Shock Absorber; Hpg (High Pressure Gas) - BOMBARDIER 1996 Ski-doo MX Z440 Handbook

SHOCK ABSORBER

INTRODUCTION
A shock absorber could more accurately be called a damper as its main function is to control or
dampen suspension oscillations. Without shocks, a suspension system would bounce for quite a
while after hitting a bump and the vehicle would not offer as good a ride or control. A shock works
by moving a valved piston through a chamber of oil. The less resistance to oil flow through the
piston, the less dampening the shock provides. Conversely, more resistance to oil flow equals
more dampening. Bombardier uses a variety of shock absorber types which vary on the exact
application and requirements for performance.
As dampers of the air/ oil type are cycled rapidly, a low pressure will be generated on the oil exit
side of the valved piston. If the pressure drops too much, a vaporization or aeration of the oil can
occur. If this oil aeration is allowed to continue, a loss in damping performance will result. This is
called shock "fading". This condition can be compensated for if the engineers know the exact
application and performance requirements of the damper.
A06FOMS
Oil
2. Aeration
3. Low pressure
This aeration can be eliminated by pressurizing the oil. HPG shocks use a floating piston design
(except some center shocks). This design allows an oil chamber and a gas chamber in the same
single damper body.
The gas chamber of the shock absorber is filled with nitrogen gas at 300 PSI (2070 kPa). This
pressurizes the oil reservoir portion of the shock which prevents the oil from aerating. The gas
pressure should not be changed as a way of tuning the shock. Calibration should be done with the
piston and valve shims.
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