Air suspension on trailers/semi-trailers ensures not only gentler treatment of the load being hauled but also less wear and tear on the roads. This aspect is of growing importance as traffic volume becomes increasing dense. As a rule, each axle has two air springs. In multi-axle combinations, one axle is frequently provided with an axle-lifting device to protect the tires on empty runs or when the vehicle is only partially loaded. Convoluted air springs usually are used for raising and lowering lift axles.
