If it is bouncing up and down, that is usually shocks. Depending on how long and severe it has been going on, it may have caused flat spots in the tires. I am on my third Silverado 1500 ('05, 08, and now '15). The '05 road a little rougher probably due to the torsion bar suspension. When they switched to coils on the '08+ it was a major improvement. What load range are your tires? If you don't haul heavy loads and don't tow; I would be looking at some P series tires.