Coil Shock Vs Air Shock: Pros and Cons and Which is Best

For years, air shocks have been standard on regular trail bikes and enduro mountain bikes. Coil shocks were reserved almost exclusively for downhill mountain bikes. Some believed that air shocks would replace coil shocks completely. After all, if you walk into any bike shop, you’ll notice that pretty much all the mountain bikes on display come with an air shock. Thanks to some technological improvements and influence from professional racers, coil sprung shocks have begun making a comeback. Particularly among enduro riders. This guide lists the pros and cons of using a coil shock vs air shock for mountain biking. I’ll cover performance, maintenance, adjustability, price, weight, ride quality, versatility, and more. I’ll also explain the similarities and differences between coil and air shocks.

Over the years, I’ve ridden both shock types extensively. My first mountain bike had a coil shock. Later, I switched to air shocks. Recently, I switched back. In this guide, I’ll share my experience.

Table of Contents

• What is a Coil Shock?
• What is an Air Shock?
• Coil Shocks Vs Air Shocks
• Damping Systems
• Pros and Cons Summary

Coil Shocks

Coil shocks use a wound steel or titanium spring to provide resistance. They have a linear spring rate. This means that the amount of force required to compress the spring increases constantly throughout the suspension range. For example, if it takes 500N of force to move the suspension 5cm, it would take 1000N of force to move the suspension 10cm.

The linear spring rate means coil shocks provide less bottom out resistance. For this reason, coil shocks pair best with frames with a progressive spring rate.

Coils are identified with two numbers. The first number is the amount of force required to compress the shock a given distance. This is usually measured in pounds per inch or newtons per millimeter.

For example, a coil shock with a 450lb spring will require 450 lbs of force to compress 1 inch. Coils are available in 25 or 50 pound per inch increments. The second number is the total travel distance of the coil. Most springs have 2-3.5″ of travel (50-90mm).

To adjust the spring rate of a coil shock, you can swap out the metal coil for a stiffer or softer spring. You can adjust the preload and sag by turning a knob on the shock. This compresses or decompresses the coil.

Coil shocks are popular among downhill mountain bikers. They are making a comeback on trail bikes and enduro bikes. Coil shocks are also known as coil-over.

Air Shocks

Air shocks use the compression resistance of pressurized air for shock absorption.

The spring in the shock is provided by compressed air that is sealed in an airtight chamber inside the body of the shock. The air chamber is called the ‘can’. As the air is compressed, it resists further compression. This is called an air spring.

Air shocks have a progressive spring rate. This means that the suspension becomes harder to compress as it travels throughout its range. The stiffness of progressive air shocks increases exponentially.

For example, if the shock requires 500N of force to compress 5cm, it may take 1500N of force to compress 10cm. An air shock can be paired with a frame with either a linear or progressive spring rate.

The spring rate of an air shock is adjusted by changing the air pressure inside of the shock. This requires a special high-pressure pump called a shock pump.

There is a separate control for adjusting the preload and sag of the shock. Most models also allow you to adjust the progression by using spacers to change the volume inside the air chamber.

Air shocks are used in all types of mountain biking. They are the most common suspension design, by far. Air shocks are particularly common on trail and enduro mountain bikes. They are less common on downhill bikes. Air shocks are also known as air springs.

Coil Shock Vs Air Shock

Frame Compatibility for Coil and Air Shocks

Before buying a shock, it’s important to consider the design of the suspension frame you plan to mount it to. Air shocks offer much better frame compatibility. In fact, pretty much all frames are compatible with air shocks. Some frames are not compatible with coil shocks.

This is the case because suspension bike frames come with different leverage ratios. They can have either a linear leverage ratio or progressive leverage ratio design. The leverage ratio is the ratio between the distance the rear wheel travels in relation to the distance the shock travels.

Manufacturers can manipulate the leverage ratio by changing the location and number of pivot points and by using linkages. This allows the leverage ratio to change or remain constant throughout the suspension range. This change in the leverage ratio is called the leverage rate curve.

Adjustability

Air shocks are much more adjustable than coil shocks. They allow you to precisely tune almost every aspect of the suspension’s behavior. For example, you can optimize an air shock for your exact bodyweight, the terrain you plan to ride, and your desired ride feel by adjusting the spring rate, progression, and damping. Air shocks are also much easier to adjust than coil shocks. Coil shocks have far fewer adjustment options. They are more difficult to adjust as well.

Air Shock Adjustment

With an air shock, you can set the exact spring rate or stiffness you desire. This is done by changing the air pressure inside of the shock’s air chamber. Increasing the air pressure makes the shock feel stiffer. Letting air out makes it feel softer. Along with the spring rate, the air pressure also helps to control bottom-out resistance as well as the sag and ride feel of the shock.

You can easily dial in your desired spring rate and sag by changing the PSI in the shock using a shock pump and gauge. This adjustment takes just a few minutes to make. You simply connect the pump to a valve on the shock and push air in or let air out. It’s so easy to adjust the spring rate of an air shock that you can do it before every ride or even stop and do it mid-ride. You can’t do that with coil spring suspension.

You may want to set your air shock’s spring rate to suit the type of terrain you’re riding that day. For example, if you’re riding a bumpy trail, you might let out a bit of air to soften the shock up. This adjustment also comes in handy if you want to carry some heavy gear on your bike or if you gain weight. You can adjust the spring rate to correct for the weight change. You need to set the correct spring rate for your weight.

Air shocks are progressive. As the suspension moves throughout its range, it becomes exponentially harder to compress. You can adjust the level of progression. This is achieved by installing or removing internal plastic volume spacers to change the internal volume of the shock’s air chamber.

This adjustment changes the force required to compress the suspension as it travels throughout its range. In other words, you can fine-tune the spring rate curve to make the shock easier or harder to compress at different points in the suspension range. For example, you can set your suspension so it becomes hard to compress early in the range by adding spacers to decrease the volume of the air chamber. You can adjust the suspension to operate almost linearly until the end of the range by removing spacers to increase the volume in the chamber.

This helps you control the bottom-out resistance and ride feel of the sock. Progression adjustment also allows air shocks to work with a wide range of suspension frame designs with different leverage ratios. Adjusting air suspension progression is easy. You simply let the air out of your shock, unscrew the shock body to access the air chamber (air can), then place or remove spacers.

The ideal progression setting depends on your frame design as well as the terrain you plan to ride. If you are using a frame with a linear suspension design, like a single pivot frame, you would want to set your air spring to be more progressive so it is less likely to bottom out. If your frame has a more progressive design, like a twin link frame, you might adjust the progression of your shock so it operates more linearly.

You can increase bottom-out resistance and change the ride feel by adjusting the progression. If you are riding rough terrain with big drops and jumps, you may want to increase your suspension’s progression to reduce the likelihood of bottoming out during a big hit. Increasing the progression can also make the ride feel a bit more playful or poppy.

A separate adjuster lets you set preload to change the bike’s sag. Many air shocks also allow you to adjust the compression and rebound damping as well.

Coil Shock Adjustment

Coil shocks, on the other hand, are much less adjustable than air shocks. In order to change the spring rate, you must swap out the coil. Coils are typically available in either 25 or 50 lb per inch increments. There may only be 3-4 different spring weights available for your specific shock. It is possible that your ideal spring weight sits somewhere between two sizes.

Coil springs are identified with two numbers. The first number represents the number of pounds required to compress the spring 1 inch. The second number is the total travel distance. Most coils have 2-3.5″ of travel. Keep in mind, this is not the distance your wheel can travel. Your frame controls that.

Changing a coil spring isn’t an easy job. To change the spring rate, you have to physically swap out the spring. This involves taking the shock apart. You’re not going to carry an extra spring and swap them out by the side of the trail. You can’t easily adjust the suspension if you gain or lose weight or decide to mount some bikepacking bags.

Coil shocks have a linear spring rate. On a linear coil shock, the stiffness increases at a constant rate throughout the range. There are no progression adjustments on coil shocks. There are progressive coil springs available if you want progressive suspension. If you want to use one of these, you’ll have to swap out your coil.

One adjustment you can easily make on a coil shock is the preload. You can change the preload to set the shock’s sag. This is done by simply turning a dial on the shock. Many coil shocks also allow you to adjust the rebound damping. Some offer a compression damping adjustment as well.

Shock Weight

On average, an air shock weighs about 300-500 grams (around 0.66-1.1 lbs) less than a comparable coil shock. For example, an average air shock weighs around 350 grams (0.88lbs) while an average coil shock weighs around 800 grams (1.8lbs). That’s a difference of around 400 grams or about 1 pound. An average-sized rider cycling up a 15% grade for 2 miles at an output of 250 watts will take around 10 seconds longer with a coil shock.

Air shocks are lighter because they don’t have a heavy metal coil. The air in the chamber performs the same function and weighs nothing. A lighter bike allows you to accelerate and climb faster and maneuver more easily because there is less mass to move around. It’s also easier to hop a lighter bike off the ground. In cycling, a pound is a pretty significant weight difference.

Coil shock weight depends partly on the spring rate. Shocks with a higher spring rate require thicker gauge metal to make the stiffer spring. This adds weight to the shock. You can reduce the weight of a coil shock by installing a lighter-weight coil. Titanium coils are much lighter than steel. Of course, they are more expensive as well.

The weight difference between modern coil and air shocks is much smaller than it was in the past. Coil shocks are lighter than ever thanks to modern lightweight steel and titanium alloys used to make the coil. Surprisingly, air shocks are heavier than they were in the past due to advanced systems like piggyback chambers and negative springs. These improve performance but add a considerable amount of weight.

Shock Maintenance

Coil shocks require less frequent maintenance than air shocks. The main reason is that there are fewer internal seals. As a result, coil shocks are less affected by dust, dirt, sand, and other contaminants. Coil shocks also don’t heat up as much during heavy use. This allows the oil and seals to last longer. This allows maintenance intervals to be longer. As an added benefit, the performance remains a bit more consistent.

Most manufacturers recommend that you get your coil shock fully rebuilt once every 100-200 riding hours. For the average rider, this equates to around once every 12-18 months. Of course, if you ride frequently, you’ll have to perform maintenance more often. In addition, you’ll want to perform a basic service every 50-100 riding hours or 1-2 times between full overhauls. You should also clean the shock after every ride. This reduces the likelihood of contamination.

Air shocks, on the other hand, require a bit more frequent maintenance. Many manufactures recommend a full rebuild every 75-125 riding hours. For most riders, that will be every 8-12 months. In addition, you’ll want to do a basic service every 25-50 riding hours. You’ll need to perform about 2-3 basic services between full rebuilds. As you can see, maintenance intervals for air sprung shocks are shorter than coil shock.

This extra maintenance is necessary because air shocks have more internal seals. They can get contaminated with dust, dirt, and grime more easily. The seals are also crucial for the shock to function. If the seals that keep the air chamber airtight were to get contaminated or fail, the air would leak out and the shock would stop working. If the seals get contaminated, the oil can also get contaminated or leak out. This would cause damping performance to fade.

In addition, air shocks create more heat than coil shocks because the extra seals create more friction. The heating and cooling of the oil causes parts to wear more quickly. The oil can also degrade. For this reason, the oil and seals need to be changed more often in air shocks. It is also recommended to top the oil up and clean the seals between overhauls.

A complete shock overhaul for a coil or air shock typically involves taking the shock apart, inspecting all of the parts, replacing all of the seals, and replacing the shock fluid. Most riders either ship their shock to the manufacture or take it to a bike shop for a full rebuild. You can’t really do this service at home because some specialty tools and know-how are required.

A basic service involves inspecting the shock for wear or damage, topping up the fluid, and replacing the air sleeve seals if you’re using an oil shock. You can perform a basic service on your coil or air shock by yourself or take the bike to a shop. You should also wipe down the shock after every ride to reduce the liklihood of seal contamination.

If you don’t properly maintain your shock or you neglect maintenance, it will eventually get contaminated with debris. The seals will begin to leak and the oil (and air) will leak out. Abrasion from debris rubbing against internal parts as they move can also cause unnecessary wear and tear. Your shock will wear out prematurely if you don’t maintain it and keep it clean.

For more info on shock maintenance, check out this great guide.

Heat Fade

When a shock continuously compresses and decompresses, friction between the seals and moving parts cause the system to heat up. Excessive heat build-up causes shock performance to degrade. This is known as heat fade. This affects both the spring rate and damping system of the shock. This problem is particularly common while riding down long bumpy descents that take longer than around 20 minutes. Downhill mountain bikers have to be careful that they don’t overheat their shock.

Coil shocks manage heat much better than air shocks. They do not heat up as quickly and they do not create nearly as much heat. As a result, coil shocks generally don’t suffer from heat fade. Performance remains consistent.

The reason coil shocks don’t suffer from heat fade is that there are fewer seals creating friction. The metal coil spring itself requires no seals and has no moving parts so it stays cool. As a result, the spring rate of the coil does not change during a long descent. Because there are fewer seals, the oil in the damping system of coil shocks stays cooler as well. This allows the damping performance to remain more consistent. For these reasons, most downhill mountain bikers prefer coil shocks. They can ride down long descents without having to worry about their shock overheating.

Air shocks, on the other hand, require tight seals to keep the pressurized air inside. They have more seals as well. The seals create friction in the system, which heats the shock up. This heat also causes the oil in the damping system to heat up. This can change the oil’s viscosity. The fluid becomes thinner, which makes the damping system less effective. The thin oil can more easily flow through the ports in the shock as it compresses and rebounds. This makes the ride a bit more rough and bouncy. That said, modern oils are pretty resistant to viscosity changes.

When air shocks heat up, the air inside the chamber also expands. This increases the pressure, which increases the spring rate. The seals inside can also expand slightly when they get hot, making them tighter. The shock become stiffer as a result and can’t compress as far. This increased pressure changes the shock’s progression as well. For these reasons, air shocks are not ideal for downhill and freeride mountain biking. The heat buildup makes the shock stiff and bouncy.

The heat can be dangerous as well. Air shocks can actually get so hot that they can burn your leg. Feel the body of the shock after a long descent if you currently use an air shock. If it’s hot, you may be better off switching to a coil shock. If you ride in an extremely hot climate, you might also be better off with a coil shock. Outside heat combined with heat created by the shock can cause performance to fade. That said, most recreational riders will never ride hard or fast enough for heat to be an issue. If your shock overheats, you can just take a break and let the shock cool off. For competitive riders, heat build-up can be a serious problem that can affect speed.

Air spring shock technology has been improved over the years to better deal with heat. Modern models have larger volume air and oil chambers that allow for better cooling. This greatly reduces heat fade. Most modern air shocks also have internal floating pistons (IFP) that move the oil and gas (usually nitrogen) away from the main part of the shock. This allows heat to dissipate more easily.

Piggybacking shocks also have two compression circuits. This splits up the load so less heat builds up in the damping system. Manufacturers are also finding ways to reduce friction so the shock creates less heat to begin with. Modern high-end air shocks deal with heat very well. That said, coil shocks still offer better performance on long descents because they don’t create nearly as much heat.

Small Bump Sensitivity

Coil shocks are more sensitive to small bumps than air shocks. This is possible because coil shocks contain fewer seals. Some of the seals fit looser as well because the shock doesn’t need to be airtight. Fewer seals means there is less static friction or stiction in the system. Stiction is caused by friction from the seals rubbing against moving parts such as the shock shaft.

Sufficient force is required to overcome stiction in order for a stationary shock to begin moving. The amount of force required to break the stiction and make the suspension begin compressing is called breakaway force. Coil shocks require less breakaway force than air shocks. In other words, the impact threshold for coil shocks to begin moving is lower. This allows coil shocks to be more sensitive to small bumps than air shocks. This is sometimes referred to as off the top sensitivity.

A coil shock can soak up a small bump that an air shock wouldn’t even react to because the coil shock requires less force to break the stiction and begin moving. When you hit a bump, a coil shock can also react faster. This gives coil shocks a smoother and more supple ride feel. As an added benefit, the better small bump sensitivity of coil shocks allows the damping system to do a better job because it can begin working more quickly and with less force.

Air shocks, on the other hand, aren’t quite as sensitive to small bumps because they have more seals. Some of the seals must fit tighter because they need to hold pressurized air inside the shock in order for it to function. This increases stiction. It takes more breakaway force to get an air shock moving. An air shock may not react to a small bump that doesn’t create enough force to break the stiction. They also can’t react quite as quickly to bumps. This makes the ride feel a bit more harsh. The damping system can’t work quite as well either because it can’t respond as quickly to an impact.

To help solve this problem, newer air shocks feature a large negative spring. This negative spring opposes the air spring when the shock is fully extended in its resting state. The negative spring assists the shock to overcome the static friction so it can provide better small bump sensitivity. In other words, it reduces the amount of breakaway force that is required to get the shock moving.

A well-designed air shock with a large negative spring offers almost the same small bump sensitivity as a coil shock. Some modern coil shocks also have a negative spring. For more info on negative air springs and how they work, check out this article.

Traction

Coil shocks offer better traction than air shocks. This is possible due to the superior small bump sensitivity. The rear wheel can track the contours of the ground better and more consistently when the suspension is more sensitive to bumps. The linear spring rate curve of coil shocks also makes the suspension feel a bit more responsive. Particularly while riding rough sections of trail. This also helps to improve traction.

Increased traction allows you to take corners harder and faster without having to worry as much about your wheel sliding out from under you. The bike sticks to the trail better. The bike also feels more stable while riding over bumps. The increased traction also allows you to brake a bit harder without skidding your tire. This all inspires confidence. Coil shocks are great for riding trails with loose surfaces or lots of curves.

Air shocks don’t provide quite as much grip. The reason is that they can’t absorb some small bumps due to stiction. As a result, the rear wheel can’t track the ground as consistently. It bounces around a bit more. When the rear wheel is bouncing around, traction decreases. After all, your wheel can’t provide grip when it’s bouncing off the ground. You may not be able to corner quite as hard with an air shock. On rough stretches, you might have to ride a bit slower so you have enough grip.

Bottom Out Resistance

Air shocks provide better bottom-out resistance than coil shocks. The total amount of force it takes to compress an air spring and bottom it out is greater than a coil shock. This is possible thanks to the progressive spring rate of air shocks. As the shock compresses through its range, it becomes exponentially harder to compress further. The spring rate ‘ramps up.’ Toward the end of the suspension range, it takes an enormous amount of force to further compress the air inside of the shock. This reduces the likelihood of the shock bottoming out during a hard hit, large drop, or after landing from a jump.

Air shocks also allow you to easily adjust the bottom-out resistance. There are two ways to achieve this. The first option is to decrease the volume in the air chamber by adding some spacers. This makes the suspension more progressive. The suspension becomes harder to compress earlier in the range and is more resistant to bottoming out as a result. This feature allows air shocks to pair with frames with a linear leverage rate. The shock can provide progression to reduce bottom outs instead of the frame.

The second way to increase bottom-out resistance is to increase the PSI in the air chamber with a shock pump. This increases the spring rate and stiffens up the suspension so it is harder to compress and bottom out. If you plan to ride a rough trail with lots of drops or jumps, it’s a good idea to crank up the bottom-out resistance by increasing the air pressure or progression.

Coil shocks can bottom out more easily than air shocks because spring rate is linear. The amount of force required to compress the metal spring increases constantly throughout it’s range. The total amount of force required to fully compress the shock and bottom out is less than an air shock (assuming both shocks are adjusted for the same rider weight on the same frame).

During a drop, jump, or hard hit, you can fully compress the spring and bottom out a coil shock. You’ll know when this happens because you’ll feel a hard stop and hear a thud when the suspension stops traveling. It is particularly easy to bottom out a coil shock on a frame with a linear leverage rate because neither the frame nor shock provide any progression. Coil shocks pair best with frames with a progressive leverage ratio. I’ll talk more in-depth about this later.

Regardless of which type of suspension you use, chances are you will bottom out once in a while during a particularly hard hit or drop. If you jump your bike, the risk of bottoming out increases. Bottoming out around once per ride is normal. Almost all modern shocks have some type of bottom-out protection built-in to prevent damage to the shock. This is usually a rubber ring that prevents metal on metal contact inside of the shock during a bottom out.

If you bottom out too hard or too frequently, you can cause damage to your shock or frame. Eventually, your suspension’s bottom-out support will wear out. A particularly hard hit could bend a wheel or even bend your bike’s frame. You want to adjust your suspension so bottom outs are rare. If you’re bottoming out too often, increase the pressure or progression in your air shock or install a stiffer coil spring to your coil shock. If you never bottom out, you may be able to loosen up your suspension a bit. It may be too stiff.

Coil and Air Shock Cost

Coil shocks are usually slightly more expensive than air shocks. You can buy a mid-range to high-end coil shock for $500-$650. Air shocks cost around $400-$600 on average.

When calculating the cost of a shock, it’s important to consider the maintenance cost over time. Coil shocks require less frequent maintenance. For this reason, they are usually cheaper in the long run. If you ride an average amount, you might save $100 per year on maintenance if you go with a coil shock.

Full shock service generally costs around $150. This involves a complete cleaning and rebuild with all new seals and oil. Most manufactures recommend you get your coil shock serviced every 100-200 hours or once every 12-18 months.

Air shocks generally need to be serviced a bit more frequently. This is because the seals need to be replaced more frequently to keep the shock airtight. Most manufacturers recommend a full service every 75-125 hours or every 8-12 months. The frequency depends on how often you ride and the manufacturer of your shock. The more frequent rebuilds adds to the cost of ownership of air shocks.

Shocks also need basic service between full services. This involves topping up the oil, cleaning or replacing the seals. This service costs around $30-$50. You can do this yourself for a lot less if you buy some basic tools and parts. Coil shocks generally need one basic service between full services. Air shocks might need 2 or 3 basic services between full services. The shorter maintenance intervals of air shocks adds to the cost of ownership.

Neglecting maintenance will increase the cost of ownership over time as well because your shock will wear out sooner. Generally, coil shocks deal with neglect better than air shocks. If you’re buying a used bike, you’ll want to ask the owner how often the shock was maintained.

One extra expense you may have if you ride a coil shock is a new spring. This will be necessary if you want to have the ability to change your shock’s spring rate for riding different terrain. Coil shock springs cost anywhere from $20 to $130 depending on the quality, design, and material they’re made of. Titanium springs are more expensive than steel, for example. If you’re only able to own one bike and you use it for trail riding, bikepacking, and downhill riding, you might need a few different coils. The cost can add up. Of course, you don’t need to buy multiple springs. You can just set your s