I think some folks missed my point. True, the tire height and hence the diameter of the wheel/tire assembly determines the circumference. So indeed a 32 inch tire has the same diameter no matter what diameter rim it's mounted on. I was just trying to say if you get a larger rim and fit a tire on it with the same sidewall-to-sidewall width and aspect ratio as that mounted on a smaller rim, the resulting diameter would be greater. A tire's theoretical height in inches is calculated as follows:

Height = (Width x (Ratio/100) x .03937 x 2) + Rim Diameter

The width multiplied by the aspect ratio over 100 gives the height in millimeters, multiplying by .03937 converts to inches, and doubling this accounts for the fact that there's tire at the bottom and the top of the rim.

Didn't mean to say that the wheel diameter was the only variable in determining height, but by keeping the width and aspect ratio constant, height would vary as a function of rim diameter.