Alignment: Description and Operation
DESCRIPTIONWheel alignment measurements describe the angular orientation of the wheel/tire assembly and the steering axis.
Caster, camber and toe are the three major, measurable alignment parameters.
^ Camber and toe affect tire wear and directional stability.
^ Caster affects directional stability without causing tire wear.
^ The values of caster, camber and toe change when a vehicle Reloaded and driven. Therefore, the specifications reflect the static measurement of alignment required so the vehicle will have an alignment when driven that is most favorable for tire wear and directional stability.
The vehicle should be prepped before checking alignment.
^ No driver or passengers should be in the vehicle.
^ All fuel and fluid levels should be full.
^ All tire sizes should be comparable to original equipment and set to specified pressure.
^ The vehicle should be configured to normal operating conditions.
CASTER
Caster is used to describe the vertical fore-aft tilt of the steering axis. This axis is defined by a line drawn through the centers of the spindle ball joints and is measured relative to the ground. Because of this, raising (or lowering) the rear without changing front ride height will subsequently decrease (or increase) the caster angle by the same amount the frame angle changes.
CAMBER
Camber is used to describe the vertical tilt of the wheel as viewed from the front.
^ Steering axis inclination (included angle) is the line to the axle drawn through the spindle ball joint when viewed from the front.
^ Included angle is a function of the spindle itself and does not change with changes in ride height or frame angles.
^ Scrub radius is the offset of the center of the tire tread at the ground to the point where the steering axis contacts the ground.
TOE
Toe-in and toe-out refer to the difference in the distance between the extreme front and extreme rear of the tires.
^ Toe-in (positive toe) occurs when the dimension taken at the front of the tires is less than that taken at the rear of the tires.
^ Toe-out (negative toe) occurs when the dimension taken at the front of the tires is greater than that taken at the rear of the tires.
^ If aftermarket equipment that significantly affects the ride height (such as snowplow, second unit bodies or tool boxes) is added, the toe might need to be adjusted. Toe should be maintained at the specified setting with the vehicle in the loaded condition experienced for more than 50 percent of use.
^ Toe should only be checked and adjusted after the caster and camber have been adjusted to specification. Refer to Front Wheel Alignment Specifications.
DOGTRACKING
This vehicle has a front tread that is wider than the rear tread. Front tread is the distance between the two front tires; rear tread is the distance between the rear tires. The illustration shows these differences.
When a vehicle with these tread differences is driven on a crowned road, the front tends to ride higher up the crown than the rear, making the vehicle appear to dogtrack, as illustrated.