Camber, the slant of the tire top from true vertical, improves both tire life and handling by distributing vehicle weight evenly across the tire tread. Camber also enhances directional stability to some extent. The easiest way to comprehend camber is to look at the centerline of the tire from the front of the vehicle. When the tire centerline is perfectly vertical like a plumb bob string, the tire has zero camber.
Tilting the tire centerline outward from the vehicle creates positive camber, tilting it inward makes negative camber.
Typically, vehicle manufacturers specify a slightly positive static or stationary camber value.
Because camber directly affects tire wear, incorrect camber causes premature tire wear.
Elsewhere in this service section, we emphasized that two angles-camber and caster-can cause a vehicle to pull. Camber problems create more pull complaints than caster does.
Unfortunately, technicians either forget or overlook camber's influence on steering and tracking.
First of all, changing camber actually changes the direction of the vehicle.
Second, when right and left caster values are equal or nearly equal, the vehicle will pull toward the side having the greatest amount of positive camber.
Picture the bicycle rider who leans to the left. Leaning in that direction increases positive camber so the bike tracks toward maximum positive camber-the left side.
Third, automakers generally specify the same camber values for both sides of the vehicle. Some manufacturers allow side-to-side camber variations to compensate for road crown and/or the weight of the driver.
But right and left camber specs are usually well within one-half degree of each other.
Always watch those footnotes in wheel alignment specification books. Some automakers require a certain amount of weight on the driver's side of the vehicle during the procedure to check camber.
Abnormal camber conditions
Besides a pull, tire wear is an excellent clue to an excessive camber condition (See accompanying illustrations). Excessive positive camber causes scuffing or shoulder wear on the outside of the tire. Too much negative camber creates the same wear patterns on the inside of the tire.
Basically, anything that affects the tilt of the tire centerline changes camber. For example, incorrect ride height and low air pressure make a major impact on camber. If you doubt it, watch the camber reading's reaction when you pull down or lift the front of the vehicle. Then watch what happens to camber when you bleed air out of a tire.
Factors such as overloading, fatigued or broken springs, incorrect springs or a sagging front frame crossmember change camber by altering ride height.
Furthermore, sloppy control arm bushings, worn upper strut mounts and worn ball joints also affect camber.