Rally wheel size

The other problem with the diagram is you do not measure center to center on the lugs. You measure from the center of the first to the far edge of the second lug.

Remember this is an approximation so with 7/16 lugs you will get a slightly smaller number than with 1/2" lugs. But if you got 4.25 center to center then for sure you have a 4 1/2" bolt circle.