Nope. I have found the formula to work flawlessly on any size, or aspect ratio. Why would it not? Compare your result to any tire company's data. It will agree. Just 2 examples:
245/45R19, ((245/12.7)*.45)+19=27.68", I looked on Tire rack and they are 27.6" or 27.7" depending on mfgr.
225/60R15, ((225/12.7)*.60)+15=25.63", again on T.R. they all say 25.6" .
Try it for any size and then look at the manufacturer's specs.
