This would actually be a great question to post...you should toss it up as a seperate thread!

From what I can find most tires give the range of rim they will fit in the spec discription and that is usually a 2in variance. It seems that a 225 is right at the upper limit of what will work well on a 7in wheel. But that is just what I have found poking around the net, so I could be off.
Mark