Measuring Caster

[cjohnson6772]

Some background:
I have been looking the caster/camber gouges from Longacre or Amazon or DIY. I would like to have/make one of these setups and one of the hurdles is getting a set of turn plates which are expensive for a proper set or a cheap hacked solution like floor tiles with grease between them.

Caster is essentially measured by taking the difference between the camber values when the wheels are turned to the left a certain number of degree and the when the wheels are turned to the right the same amount. That is where the turn plates come in since this is almost always measured with weight on the suspension.

My question is this:
Even though the camber would be off with the frame on jack stands, would the difference in camber (i.e. caster) still be the same?

For those that are more interested, Hunter posted a white paper that derives alignment measurements and a good approximation for caster works down to caster = (180/pi) × (change in camber / change in steering angle). If using 20 degrees in both directions for steering angle, this works out to 1.43 x change in camber.