Gmasters wrote--"I am replacing the existing ones on my car because I thought they were bad. I was always under the impression that they spring back up but is this model just for dampening and it uses the coil to bring back up...this doesn't sound right to me. Any help would be greatly appreciated. These are my first set of shocks I am replacing so any info is helpful. Thank you."
As another poster wrote - the reason for the the gas is to keep the oil inside from foaming which happens when the shocks are put through rapid cycles making them ineffective. The gas inside has nothing to do with lifting the car--that's the job of the springs--regardless of whether there are gas filled shocks or not. In a subsequent post Gmasters asked if there's a way to test shocks -- yes -- the old bounce test. If shocks are good they will control the bounce of the car if you push the car down hard (do each corner separately). A good set of shocks will allow the car to spring back up and then settle down to normal height. Bad shocks will allow the energy in the springs to cause the car to continue bouncing up and down through a few cycles till the spring's energy is spent. With the shock removed there should be heavy resistance to expanding and contracting the shock by hand with no "dead" spots. -- Dave