What year Jeep. If you have a 96' and older you can probably get away with the 30's, but on the 97 and newer you will have to get at least a 2' lift to fit 30's. As far as 31's, I would seriously look into either a 3" lift or the best, 4.5" lift. Again, it all depends on the model year. Yes, 31x10.5R15 will fit on the stock rims, but recommend going with at least a 15x8" rim, tires will look better, on the 7" it has a tendancy to look like a balloon due to pulling in the bead.