Snowmobile Chassis Set-Up

What follows is a chassis set-up that Kevin Metheny of Ultimate Sports (USI) shares with his customers when they install a set of his X2 or SPX composite skis. This is a proven formula for those looking to maximize the installation of their high performance composite skis. When you have a stock sled and install a set of aftermarket skis, the steering behavior will change and thus the calibration can be optimized to take advantage of the newly installed handling capability.

There are many different snowmobile chassis out there and some require no adjustments at all and others require a great deal of chassis adjustment to work properly with a set of new high performance skis. Properly calibrated, it is possible to get excellent handling response with light steering effort.

The instructions below may be altered to suit your individual riding style. Some like a sports car feel where others want a smooth luxury ride. My best suggestion is to first ride your sled bone-stock for a short distance to establish a baseline and make changes as needed after that. You will know if your chassis needs to be adjusted. Always test ride your sled at least a couple of hours before you go on a long trip to get the perfect set up.

Follow these simple instructions and you will have the best handling sled you have ever owned:

1. Let your front skid frame chassis limiter straps out. Usually this will be one or two positions from stock. In some cases, all the way out is best. If they are screw type adjusters, usually 3/4” to 1.5” works great.

2. Tighten your center skid frame shock spring. If it is a cam adjuster style take it to its medium highest or highest setting. If it is a screw type, put about a 1/2 inch or more preload on the shock from stock. If it still seems heavy put another 1/4 to 1/2 an inch of preload on the shock. (You can adjust preload on any shock spring 1” inch before you need a new heavier rated spring.) If you weigh more than 250 pounds, I would go to the next heavier spring automatically. This procedure will lighten the front end considerably.

3. Tighten your front ski shock springs as well. If they are cam adjusters, adjust them to medium hard (or harder). If they are screw types put another 1/4 to 1/2 an inch of preload on them. If you have air shocks, set your shock pressure at 65-75 lbs. or even a little heavier as needed. This will stop chassis roll in the corners and give you a lighter steering feel. Add more preload if the inside ski still picks up in the corners. I know it says in your owner’s manual that loosening preload lightens the front end, but in truth it does not. Only statically does it take weight off, but while riding the opposite is true. Your sled won’t wallow in the corners as much due to too much chassis roll. Like a race car – you wouldn’t drive into a corner at high speed on shocks that were set way too soft.

4. Soften your skid frame rear end. This is where we want the weight to be carried, and this will lighten up the steering yet maintain precision handling. Guys forget to do this and if it is set to stiff you chassis won’t work and it will make steering much more difficult. No matter how much preload you put in from step 2, if you don’t soften the rear springs it will not allow the chassis to work properly and actually defeat what you were trying to gain.

Your rear suspension should bottom out (lightly) a couple (2-3 times) a day under normal riding conditions. If it does not your suspension is not working to its best potential. Tip: If your skis come off the ground 2-4 in. under full acceleration from a dead stop your chassis is working perfectly.

5. Last and possibly the most overlooked setting is “ski alignment”. Make sure this is done last and check it every time you make a chassis adjustment to your sled. I usually set mine at 1/4 to 3/8 inch tow out for trail riding. On sleds with longer wear bars this can be as easy as measuring the difference between the studs at the front of the wear bar and the studs at the rear of the wear bar.

For shorter wear bars that seem to be the norm lately we will use two of the “U” channel rails for movable shelving on walls. They are almost a perfect fit for most wear bars at 1/2” wide on the inside, and the 4’ foot length is perfect. These can be also used on smaller diameter wear bars, you have to make sure the U channels is flat against the wear bar on one side or the other.

Make sure the handlebars are centered and the skis are pointed straight ahead, then slide the U-channel under each of the wear bars. Line up the rear end of the U-channel with the rear of the ski, letting the rest of the U-channel stick out the front. Simple and straight forward, this makes your wear bars 4’ feet long and very accurate when adjusting for tow out.

Measure across the channels in the back and across the front of the skis, making the front 1/4” to 3/8” wider than the front. You should put a light bungee cord across the ski hoops when you do this adjustment to take any free play out of the bushings and guarantee you have the proper tow out on your ski alignment. The key here is we want to avoid tow-in at any time.

After these changes are made, I recommend further improving upon your set-up by making slight adjustments to only one area at a time. That way you will know if you are going in the right direction!

Follow these instructions to the letter and I guarantee you will have the best riding sled you have ever owned. I have been in this business since 1988 and an avid snowmobile rider since 1968. These settings work without fail, and the best part is you did it all on your own. Happy Riding!

By Kevin W. Metheny – USI – Ultimate Sports Inc.
Ultimate Sports Skis
765-423-2984 www.ultimatesportsskis.com

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