For all of you contemplating getting new wheels or tires you need to make sure the sizes are compatible with your vehicle. Normally you have to use a formula involving pi times the wheel diameter to make sure the outer tire surface is close to the same size as your original equipment tires or your speedo will be off or worse your new tires could rub in the wheel wells. I found a website that has calculators to determine proper tire size and tells you what your mph will be off if you are not exact. It also tells you how far in or out your tire surface will be from your fender based on your wheel offset if you are changing this.

The website is "The wheel and Tyre Bible" and is at http://www.carbibles.com/tyre_bible_pg2.html.

This allows quick input of your current wheel size and your desired new wheel size to tell you what you need to know. Have fun.

I like this one... Tire size comparer

+1 on this one. I use this one myself :)