What tire pressure are you running and what load range are they? That could be the reason for the rough ride. A lot of people think that the PSI stamped on the side of the tire is what they should be inflating to. That number is the maximum PSI at the specified load. Also, once you go with a bigger tire, the PSI on the door jam is no longer valid. For a load range C tire, you'll only need about 26 PSI to support the vehicle for a 33" tire.