adjust snowmobile suspension
Finding the Balance
Many riders suffer through or endure poor riding snowmobiles even when they don't have to. They think that it is just a poorly made sled. This may be true of some snowmobiles, but for the most part, it is because their snowmobile suspension is not set up properly for them. Their suspension is either not providing enough weight transfer or is providing too much. Adjusting the ride height of the snowmobile's suspension to provide the best weight transfer can make your sled ride like it is on rails.
Snowmobile manufacturers try to set up their snowmobile suspensions to work well for the average rider, but they just don't have the resources to set them up for each individual rider. The problem with that is many riders do not fall into the category of the "average" rider. This is the very reason that since the mid-1990's almost all snowmobile suspensions were made to be adjustable. You have the ability to tweak different components of the suspension to make it perform differently. The key to a well riding snowmobile is finding the balance of weight transfer that is right for you as a rider.
In order to adjust the ride height of sled, you should first have a basic understanding of all the suspension components and what their function is. Once you know what each component does, you can make the adjustments to each component make your snowmobile suspension react the way that you want it to. Below is a list of the moving components that can be found on most snowmobile suspensions since the 90's.
Independent front suspensions, whether it's a-arm or trailing arm based, have front/ski shocks control the travel and dampening of the front suspension. Most ski shocks have a coil over spring that can be adjusted by turning the retaining collar. The tighter the spring is set, the stiffer the suspension will be and vice versa for a loose set shock spring. The stiffness of the spring will also affect the amount of ski pressure. More stiffness will reduce the amount of ski pressure, while decreased stiffness will provide more ski pressure.
The moveable rear arm is what connects the rear of the skid frame to the snowmobile tunnel. The rear shock is attached to the rear arm to control its movement and damping ability. The rear shock is not adjustable, but a rear shock that has failed will cause the snowmobile to be too "soft" and will bottom out in the rear with ease.
One way to adjust the weight transfer from the rear to the front is by adjusting the torsion springs. Torsion springs are attached to rear arm and are set to the suspension skid. They also help to distribute weight throughout the sled. The long arms of the torsion springs can be placed in different settings. These settings have different heights with the shortest providing the softest ride and most sag and the tallest providing the stiffest ride and least amount of sag. A heavier rider may require heavier springs to be installed.
Most modern snowmobile suspensions have coupler or stop blocks that can be adjusted behind the rear arm. Stop blocks control the amount of weight transfer by stopping the movement of the coupling system. The blocks have different length sides that control the length of movement of the arms. The shortest side of the block will provide the softest ride and the longest side of the block provides the stiffest. The amount of weight transfer allowed by the blocks can also affect your snowmobile's steering and overall handling.
Connected to the front torque arm of the suspension skid is the center shock. The front arm connects the front of the skid to the tunnel/chassis of the snowmobile and is moveable. The center shock controls the amount of movement and damping ability of the front arm. Center shocks usually have a coil over spring to help the shock rebound after being compressed. The pre-load on the shock can be adjusted by turning the retaining collar. Tighter for a stiffer ride and looser for a softer ride.
Limiter straps are attached to the front arm and the front of the skid. Their purpose is to limit how far the center shock can extend, which in turn affects the weight transfer of the snowmobile suspension and the amount of ski pressure. The tighter the strap is, the less amount of weight will be transferred. Limiter straps have a line of holes that they can be tightened or loosened to.
For the exact procedures on how to adjust these components on your particular snowmobile, consult your owner's manual.
Now that you have a basic understanding of the main moving parts of your snowmobile, you can now make adjustments to set it up perfectly. The first thing that you need to do is set your sled back to its baseline. This is where the suspension is absolutely balanced. Once you do this, you can then make minor adjustments to customize the suspension to fit you and your riding style. Follow the steps below to balance your suspension.
Shock Pre-LoadThe first thing that you will need to do is to set the pre-load of the front and center shocks. Pre-load is the measurement of the difference between the spring's free length compared to its installed length. In order to measure the pre-load, you must either lift the snowmobile off of the ground or measure with the shock uninstalled. Next, back the spring retainer off until the spring is no longer being compressed. Measure the length of the spring to get the free length of the spring. Now that you have the free length of the spring, turn the spring retainer to compress the spring to somewhere between 5-10mm. This difference will be the pre-load setting. It's important to make note of your measurements so that future adjustments can be made easier.
Limiter Straps & Coupler BlocksFor this step, the snowmobile should be sitting flat on a hard, level surface with nothing under the skis or track. Now check the limiter strap for tension. The limiter strap should be completely free of any tension. This will ensure that the weight will be distributed from the front and rear suspension. If there is extra play in the strap, you can tighten it up to remove the slack. Next, set the coupler blocks to the thinnest position facing the rear stop for a neutral setting.
Even Weight DistributionWith the previous steps done, you can now check to make sure the weight of the snowmobile is being evenly distributed from front to back. The skid of the rear suspension should be lying flat on the ground. Loosen the limiter strap if the front of rail is off of the ground. If the rear is off of the ground, you may have to adjust the preload on the front shocks to stiffen the front end.
Front Free SagThe amount the suspension compresses under its own weight is called free sag. For snowmobiles, there is no specific measurement, but a number to shoot for is to have the front free sag be about 20% of the total amount of suspension travel in the front. To check the front free sag, you will need to lift the front bumper to the point that the shocks are fully extended and then measure the height of the bumper. Next, set the sled down and compress the shocks by applying pressure to the front bumper and then release. Do this a couple of times to settle the suspension. Now measure the height of the bumper. The difference between the two measurements will be the amount of free sag in your front suspension. You can adjust the pre-load of the front shocks until you reach your desired amount of front free sag.
Rear Free SagCheck the free sag of the rear suspension by lifting the back off of the ground by the bumper and then setting it back down. When set back down, the suspension should sag a bit. If it does not, then the shocks are at full extension. You can reduce the amount of pre-load on the center shock to give the rear suspension more free sag.
Loaded/Race SagYou may need an extra set of eyes to check the loaded/race sag. Loaded/race sag is the amount of sag the suspension experiences when it has a normal riding load on it i.e. rider, luggage and gear. With the normal load on the snowmobile, the coupler blocks should be centered between the stops. If it is not, you will have to adjust the torsion springs to another setting.
Now that you have gone through these steps, you have now established a good baseline for your snowmobile suspension. The ride height and weight transfer should be well balanced. The next step is to ride the snowmobile to test it out. Because every rider is different, you may have to make further adjustments to the suspension to achieve the results that you desire. Below are some of the common problems and what you should adjust to remedy them.
Inside Ski Lifts in Corners
Your snowmobile's front ride height may be set too high. To fix this, try reducing the amount of pre-load on the front shock springs. This will help to lower the center of gravity to make the snowmobile less tippy in corners.
Diving In Corners/Body Roll
This is the opposite of the inside ski lift. While cornering, the momentum of the snowmobile with over compress the inside front shock. To fix this, try adding more pre-load to the front shocks to stiffen them.
Ski Lift While Throttling Out of a Corner
If the ride height is set to be balanced from front to rear, you can adjust the coupler blocks so that the system stops sooner during the transfer. More load will be left on the skis to keep them down as you apply the throttle.
Rear End Drops and Raises with Ease
The most common cause of this is the ride height being out of balance. If you have the ride height set properly, then you can rule out other possible problems. It could be that a shock is blown or the torsion spring is broken. These problems are very rare though and should only be considered after the ride height settings have been reevaluated.
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