Choosing Between Lightweight Coil & Air Sled Shocks

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Ever wonder whether coil or air is the right set up for you and your sled? FOX Backcountry Team shredder Chris Burandt walks us through some of the similarities and differences between the two. Thankfully, with the new lightweight coil and air packages from FOX, you can save significant amounts of energy no matter which package you choose. 

Saving Energy 101 

It can seem counter-intuitive at first, but the shocks should be one of the first places you look to shed weight from your sled. Why, you ask? Let’s dive in below. 

Imagine holding a 25-pound weight right next to your chest. Pretty easy, right? Exactly: your shoulders and arms could hold it here for a long time. But what happens if you take that same 25-pound weight and extend your arms straight out, parallel with the ground? Gravity will now have more leverage over the same 25-pound weight because it is further away from your shoulders. As a result, it’ll be significantly harder to hold the weight in this position. 

It’s the same effect with your ski shocks. 

It’s important to get the sled on edge while side hilling and easier to do so with less outboard weight. Burandt shows us how.

As Burandt says in the video, ski shocks are “outboard weight,” meaning they are located further away from the center of the sled, like the weight being further away from your body. 

A day of mountain riding can involve transitioning the sled from edge-to-edge hundreds of times. If gravity is pulling on a lighter shock, it makes the sled much easier for you to move. 

Any time you can decrease the amount of “outboard weight” your sled has, it’ll have a big impact on the handling characteristics of your machine and save you energy. 

Ashley Chaffin carves fresh powder. With lighter shocks, it’s easier to move from edge-to-edge.

Coil or Air? 

Thankfully both of these are good choices in our new Lightweight line. The new coil shocks save 21% weight and the new air shocks save 15% weight over our previous years’ offerings. 

If you’re looking to directly compare the two, you save a total of approximately 2 lbs. by choosing the new Lightweight air shocks over the new Lightweight coil shocks. 

Both lightweight coil and air shocks come with QS3 and QSR adjusters.

As we mentioned above, saving weight matters. But there are a few other things to consider when it comes to choosing between the two lightweight offerings: coil and air. 

Coil: Just the Right Amount of Adjustments 

Think of coil shocks as the comfortable, set-it-up-once type of option. 

You can set up the sag on these shocks once and not have to worry about them. Regardless if it’s 30 degrees at 4,000 feet of elevation or -17 degrees at 8,000 feet of elevation, because coil springs perform effectively the same at every temperature and elevation. 

Why Setting Sag On Your Snowmobile Matters”

Coil shocks have what is called a “linear” coil spring. This means that the force it takes to compress the spring increases at a constant rate as the shock compresses through its travel. This is what makes coil shocks plush but can also cause them to bottom-out easier than air shocks. 

Ride-wise, coil shocks have a comfortable and plush feel over choppy and rough trails or hard-pack, icy snow. This is in-part due to the “linear” spring mentioned above but is also because coil shocks don’t have the extra seals an air spring needs. Therefore, they have less friction and can respond smoother and easier to small changes in the snow.  

Sure, the new lightweight coil shocks smooth out rough trail. But Carl Kuster shows us that the smoothest way is still to jump.

Some coil shocks suffer from harsh bottom-outs after landing jumps or large drops during aggressive mountain riding. But the new lightweight coil shocks use FOX’s proprietary Internal Bypass spiral groove technology. This progressively ramps up damping support in the final stages of shock travel so that shock compression from large features remains comfortable and doesn’t unsettle you or your sled. 

Air: Infinite Adjustability 

Think of air shocks as the supportive, can-be-set-up-for-anything type of option. 

It’s easier to adjust the air pressure in the main and EVOL chambers using a shock pump than it is to turn the coil springs to make a preload adjustment. Air springs allow you to dial in very small adjustments to get the exact feel you’re looking for. 

But air pressure is more likely to be affected by temperature. So, if you set up sag on your sled inside your 60-degree garage, but then go ride in -5 degrees at 6,500 feet of elevation, the feel of the shocks will be different than they were at initial set up.  

We recommend checking and setting pressures and set up right before you start riding for the day that way you can do it in the most similar conditions to what you’ll actually ride in. 

Air shocks have what is called a “progressive” air spring. This means that the force it takes to compress the spring increases at an exponential rate as the shock compresses through its travel. This type of spring is what allows air shocks to resist bottoming-out better than coil shocks. 

See how the air’s spring rate “curves” up on the right-hand side at the end of the shock travel? That’s what “progressive” looks like. It is the force it takes to compress the shock “increasing at an exponential rate”. With the EVOL chamber and main chamber, you can fine tune how progressive you want the shock to be.

Ride-wise, air shocks perform their best when being ridden aggressively: long jumps, big drops, and carving corners. This is in large-part due to the progressivity of the air spring mentioned above, which provides a bottomless feel because it requires more force to bottom-out. Additionally, their lighter weight makes it easier to transition from edge-to-edge as your carving corners in powder. 

Some air shocks suffer from feeling stiff while riding over choppy or rough trails. But the new lightweight air shocks utilize FOX’s proprietary Internal Bypass spiral groove technology. This initially allows the shocks to move freely to ensure they’re plush over rough snow, which keeps you comfortable. But as you compress further into the travel, internal bypass progressively ramps up damping support in the final stages of shock travel so that shock compression from large features remains comfortable and the air shocks retain their bottomless feel.  

What’s the best for you?

So, Which One? 

Since you can get Quick Switch 3 (QS3) and rebound adjusters along with Internal Bypass spiral groove technology on both lightweight coil and lightweight air shocks, you really can’t go wrong. 

Maybe ask yourself: do you like to “set and forget” or “tinker to find the perfect setup”?  

If you just want to ride the sled, going with coil will let you do that no matter where you ride. But if you’re the type that keeps a notebook to write down settings, observations, and more, the air shocks will be right up your alley. 


Like what you see? Check out all the FOX Academy videos for powered vehicles and mountain bikes here.

Want to learn from the pros? Check out the FOX Backcountry team.