Snowmobile Polaris 2006 - 2007 FS / FST. Manual - part 53

10.13

Rear Suspension

10

Rev. 1 07/2006

IQ Switchback Front / Rear Torque Arms

Assembly Notes

• Never re-use Nylock nuts. Always replace with new 

parts.

• All pivots must rotate freely after tightening fasteners.

• Apply Polaris Premium All Season Grease to all grease 

zerks as outlined in the periodic maintenance table.

FRONT TORQUE ARM

SHOCK ASSEMBLY

LIMITER STRAPS

UPPER SHAFT

SHOCK ASSEMBLY

SHOCK ROD

REAR TORQUE ARM

REAR PIVOT (SCISSOR)

SHAFT

ADJUSTER

SLEEVE

SPRING

CARRIER WHEEL

SPACER / SET SCREW

LOWER SHAFT

SHAFT

A

B

B

B

D

D

E

B

C

C

= T 

A = 12 Ft.Lb. (16 Nm)
B = 19 Ft.Lb. (26 Nm)

C = 45 Ft.Lb. (61 Nm)
D = 35 Ft.Lb. (47 Nm)

E = 25 Ft.Lb. (34 Nm)

CAUTION

The fasteners securing the rear suspension to the 

tunnel are pre-coated with a locking agent when new. 

Never re-use these fasteners when removed. Always 

use new pre-coated fasteners when mounting the 

suspension to the tunnel.

10.14

Rear Suspension

Rev. 1 07/2006

REAR SUSPENSION OPERATION

Operation

The primary function of the rear suspension is to provide a
comfortable ride in all types of riding conditions. It separates the
rider from the ground, while allowing for complete vehicle
control. The rear suspension also must provide weight transfer
and maintain track tension.

Rear suspensions have many adjustable features for fine tuning
to achieve optimum comfort. The suspension can be adjusted to
suit rider preference and deliver excellent performance for a
given set of conditions. However, suspension adjustments
involve compromises or trade offs. A rear suspension set up to
perform well in moguls would not suit the preference of a
groomed trail rider.

Weight Transfer

The shifting of weight from the skis to the track is called weight
transfer. As engine torque is applied to the drive axle, the torque
is transferred to the track, pulling it forward. This energy also
tries to pull the suspension forward. The front torque arm reacts
to this force by pushing down on the front of the track, in effect
applying more weight to the front of the track and reducing the
weight on the skis. It is important to note that energy used to lift
the front of the machine is not available to push the vehicle
forward.

Changing the angle of the front torque arm changes the
suspension's reaction to the force. Adjusting the length of the
limiter strap will change the front torque arm angle. Shortening
the strap limits the extension of the front of the suspension;
reducing the angle of the torque arm and increasing ski pressure
during acceleration. Lengthening the strap allows the front of
the suspension to extend further; increasing the angle of the
torque arm and decreasing ski pressure during acceleration.
Limiter strap adjustment has a great affect on weight transfer.
Limiter straps only affect acceleration. It is important to check
track tension whenever limiter strap length is changed. 

Front track shock spring preload also affects weight transfer. A
stiffer spring and/or more preload on the spring transfers more
weight to the track. A softer spring and/or less preload keeps
more weight on the skis. Keep your riding application in mind
when choosing springs and setting spring preload. Soft springs/
preload will increase ski pressure, but may bottom out. Stiff
springs/preload will provide more track pressure (reduced ski
pressure), but may result in a less comfortable ride

During acceleration, the rear of the suspension will compress
and the IFS will extend, pivoting the machine about the front
torque arm. Because of this pivoting effect, rear spring and
spring preload also have some effect on weight transfer. Softer
rear springs, or less preload, allow more weight transfer to the

track and reduce ski pressure. Stiffer rear springs, or increased
preload, allow less weight transfer to the track and increase ski
pressure. The main function of the rear torque arm is to support
the weight of the vehicle and rider, as well as to provide enough
travel to absorb bumps and jumps.

Shock valving also has an effect on weight transfer. Refer to
shock tuning information in this chapter. Scissor stops also
affect weight transfer. See scissor stop information also in this
chapter.

Coupling

On all Polaris snowmobile rear suspensions, there are two
torque arms that control the movement of the rail beam. Prior to
the advent of suspension coupling, these torque arms could
move independently of each other. Rear suspension coupling
links the movement of the front and rear torque arms to each
other.

The front rear scissor stop (FRSS) couples the movement of the
front torque arm with the rear torque arm and limits the amount
of independence between the movement of the front torque arm
and the rear torque arm.

When hitting a bump, the front torque arm starts to compress.
The FRSS links that movement to the rear torque arm, causing
it to compress and raise the rear suspension up as one, allowing
the suspension to hit the bump only once and eliminating
kickback. The factory setting are usually adequate for all riders
in all conditions.

The rear-rear scissor stop (RRSS) couples the movement of the
rear torque arm with the front torque arm and limits the amount
of independent movement between the rear torque arm and the
front torque arm.

Adjusting the RRSS to a lower setting allows more weight to
transfer to the rear for more traction.

Adjusting the RRSS to a higher position will reduce weight
transfer, improve chatter bump ride and improve cornering
performance.

Torsion Spring Adjustment

Torsion spring adjustments are made by rotating the eccentric
spring block. The block provides three spring tension positions.

Torsion springs are much like coil springs, although shaped
differently. The rate of the torsion spring is controlled by the
wire diameter of the spring, and the number of coils. Pre-load is
controlled by the free opening angle. 

10.15

Rear Suspension

10

Rev. 1 07/2006

REAR SUSPENSION ADJUSTMENTS 
AND SETTINGS

Adjustment Procedures

NOTE: Break-in the suspension for at least 150
miles (240 km) before making adjustments.

All settings will vary from rider to rider, and are dependant on
rider weight, vehicle speed, riding style, and trail conditions.
Always start with the factory settings. Make individual
adjustments to suit rider preference. The machine should be
methodically tested under the same conditions after each
adjustment (trail and snow conditions, vehicle speed, riding
position, etc.) until a satisfactory ride is achieved. Adjustments
should be made to one area at a time, in order to properly
evaluate the change.

Rear Suspension Ride Height

1.

To set up the rear suspension torsion spring preload,
measure the distance between the ground and rear bumper
with out the rider on the seat and the suspension at full
extension. This can be achieved by lifting the rear of the
machine so that the suspension is off the ground and
carefully setting the machine down. Write this down as
measurement “X”.

2.

Have the rider in full gear drop down on the seat, work the
suspension slightly by bouncing up and down and sit in the
seated riding position. With the rider in the seated position
measure from the ground to the bumper in the same spot as
you did for measurement “X” and write it down as
measurement “Y”.

3.

To determine the correct ride height, subtract measurement
X from measurement Y. (X - Y = ride height).

4.

The ideal ride height is:

• IQ 121 = 4-5”(10-13cm)

• IQ RMK / Switchback = 5” (13cm)

• IQ M-10 = 3-4” (8-10cm)

5.

Adjust for the desired ride height by rotating the torsion
spring cams located on the rear of the torsion spring. 

If the rear suspension ride height cannot be adjusted to the
correct dimension, optional torsion springs may be required.
This is only an initial setup, and final spring preload may vary
based on rider preference and riding conditions.

Scissor Stop Adjustment

The front rear scissor stop (FRSS) controls the bump attitude of
the rear suspension. As the front torque arm (FTA) hits the
bump, it forces the rear scissor to collapse a predetermined
amount, depending on the FRSS block position.

This accomplishes two important things. First, it allows a lighter
spring rate on the FTA because it can borrow spring rate from the

X

Y

ROTATE

10.16

Rear Suspension

Rev. 1 07/2006

rear torsion springs. Second, it prepares the rear portion of the
suspension for the bump, reducing secondary kick back.

The FRSS is made of a resilient material allowing smooth action
and preventing any suspension component damage.

The RRSS controls weight transfer from the rear suspension to
the skis. It also influences the stiffness of the ride by controlling
the amount of coupling action between the front and rear torque
arms. To decrease weight transfer, the RRSS should be set in the
high position.

The RRSS can be removed for maximum weight transfer.
However, unless the torsion springs and rear shock valving are
changed, the ride will be compromised. Always maintain equal
adjustment on both sides.

The dot is an indicator of the HIGH position. The sides are the
LOW position and the bottom is the MEDIUM position. 

Limiter Strap Adjustment

One method of changing ski-to-snow pressure is to change the
length of the front limiter straps.

• Lengthening the straps decreases ski pressure under 

acceleration.

• Shortening the straps increases ski pressure under 

acceleration.

Set up Recommendations for Optimum Performance
(RMK / Switchback Rear Suspensions)

• DEEP POWDER SNOW: Limiter strap in LOW 

position for maximum lift and flotation

• POWDER-HARDPACK: Limiter strap in STANDARD 

position for overall handling and speed over snow.

• HARDPACK: Limiter strap in HIGH position for 

increased control and less transfer.

Torsion Spring Adjustment

To adjust the rear torsion spring, rotate the adjuster cam to the
desired adjustment. The cam has three sides, LOW, MEDIUM
and HIGH. 

HIGH

LOW

LOW

MEDIUM

Cam in LOW Position