Rim Width & Tire Bulge

I'm having a tire/rim fitting issue in my door car so I need to find out if any of you know the tire bulge difference on different size rims.
I have Hoosier 34.5/17.0-16 C2055 tires and they are mounted on Weld beadlocks that are 16x15". The bulge on this 15" wide rim is 21.3125".
What I trying to find out is what is the bulge with this tire on a 16" wide rim @6.5 LBS pressure. Hoosier says 21.4" in their catalog but I just want to make sure what it is in the real world. Any help would sure be appreciated.
I'm may have to buy a set of rims tomorrow or Monday (assuming Weld is open then).