air suspension

Air suspension is used in place of conventional steel coil, leaf or torsion springs in heavy vehicle applications such as buses and trucks, and in some passenger cars. It is widely used on truck trailers and trains (primarily passenger trains).

The purpose of air suspension is to provide a smooth, constant ride quality, but in some cases is used for sports suspension. Modern electronically controlled systems in automobiles and light trucks almost always feature self-leveling along with raising and lowering functions.