Think link is pretty cool also if you want to see all the brands available for the sized tyre you're after.
http://www.1010tires.com/TireSizeCal...mp;vehicle=yes
There's also a web site that tells you, if you're planning on going for a larger diametre, how much the speed of the car will vary due to the differences and hence whether it's legal or not, recommended or at least you'll be aware of the difference & therefore adjust your speed to avoid getting your picture taken
I'll try to find it in my failed dewy system of favourites.