Alignment of the front wheels is essential if your car is to go, stop and turn as designed. Alignment can be altered by collision, overloading, poor repair or bent components.
If you are diagnosing bizarre handling and/or poor road manners, the first place to look is the tires. Although the tires may wear as a result of an alignment problem, worn or poorly inflated tires can make you chase alignment problems which don't exist.
Once you have eliminated all other causes (always check and repair front end parts BEFORE wheel alignment), unload everything from the trunk except the spare tire, set the tire pressures to the correct level and take the car to a reputable alignment facility. Since the alignment settings are measured in very small increments, it is almost impossible for the home mechanic to accurately determine the settings. The explanations that follow will help you understand the three dimensions of alignment: caster, camber and toe.
Caster is the tilting of the steering axis either forward or backward from the vertical, when viewed from the side of the vehicle. A backward tilt is said to be positive and a forward tilt is said to be negative.
Camber is the tilting of the wheels from the vertical (leaning in or out) when viewed from the front of the vehicle. When the wheels tilt outward at the top, the camber is said to be positive. When the wheels tilt inward at the top the camber is said to be negative. The amount of tilt is measured in degrees from the vertical. This measurement is called camber angle.
Toe is the turning in or out (parallelism) of the wheels. The actual amount of toe setting is normally only a fraction of an inch. The purpose of toe-in (or out) specification is to ensure parallel rolling of the wheels. Toe-in also serves to offset the small deflections of the steering support system which occur when the vehicle is rolling forward or under braking.
Changing the toe setting will radically affect the overall "feel" of the steering, the behavior of the car under braking, tire wear and even fuel economy. Excessive toe (in or out) causes excessive drag or scrubbing on the tires.