Rear Suspension Adjustments

Content Source: 2021 550 Indy 144 Owner’s Manual (9931273 R01) > The Perfect Fit Chapter

IMPORTANT

The Owner's Manual for this vehicle contains warnings, instructions and other information you must read and fully understand before safely riding or performing maintenance on this vehicle.Always follow the warnings and instructions in Owner's Manual.

Click the CONTENTS link above for the Table Of Contents, or download a full PDF of the Owner Manual in the Owner Support area of Polaris.com

Rear Suspension Adjustments

Rider weight, riding style, trail conditions, and vehicle speed all affect suspension action.

Each rear suspension can be adjusted to suit rider preference and deliver excellent performance for a given set of conditions. However, all suspension designs and adjustments involve a compromise, or trade-off. For example, a suspension set up for snowcross racing would provide a very stiff ride on the trail. A suspension set up for trail riding would bottom out harshly on a snowcross course.

Refer to the suspension setup label on your snowmobile, or your POLARIS dealer can provide the initial suspension setup information. Additional adjustments can be made after initial setup. Make adjustments to one area at a time so you can evaluate the change. For further assistance, your dealer can assist.

Suspension Performance Tips

Rider weight usually determines the position at which the spring preload should be set. However, this may vary with riding style. With a little experimentation, each rider can find a preferred set-up. These adjustments are easy to make, involve very little time or effort, and greatly affect the ride.
In deep snow, a new rail slide will offer improved performance over a worn rail slide. It can also improve top speed.
When riding on ice or hard-packed snow, adding a set of bogie wheels to the rail may enhance the snowmobile’s performance. Bogie wheel kits are available from your dealer.
POLARIS offers track kits for improved flotation in deep snow. See your dealer for assistance.

TIP

Keep the suspension pivot points lubricated. This will reduce moisture and rust build-up and ensure proper function of the suspension components. Grease rear suspension pivots before adjusting the rear suspension.

Track Tension

Track adjustment is critical for proper handling. Always maintain correct tension and alignment. Refer to the track tension maintenance section of this manual.

Rear Track Shock Spring (144)

Measure the rear track shock spring length and adjust to the appropriate length based on rider weight. Include passenger weight (if applicable) and all riding gear, accessories and cargo weight in the calculation.

WARNING

Allow a passenger to ride only on models equipped with a passenger seat.

Securely elevate and support the rear of the snowmobile to remove the weight from the suspension.
Use a tape measure to measure the spring installed length between the two spring retainers.
Refer to the chart on the next page to determine the correct spring length for rider weight. If adjustment is needed, clear away any snow or ice trapped within the spring or threads.
Using a spanner wrench, rotate the spring to adjust length.

NOTICE

Never adjust a spring beyond the maximum adjustment length shown in the chart. Adjusting beyond maximum adjustment will cause the spring to bottom and result in damage to your rear suspension.

Adjust the rear track shock spring per the charts on below.

EVO RMK Models

REAR TRACK SHOCK SPRING (RTSS) SET-UP (Standard Spring) Measure spring length with suspension off the ground
Rider Weight(including all riders, gear, cargo, & accessories		Model	Installed Spring Length(rear suspension off the ground)
Shaded cells indicate factory settings.
< 160 lbs	< 73 kg	EVO RMK	9.5 in.	24.1 cm

160-220 lbs	73-100 kg	EVO RMK	9.12 in.	23.2 cm

220-280 lbs.	100-127 kg	EVO RMK	8.75 in.	22.2 cm
*RMK EVO maximum adjustment is 8.5 in. (21.6 cm)

550 INDY Models

REAR TRACK SHOCK SPRING (RTSS) SET-UP (Standard Spring) Measure spring length with suspension off the ground
Rider Weight (including all riders, gear, cargo, & accessories		Model	Installed Spring Length (rear suspension off the ground)
Shaded cells indicate factory settings.
< 160 lbs	< 73 kg	550 INDY Adventure/Voyageur/LXT	11.125"	28.2 cm
		550 INDY 144
160-220 lbs	73-100 kg	550 INDY Adventure/Voyageur/LXT	10.75"	27.3 cm
		550 INDY 144	10.5"	26.7 cm
220-280 lbs.	100-127 kg	550 INDY Adventure/Voyageur/LXT	10.5"	26.7 cm
		550 INDY 144	10.125"	25.7 cm
280-340 lbs.	127-154 kg	550 INDY Adventure/Voyageur/LXT	10.125"	25.7 cm
		550 INDY 144	9.75" Maximum Adjustment	24.7 cm Maximum Adjustment
340-360 lbs.	154-163 kg	550 INDY Adventure/Voyageur/LXT	9.875" Maximum Adjustment	25 cm Maximum Adjustment

Initial Spring Preload Setting (Sag Method)

To set up the rear suspension torsion spring preload, measure the distance between the ground and rear bumper. This is measurement X.

Take the first measurement with no rider and with the rear suspension at full extension.

TIP

The rear bumper may need to be lifted upward slightly to fully extend the suspension.

Next, have the rider drop down hard on the seat and bounce up and down several times, collapsing the rear suspension. With the rider seated, measure the distance between the ground and the rear bumper at the exact location used for measurement X. This is measurement Y.

To determine sag, commonly referred to as ride-in, subtract measurement Y from X (sag=X-Y). If the measured sag is incorrect, adjust the FRA position and/or rear torsion spring preload.

Suspension	Recommended Sag	Adjustment	See Page
INDY 121	3-4 inches (7.5-10 cm)	Torsion Spring Preload	Torsion Spring Preload (121)
INDY 155	4 inches (10 cm)	Torsion Spring Preload	Torsion Spring Preload (155)
INDY EVO	1.5-2.5 inches (3.8-6.3 cm)	Torsion Spring Preload	Torsion Spring Preload (121)

TIP

This is only an initial setup, and final spring preload may vary based on rider preference and riding conditions. Accessory springs with a higher load rating are available for some models. Please see your dealer for availability.

Torsion Spring Preload (121)

To adjust rear torsion spring preload, rotate the three-position cam using the engine spark plug tool. Adjustment is easiest when the cam is rotated from low to medium, and then to high. Rotating directly from low to high will require significantly more effort.

Different rate torsion springs are available if a firmer ride is desired. See your dealer for more information.


Low	Medium	High

Torsion Spring Preload (155)

To adjust rear torsion spring preload, rotate the three-position cam using the engine spark plug tool. Different rate torsion springs are available if a firmer ride is desired. See your dealer for more information.

The following information is provided only as a guideline to be used for initial suspension set-up. Your set-up may vary based on your desired riding style.


Soft (long end of cam to front)	Medium (short end of cam up)	Firm (long end of cam up)

Limiter Strap Position (Ski Pressure)

Ski pressure is set at the factory to deliver the optimum balance between ride and handling. If a rider prefers more ski pressure for improved steering performance, adjustments can be made to the front limiter strap

. Tighten the strap to increase ski pressure. Loosen the strap to reduce ski pressure.

Remove the nuts and flat washers from the upper limiter strap.
Relocate the strap to the desired position.
Reinstall the nuts and washers. Tighten securely.

Suspension Coupling (121 Models Only)

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.

There are two types of rear suspension coupling.

Front To Rear Coupling and the Front Rear Scissor Stop (FRSS)

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 the 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 reducing kickback.

The factory setting is usually adequate for all riders and conditions.

Rear To Front Coupling and the Rear Rear Scissor Stop (RRSS)

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 and the front torque arm.

Adjusting the RRSS either allows more weight to transfer to the rear for more traction, or allows less weight to transfer to the rear, resulting in improved cornering performance. An adjustment dot is located on the RRSS. This dot is on the longest end of the scissor stop.

Rear Rear Scissor Stop (RRSS) - Attributes

Moving the RRSS to a higher position will have the following effects on the suspension:

Reduced weight transfer
Improved chatter bump ride
Improved cornering performance
Increased load carrying capacity (2–up)

Weight Transfer During Acceleration

The preferred method for controlling weight transfer during acceleration is by adjusting the rear rear scissor stop (RRSS). The factory setting is the best for most trail riding conditions.

To decrease weight transfer under acceleration (for improved cornering), rotate the RRSS to a higher position.

To increase weight transfer or ski lift during acceleration, rotate the RRSS to a lower position.

NOTICE

When adjusting for weight transfer, both the left and right rear rear scissor stop adjuster blocks must be adjusted to the same position.

High

Medium

Low

TIP

Your dealer can help you with initial setup and additional setup instructions to help you achieve your optimum ride. A scissor stop tool is also available from your dealer.