I had the same problem when I took my car to the drag strip. My car would hop like crazy, which made me mad cause I wanted it to just grip or accelerate.. When I checked the air pressure, it seemed that one rear tire was slightly less than the other. When I adjusted the pressure and went for my next run, it didn't hop.... If you want.. U can change the rear shocks to Koni adjustables and you will feel a big difference in handling.. Hope that this helps.. Shihab..