Someone posted it a few months back. You enter your stock tire size, then the size you are planning on installing, and it compares the outer diameter difference. I need to upgrade my truck tires and that is one valuable resource.

www.tirereack.com go to spec under the tire you're looking at.

No thats not it.

I'm speaking of a very simple web site that put a graphical, 2D wire representation of the tire diameter on the screen, and when you entered the tire specs of the tire you were considering, it would overlay the new tire on the old and showed the difference in outer diameter between the two as a percentage.

It would take forever to look up that info on the Tire Rack site.

zing.... http://www.miata.net/garage/tirecalc.html

Schweet! Thanks Kev.

Kevin, is there no end to your usefulness? :D