The angle between upper and lower ball joints in side view, about which the wheel turns.
It is measured in degrees, and is positive when this intersection lies ahead of the projected tyre centre on the ground in the direction of travel.
This is the change between design and any suspension position.
The change in caster as the wheel moves up and down from full jounce to full rebound. Caster gain is measured in degrees per millimetre.
The side view distance between the point where the steering axis meets the ground and the centre of the tyre contact patch. It is measured in millimetres.