CARL,
As BOB stated, RON COON sells a lot of different tire/rim combos, cool part, the tires have the sizes listed right with the tires, and along with the size in actual "inch" listings, they also have them in "mm" listing (which in 1/25 scale basically relates to the actual "inch" size of the real tire.) So if you are trying to "replicate" a 30 inch tall tire, look for a 30mm size resin tire, want a 28 inch tall tire, look for 28mm, etc.
GOOD LUCK on your hunt...
DJ
P.S.- I use a lot of RON'S Hoosier Dirt Boss tires and his T30 tire (which is the bigger Hoosier) YOU'LL LIKE EM!!!!