Adjusting Ride Height; Lowering The Front Suspension - BOMBARDIER 1996 Ski-doo MX Z440 Handbook

Bombardier has spent many hours in the wind tunnel on the hood design, and has optimized the
shape to fit the function. You cannot improve the shape of your snowmobile but you can reduce
the frontal area of the snowmobile by lowering the ride height and by using the lowest windshield
available.
The high windshield offers the rider good wind protection. That protection, however, translates
into increased frontal area and more aerodynamic drag. If you are running at a local radar run with
the high windshield on, you should sit upright behind the windshield. Crouching behind the
windshield increases drag because of interruption of the air flow from the top of the windshield to
the rider's back.
When the low windshield is fitted, the opposite is true, you should crouch behind the low
windshield for best top speeds. When crouched behind the low windshield, there is an improve-
ment in the aerodynamics compared to sitting upright behind the high windshield. That translates
into an increase in top speed of 8 km / h (5 MPH) on a Formula Mach 1 in a laboratory setting.
Because of the purity of the air flow in the wind tunnel, you should not expect this increase in
normal running, but you can always expect a 3.2 -4.8 km / h (2-3 MPH) improvement and even
more when winds are still.
Lowering the vehicle a couple of inches can also improve top speed by 1-3 MPH.

ADJUSTING RIDE HEIGHT

A cross-country racer will want all the suspension travel you can come up with for a rough and
tumble, snowcross-type event. But when racing a high speed event on a relatively smooth lake,
giving up some of the suspension travel to lower the machine is advantageous. Lowering the
machine, reducing the ride height, does 3 things for you :
1) lowers the center of gravity of the machine ; which improves cornering.
2) reduces the frontal area of the sled ; which improves aerodynamics.
3) reduces the approach angle of the track; which reduces drag.
A person wanting to lower the machine for a short event like a radar run may simply chain or strap
the machine down. Provided the course is quite smooth, this can work, but realize that strapping
down the suspension preloads the springs highly and the ride will be very stiff. This technique is
not recommended for most forms of racing.
The most common technique for lowering the machine is to use shorter springs or to shorten the
existing springs by heating and collapsing a coil or 2 of the spring as needed. Realize that
shortened springs will have very little preload when the suspension is in its "topped out" position,
and it may be necessary to safety wire the spring collars into position, and use additional limiter
devices like straps, chains or on HPG T/A shocks, a spacer can be added internally to limit the
extension of the shock.
NOTE : Some race organizations do not allow shortening springs so a proper optional
o
short spring would be used.
ADJUSTING RIDE HEIGHT

Lowering the Front Suspension

Option 1 Make limiter straps from standard rubber limiter strap material or Iinkchain and go from
shock bolt to shock bolt (longer shock bolts will be required). The length of the strap
should be adjusted to obtain the desired ride height. Most rules require you to maintain
2 inches of suspension travel. This equates to a shock eye center to center distance of
about 11.5 inches on the DSA (F-2000 & S-2000) chassis.
Section 03
CHASSIS PREPARATION
03-69