Caster changing?

[the_mayflower]

Hey guys/gals, I need a little help understanding something I'm seeing when setting caster. I jacked the car up, removed the spring, set the a-arms at ride height relative to the frame and then set caster(20° sweep method). After I was finished, I reinstalled the spring and set the car down. I verified ride heights and checked caster again, however it was 4° off of my previous setting? I'm a bit confused as I thought caster was based purely on geometry, so as long as the ride height is the same, the caster should be also?

[MasterSbilt_Racer]

It is geometry. The inclination of the line thru the ballpoints. If the frame is not at it's same angle relative to ground, it won't be the same.

[the_mayflower]

I did check each side independently so it seems I may have had the frame sitting at a different angle than when it is at ride height.. Thanks for the heads up, I'll check again with both sides at the appropriate ride height at the same time.

[stock car driver]

Do it with the springs in the car, tire psi set etc.