The other night, I was wanting to compare wheel sizes and back spacing on some wheels I was planning to buy for my T Bucket project. I knew I had one book marked, but couldn't find it. So, a Google search found this one. It's easy to use. Input tire size and wheel dimensions and it shows, in side profiles, the relationship of both wheel and tire dimensions. It also gives suggested rim sizes. It helped me and I thought I'd share. I don't know if it does bias tires, but you can't have every thing. http://www.rimsntires.com/specspro.jsp