I spent a number of years training techs on alignment and alignment equipment. People love to say that changing the rear height does all this hocus pocus on front caster, you can draw it on paper, or on a computer so it must be true. Truth is it isn't true. I've tested a number of cars, not enough to have a scientific study, but more than one. Specifically my 99 with changes as big as 3.5" and had almost NO CASTER change on the front wheels! Or NO CASTER change at all. Now I could have made a mistake, but I didn't, I did the roll back on my 99 about 20 times with just two rear heights. stock and 2" higher, I only checked it once maxed out at 3.5" on the airlift 1000's. At 2" there was no change, or .1 degrees, at 3.5" it did change, but that was 2-1/2 years ago, or more, so I don't remember the amount. I think it was about .2 -.4 degrees. Now if you look up some specs for older chevy trucks, they gave you caster specs based on rear ride height. That is to say they wanted you to CHANGE caster based on rake, not necessarily that it would be changed. MBZ and some other manufacturers base ALL their specs off of ride height, both front and rear. I tried changing the ride height on an E36 and an E39, not huge amounts but I did get small changes in Caster reading but the change was small, maybe 1/2 to 3/4 of an inch.
I'm a huge fan of science, but like my Frame man used to say, the parts don't lie.
For our purposes(3rd Gen) I think it is a negligible consideration for overall caster readings.
I should have saved all those readings... I should'a ....
