Try this then:
How to find your revs/per mile:
Formula:
x = The loaded tire radius in INCHES from ground to center of axle.
63360 / ( 2 * pi * x )
Example:
63360 / ( 2 * pi * 16.5 )
(copy/paste in google search bar)
Answer:
63 360 / (2 * pi * 16.5) = 611.154981