15x8 like the other guys said.. it will keep your rim farther away from rocks and other sharp objects. Also with the wider rims (15x10) you'll get mud and sticks jammed down into the bead causing a slow leak... that happened when I went wheeling with my stock tires and wheels in my YJ. Tire was flat the next day and I had to get it cleaned out at a tire shop.
Registered Nurse Jeep Club Member #1 (I think...)
Verse 36: And He said to them, "But now, whoever has a money belt is to take it along, likewise also a bag, and whoever has no sword is to sell his coat and buy one.