Rear caster error in measurement

[Ross Nicol]

Couldn't open the bump steer thread so had to slip in a new one. Have a read of my digital level thread in the tech chassis section and you will understand why I have posted this correction to measured rear caster on my car. What I thought was 7 degrees turns out to be 5.1 to 5.3 degrees. I humbly apologize for any inconvenience this may have caused.
Ross

[ChrisL]

I'm having the same problem with the bump steer thread but I believed my error message when it told me that it was my cache administrator

Anyway, I was never really sure how to measure rear castor. Is it along the plane of the reverse-a-arm or do you use an imaginary line drawn vertically along the centre of the upright or what? And is it relative to the ground or the chassis? There are many other options too and anyway, however you measure it, it changes dynamically doesn't it? Someone once even insisted that the term “rear castor” is meaningless because without steer there is no castor (but I think we all know what we mean).

[Ross Nicol]

Chris
I use my digital level on the machined area on the rear of the upright, it has 2 threaded holes.This surface is 90 degrees to the horizontal so makes the caster a direct reading ( when I read the correct scale that is).
Ross