The springs used on todays vehicles are engineered in a wide variety of types, shapes, sizes, rates, and capacities for each kind of automobile and truck depending on your vehicles suspension design. Leaf springs (both multiple and single leaf), coil springs, and torsion bars are the most commonly used springs. A certain kind of spring, called air spring, can also keep your truck off the ground and determine ride height, which in turn influences steering and suspension(See Fig.10-1).