go for 20 inchers, i have 18's and they aren't great for any trails, i run 22 inch mudders on my trails and rip but they don't slide, so i'd say 20 inchers, get some itp holeshot ( 6 ply) or some maxxis razr 2's or just plain razrs, also, my recomendation for a hardcore trailrider is beadlocks for rims, they will come back and save u some day, and they look cool, if u don't mind spendin the extra penny