My tire, the BFG TA/KO, specifies 6.5-8.5" rim width for the 30x9.5R15 size. BFG specifies 6.0 -7.0" rim width for their very similar 235/75R15 size. I"m on 7" wheels and will move up to one of these two sizes. But, a lot of guys do use narrow rims and seem to get away with it. The big problem, if I remember rightly, is that tires tend to come off narrow rims when aired down and on-the-road handling can get squirrely unless the tire pressure is high. The good news is that a 9.5" tire probably won't need a wheel with reduced backspacing (negative offset) to avoid rubbing.