If there are 272.5 rotations in a mile, and 5280 ft in a mile, then there are 5280 ft in 272.5 rotations. Divide 5280 by 272.5 gives us 19.4 ft/rotation.
That's the circumference of the wheel, and since c = πd, 19.4/π = d, d = 6.2 ft. The diameter of the wheel is how tall it is.
Does this help? Any questions?