What is Alignment and Why Does it Matter?
A wheel alignment refers to the adjustment of the angle of the wheels in relation to the road. Alignment is important for facilitating proper handling, tracking, and reduction of tire wear. It is a good idea to get your car regularly aligned, especially if your car is no longer tracking straight, your tires have uneven wear, or your wheels recently hit a large object (curb, large pothole, etc).
There are generally three things mechanics are looking for when performing an alignment:
Camber is the inward or outward angle of the tire when it is viewed from the front of the vehicle. If the wheel sits perpendicular to the road, this is 0 degrees of camber. If the top of the tires lean inward, this is negative camber. If the tires lean outward from the vehicle, this is positive camber. Some cars (e.g. Porsche) will have higher negative camber to aid in cornering.
Toe is like camber, but rather than viewed from the front of the vehicle, it is viewed from above. It is is the inward and outward angle of your tires when seen from a bird’s-eye view. Positive toe or toe in is when the front of your tires are angled inward (similar to being pigeon toed). Cars usually have positive toe at rest and as the car speeds up, the front of the tires tend to move outward leading to a more neutral toe.
Negative toe or toe out is when the front of the tires are pointing outward.
Caster is the angle of the steering axis in relation to the vertical axis (or pivot line) of the wheel when viewed from the side. Positive caster is the when the suspension axis is behind the vertical line and negative caster is the opposite direction.
Caster is important for self-centering or on-center feel of the steering wheel. Improper caster may result in having to actively “steer” the wheel back to center.
Which factors are adjustable on your car can vary: for example rear toe and camber are typically not adjustable. Same can go for caster. Front toe is almost always adjustable.
An alignment is important for proper handling and tire wear. Here is a great video that summarizes these principles.