yeah i agree start w/ 31s and build your rig from there!!! if you learn to read trails right a 31 will do just fine. then move up when u want harder lines!!! look into lockers second, everybody hates to be stuck b/c only 2 wheels are pullin b/c there both off the ground or just spinning!!!! and just remember the bigger tires and lower the gear u run a better chance of breaking axles. well thats my opinion but you know what they say about opinions!!! #1 rule have fun with it