Wheel alignment

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A 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 maximum tire life and vehicle-travel that is straight and true when driving along a straight and level road, although most machines and the technicians who use them set the alignment to adjust for crowned roads, as well as correct tracking when driving on turns.

There are 2 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. It is important to note that 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.