Equation of a circle:
R^2 = x^2 + y^2
Dia R_ y y2 x2_ x
32 16 5 25 231 15.199 Rear tire trip point
26 13 5 25 144 12.000 Front tire trip point
3.199 Trip point difference
So on my car the beam trip points are 3.199" different than the wheel base. ie 111-3.2=107.8

And for Cudabin, I think he has 31 and 26 tires:

Dia R__ y y2 _x2___ x
31 15.5 5 25 215.25 14.671
26 13.0 5 25 144.00 12.000
2.671
And with a 108" wheel base, that changes the trip points to 108-2.67=105.3" (pretty close to my original estimate in post above).