What you can do is find out the diamater or whatever they do to multiply it by the tire.
I know a way to do it not with tires if you didnt already know this...
Its: First gear ratio x diff gears x t case low x 2nd case low(for some people)
Like me... 3.93 x 5.29 x 2.28 = 47.4 and I am runnin 37s...
Dont know if that helps at all....
Chris
