I drove it in a rainstorm for the first time since I bought it in March (we're in a drought here in Austin TX) and the thing was hydroplaning all over the place. Had to go 40 mph on the freeway to keep the rear end from shifting around. Got home and looked at the rear tires, right rear is bald from on the inside half. Left rear is also worn from the inside out, but not as bad as the right. What could be causing this??? Is this normal wear for an S55?