caster may be adjusted by using wedges or shims,
eccentric cams, or adjustable struts.
Negative caster (fig. 8-48) tilts the top of the
steering knuckle toward the front of the vehicle. With
negative caster, the wheels will be easier to turn.
However, the wheels tend to swivel and follow
imperfections in the road surface.
Positive caster (fig. 8-48) tilts the top of the
steering knuckle towards the rear of the vehicle.
Positive caster helps keep the wheels of the vehicle
traveling in astraight line. When you turn the wheels, it
lifts the vehicle. Since this takes extra turning effort.
the wheels resist turning and try to return to the
Camber is the inward and outward tilt of the wheel
and tire assembly when viewed from the front of the
vehicle. It controls whether the tire tread touches the
road surface evenly. Camber is a tire-wearing angle
measured in degrees. The purposes for camber are as
To aid steering by placing vehicle weight on the
inner end of the spindle
To prevent tire wear on the outer or inner tread
To load the larger inner wheel bearing
Positive and negative camber (fig. 8-49) is
measured from the true vertical (plumb line). If the
wheel is aligned with the plumb line, camber is zero.
With positive camber, the tops of the wheels tilt
outward when viewed from the front, With negative
camber, the tops of the wheels tilt inward when viewed
from the front.
Most vehicle manufacturers suggest a slight
positive camber setting from a 1/4 to a 1/2 degree.
Suspension wear and above normal curb weight
caused by several passengers or heavy loads tend to
increase negative camber. Positive camber counteracts
Toe (fig. 8-50) is determined by the difference in
distance between the front and rear of the left and right
side wheels. Toe controls whether the wheels roll in the
direction of travel. Of all the alignment factors, toe is
the most critical. If the wheels do NOT have the correct
toe setting, the tires will scuff or skid sideways. Toe is
measured in fractions of an inch or millimeters.
TOE-IN is produced when the front wheels are
closer together in the front than at the rear, when
Figure 8-49.Camber angle.