Originally Posted by Lumatic
There was a time, I assume, that torsion axles could have their caster and camber adjusted.
There is no caster adjustment on a trailer axle. Camber and tow-in are adjusted by bending the axle tube.
Caster is an adjustment on steerable wheels. It is what is known as "king pin angle". That is the number of degrees the upper and lower ball joints or whatever attachment method used, is offset from the vertical, upper being to the rear of the lower. That's what makes your steering wheel return to the center after going around a corner. It also causes your steering wheel to want to turn to one side or the other when going in reverse.
Camber is the number of degrees the top of the wheel is offset outward from the bottom of the wheel.
Tow-in is the amount the wheels on an axle point toward the center, away from an straight line. This us usually measured in inches, usually 1/8" or less.