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