July 2018 | VehicleServicePros.com 29
Shock absorber
Shock absorbers work basically the same in an
air suspension as they do in a traditional spring
suspension. Th eir purpose is to dampen the eff ects
of the springs, limiting suspension movement to
create a controlled motion. Without shock absorbers,
the vehicle would simply bounce on its springs
in an uncontrolled manner, leading to very poor
handling and stability.
Shock absorbers sometimes
serve a dual purpose in
air suspensions, however. If
the vehicle “bottoms out” or
reaches the limit of suspension
travel, the shock absorber can
act as a bumper stop to prevent
the suspension from traveling
beyond that limit and damaging
the air springs.
“Shock absorbers for air
suspensions would be more
likely to include a hydraulic
rebound stop feature, as they
typically also function as the
suspension travel limit,” says
Gerald Anderson, engineering
manager at Gabriel HD.
Gabriel is an aft ermarket and
OE manufacturer of shocks
and struts for light and heavy
duty trucks.
Potential issues
Like most moving parts of a
vehicle, suspension components
can eventually break
down.
“Air springs are a consumable
item as they do wear over
time,” says David Brinkman,
category director of suspension
products at Stemco.
“Possible issues can be over-
or underinfl ation and damage
from road debris. Another
issue is worn or damaged
shock absorbers, which will allow the suspension
to travel beyond design limits.”
Stemco is a manufacturer of commercial vehicle
wheel end, braking and suspension components,
as well as tire and mileage solutions.
A ride height that is outside of the manufacturer’s
specifi cation can also cause problems with air
suspensions. Drivers should pay attention to how
the truck rides and handles, as any change could
indicate a potential issue.
“Poor ride quality could be an indicator that
there is an issue that needs to be addressed,” says
Hendrickson’s Hampson. “For instance, it could
indicate that the suspension ride height is set
incorrectly, or that there is excessive component
wear or damage.”
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» Air supply for the air springs
typically comes from the
same system that supplies
air to the air brakes.
Photo courtesy of Stemco
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