I have found online the possible missing link to tire sizing. 63360/(revolutions per mile)/pi
I have been comparing this formula to a variety of tire measurement posts, where the mfg supplies the rev per mile data at least, and damned if it doesn't come up with what folks are measuring.
A guy here at work just installed 35x12.5x15 Mickey Thompson MTZ's. I measured them at 33.5". I came back to my desk and looked them up. It states 601 revs per mile. So, 63360 (inches in a mile)/601=105.42429. That number gets divided by pi, or 105.42429/3.14159=33.55762. Again, this does require the mfg to actually provide that revs per mile data to work.
I have new tires coming this weekend, so I am going to do this again with mine, but for anyone who wants to include this calculation with their additions, as long as Eddie doesn't mind the additional data, I personally would be interested in how it works out against the tape measure.
Thanks. Been reading too damn many specs this week...