Camber

The diagram of the car below shows the tires set at positive and negative camber angles. Zero camber is where the tyres are exactly vertical. The camber is always measured from the vertical. When the car leans in a turn it is important that the tires do not lean with the chassis or else the camber will change. Keeping the camber near to zero under all conditions is the primary goal of modern suspension systems. Camber angle is very critical in determining the handling characteristics of the car.

Castor

The castor angle is the angle between the steering pivot axis and a vertical line as shown in the diagram below. Positive castor is illustrated, where the upper end of the steering pivot axis tilts towards the rear of the car. Most cars have positive castor. Castor causes castor trail, which is force imbalance at the tyre contact patch. This force twists the tyre tread and creates a torque around the point where the steering axis intersects the tyre contact patch. The greater the castor, the more castor trail is present. The torque increases with castor and so does the steering effort. The self centering effect of the tyres caused by this torque also increases, which improves straight line stability and driver feel of the tyres. Less castor reduces tire scrub while cornering, but reduces stability and feel.

Toe-in / Toe-out

The diagram below shows how to measure toe-in or toe-out. The measurements are taken at the tyre tread and are given in inches. A small amount of toe-in is the setting for most cars. Toe out is sometimes used, particularly on front wheel drive cars. The rear suspension can also have a toe setting on independent suspension systems. At the front tyres, toe-in improves straight-line stability, while toe-out will help steer a car into a turn by reducing corner entry understeer slightly. Toe-out causes a car to wander in a straight line and is not recommended.