The main advantages of an air spring over its steel leaf and coil
counterparts are variable load-carrying capability, adjustable spring
rate, user-friendly height control, low friction action, and road-friendly suspension increasing the pavement life.
The load an air spring carries can be adjusted over a wide range, without changing the air spring height, simply by changing the air pressure. Traditional steel springs need to be replaced if the height must be maintained. In addition to changing the load-carrying capability, a change in air pressure will also afford the benefit of changing the spring rate without changing the height and without a significant change in the natural frequency. Steel springs exhibit one spring rate for a given height and, once again, will need to be replaced if the height must be maintained.Using air pressure from the compressor, the air spring height can be maintained by a closed-loop control system or adjusted to the other desired heights. This allows for "load leveling" and "squatting" capabilities that steel springs cannot offer. Because there is a flexible rubber member separating the rigid attachment points to the frame and suspension, there is freedom to move about all six degrees of freedom without the resistance and squeaks experienced by the rigid interactions characteristic of steel leaf and coil springs.