850 Wheel alignment theory operation

850 Wheel alignment theory operation
1995 Volvo 850
Wheel Alignment Theory & Operation
This article is intended for general information purposes
only. This information may not apply to all makes and models.
Before adjusting wheel alignment, check the following:
Fig. 1:
Each axle uses tires of same construction and tread style,
equal in tread wear and overall diameter. Verify that radial
and axial runout is not excessive. Inflation should be at
manufacturer’s specifications.
Steering linkage and suspension must not have excessive play.
Check for wear in tie rod ends and ball joints. Springs must
not be sagging. Control arm and strut rod bushings must not
have excessive play. See Fig. 1.
Checking Steering Linkage
Vehicle must be on level floor with full fuel tank, no
passenger load, spare tire in place and no load in trunk.
Bounce front and rear end of vehicle several times. Confirm
vehicle is at normal riding height.
Steering wheel must be centered with wheels in straight ahead
position. If required, shorten one tie rod adjusting sleeve
and lengthen opposite sleeve (equal amount of turns). See
Fig. 2.
Wheel bearings should have the correct preload and lug nuts
must be tightened to manufacturer’s specifications. Adjust
camber, caster and toe-in using this sequence. Follow
instructions of the alignment equipment manufacturer.
CAUTION: Do not attempt to correct alignment by straightening parts.
Damaged parts must be replaced.
Fig. 2:
Adjusting Tie Rod Sleeves (Top View)
1) Camber is the tilting of the wheel, outward at either top
or bottom, as viewed from front of vehicle. See Fig. 3.
2) When wheels tilts outward at the top (from centerline of
vehicle), camber is positive. When wheels tilt inward at top, camber
is negative. Amount of tilt is measured in degrees from vertical.
Fig. 3:
Determining Camber Angle
1) Caster is tilting of front steering axis either forward or
backward from vertical, as viewed from side of vehicle. See Fig. 4.
2) When axis is tilted backward from vertical, caster is
positive. This creates a trailing action on front wheels. When axis is
tilted forward, caster is negative, causing a leading action on front
Fig. 4:
Determining Caster Angle
Toe-in is the width measured at the rear of the tires
subtracted by the width measured at the front of the tires at about
spindle height. A positive figure would indicate toe-in and a negative
figure would indicate toe-out. If the distance between the front and
rear of the tires is the same, toe measurement would be zero. To
1) Measure toe-in with front wheels in straight ahead
position and steering wheel centered. To adjust toe-in, loosen clamps
and turn adjusting sleeve or adjustable end on right and left tie
rods. See Figs. 2 and 5.
2) Turn equally and in opposite directions to maintain
steering wheel in centered position. Face of tie rod end must be
parallel with machined surface of steering rod end to prevent binding.
3) When tightening clamps, make certain that clamp bolts are
positioned so there will be no interference with other parts
throughout the entire travel of linkage.
Fig. 5:
Wheel Toe-In (Dimension A Less Dimension B)
1) Toe-out on turns (turning radius) is a check for bent or
damaged parts, and not a service adjustment. With caster, camber, and
toe-in properly adjusted, check toe-out with weight of vehicle on
2) Use a full floating turntable under each wheel, repeating
test with each wheel positioned for right and left turns. Incorrect
toe-out generally indicates a bent steering arm. Replace arm, if
necessary, and recheck wheel alignment.
1) Steering axis inclination is a check for bent or damaged
parts, and not a service adjustment. Vehicle must be level and camber
should be properly adjusted. See Fig. 6.
2) If camber cannot be brought within limits and steering
axis inclination is correct, steering knuckle is bent. If camber and
steering axis inclination are both incorrect by approximately the same
amount, the upper and lower control arms are bent.
Fig. 6:
Checking Steering Axis Inclination
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