This angle is called road crown. Road crown also can cause a vehicle to pull toward the right. Therefore, alignment angles must compensate for it. Slightly more positive camber on one of the front tires will correct road crown.
ALIGNMENT GEOMETRY
The proper alignment of a suspension/steering system centers on the accuracy of the following angles.
Caster
Caster is the angles of the steering axis of wheel from the vehicle, as viewed from the side of the vehicle. The forward or rearward tilt from the vertical line (Figure 45-2) is caster. Caster is the first angles adjusted during an alignment. Tilting the wheel forward is negative caster. Tilting backward is positive caster.
Caster