How To's  

Setting Snowmobile Ride Height

10/15/2012

Why Set Up Your Suspension?

The importance of setting up the suspension of your snowmobile cannot be stressed enough.  It can make all the difference between a good day or a bad day of riding.  Nearly all suspensions offer some type of adjustability.  The most common adjustment that they all have is ride height.  Setting ride height is the first step towards establishing a baseline for any vehicle.  Once a baseline is established and the vehicle is ridden, further adjustments can be made to better suit rider preference.  Modifications to the suspension such as valving, springs, reservoirs, etc, can be made if the adjustments available don’t give you the level of performance you’re looking for.

 

Understanding Snowmobile Suspension

The front suspension (a-arms) and rear suspension (skid) are connected via a rigid chassis.  Changes made to the front suspension will affect the rear, and vice versa. You can test this theory by pressing down on your front bumper.  You will notice that doing so causes the rear of the vehicle to rise up.  Conversely pulling up on your front bumper causes the rear end to lower itself down.  The best handling vehicle is one that is balanced and level front to rear. 

 

Setting your ride height

The steps outlined below will apply to the majority of snowmobiles manufactured since the mid 90’s.  Some features and specifics may differ slightly, but the overall theory remains the same.  Performing the following tasks will give you the best balance and ride possible from your stock or modified suspension. 

1.)    First things first:  Maintenance

The riding season is never long enough.  Preventative maintenance and pre-season checks go a long way towards reducing the chances of having a problem in the middle of winter.  Check for bent or broken suspension components.  Check bushings and pivot points for excessive play and grease as needed.  A suspension with seized or worn pivot points will not perform well.  Annual shock service is good practice for preventative maintenance.  This is particularly true for small capacity, non-reservoir shocks, and riders that ride 1,000 miles or more per year. While it is difficult to know the internal condition of shocks without disassembling them or running them on a dyno, it is possible to give them a quick evaluation in the comfort of your own garage.

Pull the shocks out of the vehicle and remove the springs.  Compress the shock.  The action should be smooth, and the shock should rebound to full extended length on its own.  If the shock fails to fully extend, you can hear air bubbles in the shock, or if you see oil leaking out, it’s time for a rebuild. Tip:  Measure the freelength of your springs before reinstalling them on the shocks.  You’ll need this measurement in order to set your spring preload in step 2.

 

2.)     Spring preload

Preload must be measured without any load on the springs.  The vehicle must be off the ground, or the shocks should be taken out of the vehicle.  Preload is measured as the difference between a spring’s free length and its installed length.  Freelength of a spring is its length from end to end without preload or vehicle load applied.  Once you have determined the freelength of your springs, set the preload to between 5 and 10mm on both the front and center shocks.  As an example, if the freelength of your spring is 120mm, add preload until the measurement from end to end is between 110mm and 115mm.

 

 

3.)     Check your limiter strap and coupling system

Place the snowmobile on a hard, level surface.  Do not place anything such as dolly wheels or blocks under the skis or track.  Adjust the length of the limiter strap, making sure it does not have any tension on it.  If your sled has a rear suspension coupling adjuster it should be set with the thinnest side of the adjuster block is facing the rear stop.  Coupling systems vary by model and year.  Check your owner’s manual and become familiar with the system on your vehicle.

 

4.)     Check weight distribution

After performing steps two and three take a look at the vehicle.  Are the skid rails resting level on the ground?  If the front of the rails are off the ground, chances are the limiter strap needs to be loosened.  If the rear of the rails are up, try increasing the front shock preload, this will transfer more weight to the rear. 

 

5.)    Check front free sag

Free sag is the measure of how much the suspension in a vehicle compresses under its own weight, without a rider.  Unlike motocross bikes, there is no specific free sag number; every snowmobile is a little different due to chassis design.  General rule of thumb is to set front sag at around 20% of the total front travel.  If for instance your front skis have 10 inches of travel, you will want around 2 inches of free sag.  Free sag can be measured at the front bumper.  To check your front free sag, first lift up on the front bumper until the shocks are fully extended.  Make note of the bumper height.  Set the sled down and bounce down on the bumper a few times to settle the suspension.  Measure the bumper height again.  The difference between this measurement and the one taken at full extension is your free sag.  Increase or decrease front spring preload as needed to adjust the amount of free sag.

 

6.)    Check rear free sag

Lift the rear of the vehicle up off the ground and then set it back down.  The suspension should sag in under its own weight.  Again, there is no “magic” number to look for.  The friction between the rails and the track make it very difficult to get a consistent measurement.  The most important thing when checking rear free sag is to make sure you have some sag and are not topping out.  When you lift up on the rear bumper the sled should not quickly slam into full extension.  If this does occur, try reducing the preload on the center shock.

 

7.)    Set Race sag

Race sag, also known as loaded sag, is the amount the suspension is displaced by rider, gear, luggage, etc.  As mentioned before, the design of a snowmobile suspension makes it very difficult to get consistent measurements at the bumper.  Instead, use the coupling system as a guide.  With rider positioned on the sled, along with gear and any additional load typically carried check that the coupler device is centered in the stops.  The coupler blocks should not be resting on the rear stops when the rider and load are on the vehicle.  Adjusting the torsion spring settings will change where the coupler device rests.  You will notice that the front sag has minimal change, if any with or without a rider.  This is normal on a modern snowmobile.

 

8.)     Get out and ride

Take a test ride and see how the vehicle handles.  It may take more than one test ride to accurately evaluate the suspension.  If handling problems persist refer to the trouble shooting guide.

 

Suspension Troubleshooting Guide

Handling problems are often caused by an imbalanced chassis.  Here are a couple common scenarios, and possible solutions:

 

Problem:  Excessive body roll or diving in corners

Possible solution:Try adding preload to the front springs.  Some snowmobiles come with progressively wound springs, and it may be difficult to add preload without affecting the overall ride quality of the vehicle.  Installing a dual rate spring kit calibrated for the rider’s weight will provide an initial spring rate sufficient to combat body roll, while at the same time maintaining a good ride.

 

Problem:  Vehicle tips up when cornering, lifting the inside ski 

Possible solution:Most roll or ski tip situations are generally related to excessive spring preload.  Try removing preload from the front springs.  This will lower the front ride height and center of gravity, improving handling. 

 

Problem: Heavy steering

Possible solution: Unless you have switched to an aggressive ski and/or carbide, heavy steering can often be traced back to the rear suspension.  Check the center shock preload, torsion spring settings, and coupling system.  Center shock spring preload should be between 5 and 10mm.  Adjust the coupling system so that transfer occurs later in the suspension travel. This will allow more weight transfer to the rear, and off of the skis.

 

Problem: Skis come off the ground when trying to accelerate out of a corner

Possible solution:Check ride height and balance front to rear.  Adjust the coupler system such that coupling occurs earlier.  This will reduce weight transfer and keep the load on the skis.

 

Problem:Rear bumper is topped out when the vehicle is at rest

Possible solution:This often is from excessive torsion spring preload as a rider tries to compensate for bottoming resistance. Springs should be used to set ride height; adjust shock valving to achieve bottoming resistance.

 

Problem: Rear end raises up easily and then drops with little effort        

Possible solution:One of the most common causes of excessive rear sag is a geometry-related issue such a limit strap being pulled in or a vehicle isn’t resting on a flat surface. It’s rare for a snowmobile to sag from weak torsion springs.  Another common misconception is blown shocks causing excessive sag. The reality is that a shock with a fresh charge may help a little bit, but the overall effect is negligible. Instead, check ride-height settings.

 

About Hygear Suspension

Hygear Suspension has a simple mission; Build the best suspension possible without compromise.  Hygear offers a full line of products and services to modify, repair and maintain your suspension components, no matter what you ride.  All of Hygear Suspension’s products and services are backed with industry leading customer service, including our exclusive Data Tracking System and Free Revalve Policy

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