Suspension Technology Industries, “STI”, used the technology learned during the early development of air suspensions to design an air suspension specifically built for smaller trailers. These trailers normally carry cargo such as horses, automobiles, electronics, living quarters or any of the thousands of uses for bumper pull and goose neck trailers. Most air suspensions will consist of air springs (bags), an axle, a structure to hold the axle that allows up and down movement of the wheel and brackets to attach the suspension to the trailer frame.

STI’s approach to the suspension design was to keep everything as simple as possible. The axle was eliminated and replaced with a 3” x 4” cross tube that does not require additional cross members when mounting to the trailer frame. The cross tube is attached directly to the trailer frame and actually adds to the strength of the trailer. Nothing on the suspension projects up into the area above the bottom of the trailer frame.

At each end of the cross tube there are rotating shafts with swing arms attached to one end. These swing arms hold the wheel spindle. They are not connected from side to side making the suspension an independent wheel suspension. The shaft is mounted in housings that are attached to the cross tube and rotates in composite bushings. The bushings are very low maintenance and only require greasing at the same time that the wheel ends are given their normal service maintenance. Unlike suspensions that have a separate axle, the swing arms on the STI unit may be removed one side at a time in the event a wheel spindle is damaged.

A small but rugged trailing beam is attached to the swing arm shaft with “U” bolts. This beam supports and protects the air spring that provides cushion for the ride. The beam is designed to provide the same ground clearance with or without air in the air spring. The air spring is manufactured like a tire. Fibers are wound to shape and covered with a rubber coating. They are very rugged and normally last for years. Air springs also have a bumper mounted inside that acts as a stop when the system has no air. The trailer can actually be moved short distances when required on the bumpers without causing damage to the suspension

Wheel end equipment for all capacities is available. The most popular units are the 7k, 8k, and 10k. A full selection of brakes is also available including the electric and hydraulic drum, the hydraulic disc and the STI Cargo-Max hydraulic disc.

STI developed our hydraulic disc brake equipment, Cargo-Max, for 10K and 12K LBS air suspensions. The Cargo-Max allows maximum space usage of the inside of the trailer by mounting the disc brakes inside the profile of the wheel and tire. The width of the trailer structure can be larger without increasing the overall width of the axles. This will allow two 10K or 12K axles to be used in place of three 7K or 8K axles without compromising inside cargo space and actually gaining interior area