Wheel alignment

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Wheel alignment is part of standard automobile maintenance that consists of adjusting the angles of the wheels so that they are set to the car maker's specification. The purpose of these adjustments is to reduce tire wear, and to ensure that vehicle-travel is straight and true (without "pulling" to one side). ^[1]

[edit] Angles

There are two types of angles that should be adjusted regularly during the life of an automobile. The first type is called the 'primary angles' and second type is called 'secondary angles'.

Within primary angles, there are three adjustment parameters involved on each axle in order to properly align a vehicle. These adjustments are camber, caster and toe. On some cars, there may only be the ability to adjust for one or two of the parameters.

These three parameters can be further categorized into front and rear, so summarily the parameters are:

Front: Caster (left & right)
Front: Camber (left & right)
Front: Toe (left, right & total)
Rear: Camber (left & right)
Rear: Toe (left, right & total)
Rear: Thrust angle

As for the Secondary Angles, the adjustment parameters are quite numerous. They are:

SAI (left & right)
Included angle (left & right)
Toe out on turns (left & right)
Maximum Turns (left & right)
Toe curve change (left & right)
Track width difference
Wheel base difference
Front ride height (left & right)
Rear ride height (left & right)
Frame angle

Setback (front & rear) is often referred as a wheel alignment angle. However setback simply exists because of the measuring system and does not have any specification from car manufacturers.

A camera unit (sometimes called a "head") is attached to a specially designed clamp which holds on to a wheel. There are usually four camera units in a wheel alignment system (a camera unit for each wheel). The camera units communicate their physical positioning with respect to other camera units to a central computer which calculates and displays how much the camber, toe and caster are misaligned.