I'm runnin 35's on regeared stock D30 and C8.25 no probs. But i don't tend to put my foot in it very much, more of a finesse kinda wheeler... 38's though, locked on a D30... It'd have to be beefed up quite a bit, (sleved, trussed, tubes welded, ect ect.) to get me to trust that axle on the trail.