A vehicle is said to be properly aligned when all suspension & steering components are sound & when the tire & wheel assemblies are running straight & true. Just as a person's shoes wear evenly across the heels & soles if that person's weight is evenly distributed over his feet as he or she walks, tires will wear evenly if the vehicle's suspension system allows them to meet the road evenly. Proper alignment is necessary for both even tread wear & precise steering.

You need an alignment when you notice uneven front or rear tire wear or changes in your vehicle's handling or steering response (i.e. pulling to one side). Many vehicles today are equipped with rear suspensions that can be adjusted for alignment. If this is the case, your vehicle may need a "front-end" alignment or a "four-wheel" alignment, depending on the symptoms you are experiencing.