3D ALIGNMENT

1) Camber

Camber increases or decreases the tyre’s grip on the road by the wheel not being upright, when viewed from the front or rear. Correct camber is a design requirement and incorrectly set at best will cause tyre wear but at worse could seriously compromise the overall handling characteristics of the car – even making it dangerous.

2) Caster

Caster is the forward or rearward tilt of the steering axis, in reference to the vertical when viewed from the vehicle side.  Positive caster is where the steering axis is sloped towards the rear. Negative caster (not common) is where the steering axis is sloped towards the front.

3) Toe

Positive Toe is the leading edge of the wheels closer together. Negative Toe is the leading edge of the wheels further apart. Our advice would be not to refer to toe as toe-in. For example negative toe-in is toe out! Better to simply say the car has negative toe or is toed out.

4) KPI/SAI

Cars generally no longer have kingpins and hence the term KPI is outdated. SAI stands for Steering Axis Inclination and it will be referred to subsequently by this. When viewed from the front the SAI is the inclination of the strut top towards the centre of the vehicle, and in all cases is positive.

5) Thrust Angle

Thrust angle (other than zero) occurs when the individual rear toe values are unequal. The easiest example to imagine is for a car with a live rear axle (one piece) that has the axle fitted crocked in the body such that one rear wheel has toe-in and the other one has toe-out. Thrust line is an angle of the resultant drive direction compared to the vehicle centreline. Cars driven with high thrust angles may appear to ‘crab’.

6)Setback

Setback is the relative positions of the two wheels on an axle. Setback can be given in mm or as an angle i.e. degrees and minutes.

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