Auto Wheel Alignment Specificationsby Teri Olcott
Wheel alignment refers to the vertical and horizontal position of a car's wheels in relation to the body of the car. Rough roads and potholes can cause wheels to go out of alignment. When performing wheel alignment, technicians and owners check four angles that may require adjustment to make sure the tires wear evenly. Wheels that are out of alignment by just a few degrees can cause tires to wear out before they should.
Camber refers to the angle of the front and rear wheels when viewed from the front of the car. Wheels that lean inward have a negative camber; wheels that lean outward have a positive camber. Camber is measured in degrees. Tires that show excessive tread wear on either the inside or outside of the tire usually need camber adjustment.
Caster refers to the angle between two pivot points, created when the steering wheel turns the front wheels. A ball joint and a strut mount control how well the wheels turn. Caster is measured in degrees from the front of the vehicle. When the top pivot leans toward the back of the car, the caster is positive. A pivot that leans towards the front of the car has negative caster. A car that drifts or pulls to one side may need caster adjustment.
Toe refers to the measurement between the front side of two matching tires and the back side of two matching tires. If the front sides of the tires are closer than the back sides, the tires are said to toe-in. If the back sides of the tires are closer than the front sides, the tires are said to toe-out. Most cars are adjusted slightly toe-in which gives the car a better feel at high speeds. A car with feathered wear to either both front tires or both back tires may need toe adjustment.
Thrust angle, also known as four-wheel alignment, refers to the angle of the front axle in relation to the rear axle. Thrust angle alignment ensures that all four tires are aligned to each other. Cars with independent suspensions can usually benefit from thrust angle alignment.
- detail of a car tire image by Albert Lozano from Fotolia.com