go with the iroks, i had 39.5 bias iroks that lasted 2 years, 1 of which i was D/D and even when they were at 50% they still had mad traction in snow!! they slipped a little in rocks but it didnt slow me down much, i since have put 42" iroks on and they are awesome, but i miss my 39.5's, i think there are the best tire for the price and the perfect size for any application, these 42"s will be overkill on rocks, cant wait to get another set of 39.5"s
