I am switching to 13" tires and wheels this season. I have two sets (of 4) wheels and tires up for sale.
1990 Miata 14" alloy wheels with 205/55-14 Kumho Victoracer tires. The tires would only be good for an event or two. Just enough to try R-compound. $100. Photo at: http://www.pbase.com/mx5/image/69617936
1994 Miata 14" alloy wheels with 205/55-14 Hoosier autocross tires. I used these last season, treated them with Formula V, shrink wrapped them, stored them in my house inside a plastic bag. $300. Photo at: http://www.pbase.com/mx5/image/69617936
-Cheers,
-Wayne