[tman]

go to tirerack.com and put in your current wheel and tire size, and the wheel size your going to. They'll tell you the updated tire dimensions so you can order the same overall size, you follow what I'm saying? Increase wheel size, the tire size shrinks.

You can also look up what the factory 16 inch wheels had on it to, go to tirerack.com and pretend like youve got the ultra and it'll give you the adjusted size.