Air shocks continue to dominate the mountain bike market, but coil shocks have become trendy again thanks to the influence of professional enduro racing.
A number of pro enduro riders choose coil shocks for events that have long and gnarly downhill stages. Enduro World Series overall winner Tracy Mosley was one of the first top riders to adopt coil-shock technology. That's not surprising, given her experience on the World Cup downhill circuit, where a coil shock has always been the weapon of choice.
Shock technology has improved to the point where coil shocks are viable beyond the realm of pure downhill racing. Many mountain bikers have seen pros like Mosley win on coil shocks and have decided to take their bike’s downhill performance to the next level, swapping out air shocks for coils. Some enduro bike models even come stock from the factory with coil shocks. The tide is turning.
Is it time for you to put a coil shock on your trail or enduro bike? Let's take a look at the pros and cons of coil and air shocks so you can understand the differences and decide which is the better choice for your bike, terrain, and riding preferences.
- Supple feel with less stiction (resistance to movement at the beginning of the shock's travel)
- Consistent performance and resistance to heat that can build up on a long descent
- More reliable, less-frequent maintenance required (every 12 months)
- Heavier weight
- Changing the spring rate is more involved — you need to remove the spring entirely and replace it with a stiffer or softer spring
- Less bottom-out resistance on more linear suspension designs
As we mentioned at the top, enduro racing has made coils cool again. They are great for long, rough downhills, require less maintenance, and are very supple.
A wound coil spring on one of these shocks does not heat up as drastically as a pressurized air spring does on long downhills as it is repeatedly compressed. There are two key benefits to a cooler shock: The coil shock's damper does not heat up as much, so its performance stays more consistent, and the spring rate of a coil will not change during intense cycles. (More on heat fade in a moment.)
Coil shocks also require fewer seals than air shocks, resulting in less stiction — static friction created by seals against a shock shaft. The amount of force required to break this stiction is called the breakaway force. Because coils have less stiction and a lower breakaway force they have better small-bump sensitivity and a plusher, suppler feel.
This increased sensitivity can also improve traction, as it allows the rear wheel to track the ground more consistently. Bikes with coil shocks usually feel more planted in rough terrain.
Fewer seals also mean coil shocks generally require less maintenance and aren’t as affected by dirt, dust, and grime. Most coil shock manufacturers recommend a rebuild every 12 months.
However, coil shocks weigh significantly more than air shocks — about one pound. A metal spring will always weigh more than air. It is also more difficult to change the spring rate for coil shocks. You have to remove the shock and swap out the coil spring. Riders may have to buy multiple springs to dial in the correct spring rate for their bike, terrain, and weight. This can get expensive.
Another consideration is the coil's linear spring rate. This contributes to the plush and planted feel, but it also means that coil shocks have less bottom-out resistance. Some bikes are designed around an air shock and not meant to have a coil shock. The suspension design of these bikes will have a linear leverage rate that relies on an air spring's progression to provide bottom-out resistance. When combined with a coil shock, there might not be enough suspension progression to prevent harsh bottom-outs during big hits. This forces riders to run an excessively high spring rate or excessive compression damping to compensate, which can cause a bike to feel harsh or dead.
Plenty of riders successfully fit coil shocks on bikes with linear leverage rates, but coil shocks usually play best with bikes that a more progressive suspension leverage rate. Some bike manufacturers may recommend against using a coil shock due to a frame’s linear leverage rate or particular fitment issues. For example, Ibis and Pivot do not recommend coil springs on their trail or enduro models.
In general, Yeti, Trek, and older Santa Cruz models, like the 2018 Hightower, have more linear suspension. Other manufacturers, such as YT, Orbea, Specialized, and Commencal offer coil shocks as stock options on certain enduro bikes.
If you are ever unsure if a coil shock is compatible with your frame, always check with your bike’s manufacturer.
- Lighter weight, potentially 500 grams lighter compared to a coil shock
- Easy to tune spring rate by changing air pressure
- Better bottom-out resistance
- Greater stiction and breakaway force, which can lead to a harsh feel
- Performance fades or changes due to heat on long downhills
- Requires more regular service and maintenance (every six months)
In the last 10-15 years, air shocks have become the dominant choice for most production mountain bikes. Air shocks are reliable, simple, and great for the majority of applications. They rely on an air spring created by an airtight chamber in the shock. This chamber is filled using a shock pump. It is easy to change the spring rate of an air shock to suit different bikes, terrain, and rider weights. You can even do so mid-ride.
The air spring also allows riders to dial in the spring rate more accurately than coil springs. Coil springs are generally available in increments of 25-50lbs/in and there is a chance that your ideal spring weight is between two available springs. An air spring can be set to the exact PSI to provide your desired sag, ride feel, and bottom-out resistance.
The air spring is also more progressive than a coil spring. As the air is compressed through the shock's travel, it becomes harder to compress it further. This helps prevent an air shock from bottoming out and allows it to play well with suspension designs that have a more linear leverage rate. The progression and bottom-out resistance of most air shocks can be fine-tuned with volume reducers or spacers that fit inside the air chamber. This is useful for riders who are pushing the limits of their bike and need more support for bit hits and rough terrain.
Because air shocks are more progressive, they have a reputation for making bikes feel more playful and easier to jump and pop off trail features. They are also significantly lighter than coil shocks. Bigger, burlier air shocks aimed at the enduro and downhill market have also made a great deal of progress in recent years. Downhill-focused air shocks are designed with significantly larger air and oil volumes to improve fade resistance and provide a supple feel that can come close to the feel of a coil shock.
There are three key downsides to an air shock: increased stiction, heat fade, and maintenance.
An air shock needs additional seals to create an airtight chamber, which increases stiction. Even the best air shocks can’t fully match the supple feel and low breakaway force of a coil shock due to those seals.
As mentioned earlier, air shocks are prone to heating up on long downhills, even the bigger air shocks aimed at the downhill and enduro market. When the air spring is subjected to repeated compressions, the entire shock heats up. This causes the air spring to become stiffer and the damping to become less effective because the shock oil is thinner at high temperatures. The longer and rougher your downhill runs are, the more this will be a concern.
Stiction will also increase as a shock’s seals and oil degrade or become contaminated with dirt, dust, and grime. It’s often recommended that air shocks be serviced at least every six months to maintain performance — potentially more frequently if you ride a lot or ride in harsh conditions.
Which Shock is For You?
Choose a coil shock if:
- You ride in a bike park or on downhill trails and need a shock that can handle long descents without losing performance.
- You are looking for better small-bump sensitivity or traction at the rear end of your bike.
- You prefer a rear end that feels more planted and less lively.
- You don’t want to maintain or service your shock as much.
- You like to experiment and tinker and/or you think coil shocks look cool.
Choose an air shock if:
- You do more trail riding that includes plenty of uphills and flatter terrain.
- You want to keep your bike light and a coil shock will add too much extra weight.
- You prefer a rear end that feels more playful and poppy.
- You need more progression in your shock to resist bottoming out during big hits.
- You like to quickly and easily change and tune your spring rate based on conditions, terrain, or riding weight.
What Do Riders at The Pro’s Closet Think?
We polled the mountain bikers in the shop to see what our own employees prefer when it comes to coil versus air shocks. There are around 30 riders in the shop with trail or enduro bikes. Of these riders, only two are currently riding a coil shock. Everyone else is on an air shock. Interestingly, when asked about what they’d like on their next bike, almost half of the riders said they’d consider switching to a coil shock. Though coil shocks are less common, a lot of riders are curious.
Here are some opinions from a few of the top shredders in the shop:
Spencer, Content Marketing Manager - "Coil is too heavy for me and for my riding style. I don't think it makes enough of a difference in performance."
Bruce, Technical Writer - "I do a lot of lift-serviced downhill riding and a few air shocks I’ve owned in the past have failed, lost damping performance, and even burned my leg after heating up to extreme temperatures. I switched to a coil shock and now ride it everywhere."
Asher, Bike Technician - "Air has come a long way in small bump sensitivity, static breakaway force, and heat fade with larger air and oil volumes as well as improved seals. The weight penalty for a coil isn't worth the small and diminishing improvements for me."
Grant, Bike Detailer - "Coil shocks are smoother and more sensitive to small bumps. I think coils are also more supportive in the travel when going up and down tech sections, and heat doesn’t affect the performance of the shock very much."
The Bottom Line
You’ll have to carefully weigh the advantages and disadvantages of each type of shock. In the end, there is no “best” shock option for every rider and every situation. Ultimately it comes down to personal preference, and any shock choice is a compromise. Your ideal shock should be at its best when you need it most. For hardcore downhillers, that probably means a coil shock. For riders who end up earning their turns with long, tough climbs, an air shock might be best.
Which do you ride — coil or air? Let us know why in the comments.
Check out our collection of rear shocks.