Wheel and Tire Forum
Interactive wheel and tire combination calculator.
As an example, here is a side by side comparison of my 17x8 RH AD Cups and my soon to be shod 17x7 Porsche 993 Cup IIs:
The Cup IIs shod with 205/50s are actually 4mm larger in profile, but .8"(20mm) narrower in tread width.
But in weight...