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Shock Tech

What you need to know about your snowmobile's shocks

Published online: Dec 22, 2009 Feature Ryan Harris
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Your sled's shocks can be the reason you either love or hate your snowmobile. And yet they are often the most neglected area of the machine when it comes to time spent on tuning. Trust us: all it takes is one ride on a dialed-in sled to make you realize what you're missing-even just by making adjustments to existing components.

One of the reasons that shocks are overlooked is because they are-individually and as a suspension system-complex. You can adjust, manipulate and change a sled's handling by changing springs, adjusting spring preload tension, high-speed compression damping, low-speed compression damping, rebound damping, oil levels, valving, air pressure, needle size, etc. However, there are just a few things you really need to know to gain better control of your sled's suspension. Most modern mountain sleds come equipped with high-quality shocks that offer a wide range of adjustment. And if yours doesn't, there are several options for aftermarket shocks that would change your perspective on your sled's handling.

Compression

Compression clickers are very common on sleds these days. This adjustment is made by turning the clicker screw in or out, and position is measured by counting the number of clicks out from all the way in. Compression adjustments change how the shock compresses to absorb impact from bumps, landings and terrain variations. Turning the clicker in makes the shock resist compressing, thus resulting in a stiffer feel which will be more resistant to bottoming out. Turning the clicker out lets the shock compress bumps easier, feeling softer and reaching the bottom of the shaft stroke easier.

Some shocks, like the Fox Float R Evol, have high-speed compression and low-speed compression clickers. The terminology represents the shock shaft movement, not necessarily the speed of the snowmobile. High-speed clicker adjustments will change how the shock absorbs sudden impacts, like square-edged holes, hard icy bumps, firm flat landings, etc. Turning the high-speed clicker in will increase the shock's damping to make the ride firmer and keep the sled riding higher in the bumps (by not letting the shock move as far down on the shaft). Low-speed adjustments are for rolling whoops on trails, transition landings (where the sled lands with the slope) and lifters. Most mountain terrain once off the trail will play into the low-speed adjustment.

It's important to make small adjustments and spend enough time making adjustments so that you can tell a difference. Sometimes a soft compression setting can feel stiff (because the bottom of the stroke will be reached sooner) while sometimes a stiff compression setting can feel soft (because the lack of shaft movement can feel like the shock is bottoming out). Play around with shock adjustment until you can tell a difference.

Rebound

If compression controls the rate at which the shock collapses to absorb impact, rebound is the rate at which it re-extends to ready for the next blow. If you've ever ridden a sled where the rear end feels like it's trying to kick you over the handlebars, you know what too fast rebound damping can do. If the rebound is too slow, the shock will stay collapsed from one bump to the next and you are riding on a sled with an inch of travel. How do you tell? The rear end is easier to feel than the skis. If the skid kicks the back of the sled straight up as you blitz through a rough mogul section, then the rebound is too fast. If the rear end starts swapping side to side, the rebound is too slow. On the ski shocks, if the front end seems to thud through the bumps and jar your wrists, the rebound is too slow.

Very few snowmobile shocks feature rebound clickers, but if you have ones that do, remember that turning the rebound adjuster screw in slows the rebound and turning it out speeds the rebound up.

Springs

Compression and rebound damping may control the action of the shock shaft, but the spring supports the weight of the rider and sled. This is why sag is so important. Sag is how far the shock settles under the weight of the snowmobile and rider. The formula between compression and rebound settings and valving only work if the right spring is used for the weight load. If your shocks are set up for a 160-pound rider and you weigh 225, adjusting the compression clickers won't fix your problem. You need stiffer springs. Or, if your sled has preload collars threaded onto the shock body, you can turn them to tighten or soften the preload of the shock spring. There is a fairly wide range of adjustment here, so use it. Ideally, the best thing to do is match your weight and riding style to the proper spring to begin with, but the easy fix is changing the preload adjuster.

There are steel springs (most common) and titanium springs. And there are air shocks, which use either compressed air or nitrogen to replace the coil spring, such as with the Fox Float and Walker Evans Air shocks. They are lighter thanks to not having a steel coil spring. And preload is easy to adjust by adding or decreasing air pressure with a hand pump (Fox Float) or changing the nitrogen pressure (Walker Evans Air).

Rebuild

If you've tried all of these tuning tips and just aren't getting the right performance out of your shocks that you think you should be getting or you fall outside the industry average of a 160-pound casual-aggressive rider, then you should have your shocks rebuilt by someone who knows what they're doing. Many dealerships can either rebuild the shocks in-house or pull them off the sled for you and send them to someone who can. The other option is to remove the shocks from the front end and the skid frame yourself and take or ship them somewhere. Tom's Snowmobile Service is the Factory Connection of snowmobiling. You can ship your shocks to Tom's, along with your weight and riding style and they will rebuild them and ship them back. Tom's specializes in Fox; there are other shops that specialize in Walker Evans, Kayaba (KYB), Ryde FX, Ohlins, Exit and other shock brands. You can even go with coil spring upgrades, like RCS titanium springs.

Replace

If all else fails, or if you've either worn out the OEM shocks or are looking for an upgrade in performance capabilities, you should look at buying a set of aftermarket shocks.

Many of the OE suppliers also offer high-performance shocks. Fox has its Zero Pros and Float R Evols. Walker Evans has its compression-adjustable air shocks and needle coil-overs. ARS-FX has its Exit line of race-grade coil-over shocks. Ryde FX has other shock options as well. You can even order shock upgrades through OEMs, like upgrading the shocks on your Summit to the HPG KYB shocks found on the Summit X-RS. You just need to determine what your objectives are (weight savings, hillclimbing, cornice drops) and how much you want to invest. Whatever you do, we promise you will come away with a whole new love for your snowmobile.