicles and is non-adjustable. See ca m b e r copy
under A D JU S T M E N T S .
TOE-IN
Toe-in is the turning in o f the front wheels. The
actual am ount o f toe-in is normally only a fraction o f an
inch. The purpose o f a toe specification is to ensure
parallel rolling o f the front wheels. (Excessive toe-in or
toe-out will cause tire wear). Toe-in also serves to offset
the small deflections o f the wheel support system which
occurs when the vehicle is rolling forward. In other
words, even w hen 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 JU S T M E N T S .