Caster is measured by turning the spindle right and left 20 degrees each way from straight ahead, and measuring the camber change as it turns. It's pretty simple to do if you have a set of turn plates and a magnetic caster/camber gauge with calibrated level bubbles. Without that equipment, the simple way is to install a wedge on both sides, and take a test drive. As above, too little caster makes a vehicle wander and refuse to self-center after a turn, too much makes steering effort increase, and tires will wear in a feathery pattern due to excessive scrub in turns.
Jerry
