Chevrolet Light Duty Truck 1973, Руководство по обслуживанию

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3 -1 0 FRONT S U S PEN SIO N
CAMBER
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.
Camber is designed into the front axle assembly of all K
series vehicles and is non-adjustable. See camber copy
under ADJUSTMENTS.
TOE-IN
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 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
ADJUSTMENTS.
TOE-OUT ON TURNS (Fig. 16)
Toe-out on turns refers to the difference in angles
between the front wheels and the vehicle frame during
turns. Since the inner wheel turns a smaller radius than
the outer wheel, when rounding a curve, it must be at a
sharper angle with respect to the vehicle frame. That is,
the inner wheel must toe-out more than the outside
wheel toes-in. This condition is desirable because it
allows the front wheels to turn in a concentric circle.
Note in fig. 16 that the right front wheel centerline (B)
and the left front wheel centerline (C) intersect the
centerline of the rear axle (A) at the same point (D). The
20° and 23° angles are not necessarily representative of
any vehicle and are used here for theory only.
If “Toe-Out on Turns” is found to be other than
specified for a specific vehicle it might indicate that some
front suspension part is bent and a visual inspection is
necessary.
The angle of the steering arms is the determining factor
of toe-out on turns. If either arm is bent, toe-out on turns
will be affected.
This steering arm angle is not adjustable, so a bent arm
must be replaced. Since it is unlikely that both arms will
be bent, follow the procedure below to determine which,
if either, arm is bent.
Measurement
Measure the distance between the suspected bent arm
and a stationary point on the brake backing plate or
splash shield, comparing it with the same measurement
on the other arm. The angle of the steering arms must be
the same for both arms. Toe-out on turns is not
adjustable.
STEERING AXIS INCLINATION (S.A.I.) FIG. 17
Steering axis inclination (formally called kingpin
inclination on conventional suspensions) is the inward
slant (at the top) of the steering knuckle from the
vertical. This inclination tends to reduce road shock on
the steering system by allowing the steering systems
centerline to intersect the tire centerline near the point
where the tire contacts the road. The inward slant or
inclination of the steering knuckle tends to keep the
wheels straight ahead. The reason for this is as follows:
When the front wheels are straight ahead the steering
knuckle spindles are practically horizontal. As the wheels
are turned away from the straight ahead the outer ends
of the spindle tries to lower or get closer to the ground.
However, because the spindles are fixed in the hub
assembly they cannot get closer, or lower, to the ground.
So the spindles force the steering knuckles to raise the
front of the vehicle.
After a turn is complete, and force applied to the
steering wheel is released, the weight of the vehicle on
the spindles tends to help the front wheels return to a
straight ahead position. “Steering Axis Inclination” is a
designed in angle and is non-adjustable.
PRELIMINARY ADJUSTMENTS FIG. 19-21
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.
1. Check all tires for proper inflation pressures and
approximately the same tread wear.
2. Check front wheel bearings for looseness (.001-.008
end play is correct) and adjust if necessary.
3. Check for looseness of ball joints, tie rod ends and
steering relay rods, if excessive looseness is noted, it
must be corrected before adjusting.
4. Check for run-out of wheels and tires.
5. Check vehicle trim heights; if out of specifications
and a correction is to be made, the correction must
be made before adjusting caster, camber or toe-in.
NOTE: Good judgment should be exercised
before replacing a spring when vehicle trim
height is somewhat out of limits (± 3/4").
6. Consideration must be given to excess loads, such as
tool boxes. If this excess load is normally carried in
the vehicle it should remain in the vehicle during
alignment checks.
7. Consider the condition of the equipment being used
to check alignment and follow the manufacturer’s
instructions.
8. Regardless of equipment used to check alignment
the vehicle must be on a level surface both fore and
aft and transversely.
LIGHT DUTY TRUCK SERVICE MANUAL