Measuring Caster
 

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.

Re: Measuring Caster
 

I would assume no. If you want to work on your alignment with the frame on stands pull the springs and set the frame at ride height with the wheels on it.
Jimmy

Re: Measuring Caster
 

I read somewhere once that you can stack about a dozen sheets of wax paper, stacked together to make turn plates.You could make a grid on the floor before you start to get your turn angle the same side to side.

Re: Measuring Caster
 

I put soapy water on the floor under the tire (heavy on the soap). My alignment gauge says 15 degrees left, then 15 degrees right. I usually put tape on the floor at 15 degree marks.

I am not sure how accurate it is, but caster is usually a pulling/handling issue, not so much a tire wear issue. So as long as it is close and goes down the road straight without pulling, you are probably pretty good on these old trucks. If you are racing it, might want to take it to a shop.