Vintage Caster Measurement on 140 Series

I have found a lot of conflicting references for doing caster measurement when using a level gauge with a fixture for attaching it to the wheel rim (in this particular case a digital level gauge). The short form of the most common approach is for the right wheel, turn the wheel 20 deg to the right, zero the angle measurement, turn the wheel 20 deg to the left and read the angle measurement. Multiply this measurement by 1.432 and this is your caster measurement. Repeat for the left wheel.

Is this the approach being used by others?

I had my front cross member powder coated when I did my resto mod and since then I have been driving around with a single 1/8" shim at each adjustment point. To save me a lot of install / measure / remove / repeat does anybody have an estimate of the total shim thicknesses that they are running (and what your corresponding caster and camber is)? Or, as an alternative can anybody confirm how to interpret the shim graph that is in the factory service manual? I read the graph as saying measure your angle first then 'add or remove this shim thickness to get this angle change'. However, 2 x 1.0 mm does not get you the same change as 1 x 2.0 mm so ?? I am slightly confused.

I have never heard of the 1.432 measurement? I have a magnetic clip on alignment gauge that mounts to the wheel hub takes out the bent rim from the set up [it cost me $400 dollars, but very, very accurate], turn the wheel in, set to zero turn the wheel out, read the caster. Built racecars for 37 year it never let me down. There is no set shim stack, it all goes to where the wheels are when you check what you have, bumps and pot holes can bend the best of the chassis /cross members.

Some of the purpose built caster / camber gauges (Longacre for one as I recall) seem to have the correction factor built into the caster measurement scale on the bubble level. I note that they have a separate bubble level for the camber and caster measurement. They work exactly as you describe.

I am using a common general purpose electronic level for camber measurement that measures actual degrees. Most of the procedures (not all) that I have found use the zero on 20 deg out, measure angle change to 20 deg in and then multiply by 1.5 (or the slightly more precise 1.432). You are effectively measuring the camber at 20 deg out and 20 deg in and multiplying the difference to determine the caster. There is a formula that allows you to calculate the multiplication factor based upon the angles you use for the caster measurement. The 1.5 (1.432) factor works specifically for the 20 deg out / in technique. Since Volvo specifies the caster measurement at + and - 20 deg (which seems to be a very common spec) I was just using the 1.432 factor.

I recognize that there is no set shim stack. I had thought that the manufacturing tolerances might have been close enough that there was a 'general number'. However, yesterday after doing an initial camber measurement with equal shims under the 4 bolts I discovered I have -0.3 deg on the left and +0.8 deg on the right. So yes, bumps and manufacturing tolerances conspire against a 'general starting number'.