I posted this earlier here in a thread about Riderites.
"I have a 04 GMC 3500 CC Dually. I have both Trailair Pin box and Firestone Riderite air bags. I orginally put the Trailair box on and it greatly improved the ride, but still had a lot of chucking, Trailair sent me another air bag for it, and it improved the chucking somewhat. Don't ask me why or how, but it did help some, at least the chucking that is left is tolorable. I was still getting a harsh bounce, banging or ride when hitting a bump or rough places in the road. With my 5er loaded and ready for the road, my truck was not touching the overload springs. It was about 1/2 to 1" from the overload spring brackets, so that when I hit the rough places, dips and such, I contacted the overloads and got a harsh bump. I installed the Firestone riderites and then I removed the overload spring brackets from the frame, easier than removing springs and changing "U" bolts. Now I carry about 25-30 lbs. air presure when loaded with 5er and I don't get the harsh banging and noise when hitting the bad spots in the road. The Ride rites are now my overloads. It still rides like it has 2700# in the bed, plus extra 60 gal fuel tank, but that is a fact, I do have that much in the bed. But the ride is greatly improved. Well worth the change to us."
Jim