Alignment of the front wheels is essential if your vehicle 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, unload everything from the trunk except the spare tire, set the tire pressures to the correct level and take the truck to a reputable alignment facility. Since the alignment settings are measured in very small increments, it is almost impossible for the owner/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. Changes in caster affect the straight line tendency of the vehicle and the "return to center'' of the steering after a turn. If the camber is radically different between the left and right wheels (such as after hitting a major pothole), the truck will exhibit a nasty pull to one side.
Caster is adjustable through the use of shims, which reposition the suspension components in the correct direction.
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.
Camber affects the position of the tire on the road surface during vertical suspension movement and cornering. Changes in camber affect the handling and ride qualities of the truck as well as tire wear. Many tire wear patterns indicate camber related problems from misalignment, overloading or poor driving habits.
Camber is adjustable on Pick-Ups and 4Runners through the use of shims; if the measurement is out of specification, the bent or damaged component(s) must be replaced.
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 insure 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 subjected to hard braking.
Changing the toe setting will radically affect the overall "feel'' of the steering, as well as the vehicle's braking ability, tire wear and fuel economy. Excessive toe (in or out) causes excessive drag or scrubbing on the tires.
Toe is adjustable on all vehicles covered by this guide, and is generally measured in inches or degrees. It is adjusted by loosening the locknut on each tie rod end and turning the rod until the correct reading is achieved. The left and right rods must remain equal in length during all adjustments.