WHEEL ALIGNMENT 2B-9
GENERAL DESCRIPTION AND SYSTEM OPERATION
FOUR WHEEL ALIGNMENT CASTER Caster is the tilting 91 the uppermost point of the steering axis either forward or backward from the vertical when viewed from the side of the vehicle. A backward tilt is positive, and a forward tilt is negative. Caster influencesdirectional control of the steering but does not affect
tire wear. Weak springs or overloading a vehicle will affect
caster. One wheel with more positive caster will pull
toward the center of the car. This condition will cause the car to move or lean toward the side with the least
amount of positive caster. Caster is measured in degrees. CAMBER Camber is the tilting of the top of the tire from the vertical when viewed from the front of the vehicle. When thetires tilt outward, the camber is positive. When the tires tilt inward, the camber is negative. The camber angle is measured in degrees from the vertical. Camber
influences both directional control and tire wear.
If the vehicle has too much positive camber, the outside
shoulder of the tire will wear. If the vehicle has too much
negative camber, the inside shoulder of the tire will wear.
The first responsibility of engineering is to design safesteering and suspension systems. Each componentmust be strong enough to withstand and absorb extremepunishment. Both the steering system and the front and the rear suspension must function geometrically with thebody mass. The steering and the suspension systems require that the front wheels self-return and that the tire rolling effortand the road friction be held to a negligible force in orderto allow the customer to direct the vehicle with the least effort and the most comfort. A complete wheel alignment check should include
measurements of the rear toe and camber. Four-wheel alignment assures that all four wheels will be running in precisely the same direction. When the vehicle is geometrically aligned, fuel economy and tire life are at their peak, and steering andperformance are maximized. TOE
Toe-in is the turning in of the tires, while toe-out is the turning out of the tires from the geometric centerline or thrust line. The toe ensures parallel rolling of the wheels. The toe serves to offset the small deflections of the wheel support system which occur when the vehicle is rollingforward. The specified toe angle is the setting whichachieves 0 degrees of toe when the vehicle is moving. Incorrect toe-in or toe-out will cause tire wear and
reduced fuel economy. As the individual steering andsuspension components wear from vehicle mileage,
additional toe will be needed to compensate for the wear. Always correct the toe dimension last.
