Alignment Basics: Aligning a car or truck involves the adjustment of the vehicle's suspension—not the tires and wheels. The direction and the angles that the tires point in after the alignment is complete are critically important. There are five factors involved in setting the alignment to specification: caster, camber, toe, thrust and ride height. The following brief discussion of each aspect will help you understand the process and spot potential problems.

Caster: Caster is the angle of the steering axis (the part of the suspension that supports the wheel and tire assembly). Viewed from the side of the vehicle, an imaginary line drawn between the centers of the upper and lower ball joints forms an angle with true vertical; this is defined as the caster. The illustration to the right shows whether this angle is referred to as positive or negative. Caster is important to steering feel and high-speed stability.

Camber: Viewed from the front of the vehicle, camber describes the inward or outward tilt of the tire. The illustration below shows whether this tilt is referred to as positive or negative. The camber adjustment maximizes the tire-to-road contact and takes into account the changes of force when a vehicle is turning. Camber is the one adjustment that can be set according to driving habits. If you drive more aggressively when cornering, more negative camber can be set. If you drive on highways and do very little hard cornering, more positive camber can be set.

Toe: Viewed from above the vehicle, toe describes whether the fronts of the tires are closer (toe-in) or farther apart (toe-out) than the rears of the tires. The illustration below shows this relationship. Toe settings vary between front and rear wheel drive vehicles. In a front wheel drive vehicle, the front wheels try to pull toward each other when the vehicle is in motion, which requires a compensating toe-out setting. A rear wheel drive vehicle works just the opposite, necessitating a toe-in setting. Stated differently, the toe is set to let the tires roll in parallel (at zero toes) when the vehicle is in motion.

Ride Height: By now you may have concluded that poor tire wear and misalignment are closely related. That, of course, is true. But what can be done to minimize this condition? It turns out that many of these misalignment conditions can be easily “read” by your tire dealer; and they can recommend the appropriate solution, which will be “get an alignment.” For your assistance, the following troubleshooting guide will help you see what your tire dealer sees. Armed with this knowledge you can check your tires every so often; a knowledgeable glance at the parking lot can pay big dividends.