The Dodge Challenger Message Board

I just found this Tyre Size Calculator:

http://www.tyresizecalculator.com/tyre- ... calculator

It seems to be very useable. What do you think?

I've been using that one for years :
http://www.rimsntires.com/specspro.jsp

It enables you to compare the size you want with the oem tire size, and tells you the difference at the speedometer.