I have not bought one yet, and I am very new to the sport. The type of riding I will be doing is dirt jumps (rather large ones) and rugged trail riding. I used a BMX for these things previously, which actually worked out pretty well. As a newbie to the sport, I am just wondering: which type of rear shock would be best to look for: air, or coil?

I want something that is going to be easiest to maintain, and most efficient while riding. A bike I have been looking at is the Scott Voltage FR 30/20/10 models (these all have a spring rear shock) or a Trek Slash 9/8/7 model (which have a hydraulic type shock). I am leaning towards the Scott Voltage bikes, they look simpler, but I am unsure.

4 Answers 4


You're mixing up two different concepts.

The damper, which is what slows things down. The spring, which is what holds the weight and absorbs shocks.

The damper is usually hydraulic, oil being forced through a small hole. The spring is either a coil or pressurised air.

Without a damper, you'll have a very bouncy ride and without a spring, you'll have a very stiff ride. The 2 work together to provide a nice ride.

Also, those 2 bikes target different styles of riding.

The Slash is an Enduro bike and the Voltage a Freeride bike.


First step: clear the confusion. As other answer states, the spring and the damper are complementary systems that work together in order to provide the desired ride characteristics. As for bike suspenssion regards, there are two main kinds of suspension components, based on the type of spring: Coil and Air. Most suspensions have hydraulic dampers regardless of the spring type.

Second step: To each its own. Asking wether air or coil is beter can get you in those kind of almost religious debate. Instead, I'll try to expose a few points of comparison so you can make a better decision:

Air Spring:

  • Weight less than coils.
  • Are easily adjustable to a broader range of rider weight/activity type/ride skill or technique.
  • Have a cleaner, simpler look.
  • Most of them require a special pump to increase the spring preload (reduce sag).

Coil Spring:

  • Usually have a lower cost.
  • Are heavier than air springs.
  • Most can have the preload/sag adjusted by hand.
  • Have a narowwer range of adjustment, to make further adjustment the coil has to be replaced by a different one, wich may not be easily obtainable in your particular location or may not be available from the manufacturer.
  • Have a messier look and require a little more dedication for routine cleaning.

Further up, it is more important wether the shok absorber is the correct fit for the bike frame and the discipline in wich it will be used. For example, a shock designed exclusively for XC may never excel on DH for a normal wheigted rider. If you are buying a complete bike directly from the manufacturer or a reputable dealer, they should only offer the correct shocks for the frame, so it's up to you to choose a bike that fit your intended use. Also if the same bike is available with different shock options, make sure the one you pick is suitable for your riding.

Finally, getting the right equipment is only the beginning of a customizing process. If you are changin the type of bike, you will have to go throug a fitting and fine tuning cycle that will be somewhat affected by your own ability to adapt to a new geometry, weight and ride characteristics. This process involves fine adjustments to the shocks. Most shocks have at least these adjustments:

  • Preload (or how stiff the shock feels)
  • Rebound speed (how fast the suspension returns after a bump).

Some specialized shocks may have more adjustments. In either case, read the shock specific user manual for the model you get.

All of the above also applyes to MTB suspension forks, except for the looks and the routine cleaning part.


I know these "answers" are unrelated to the actual question you asked, but I just needed to put my two cents in. First, it's going to be a huge change if you're actually planning on using a huge 170+ travel bike like the Voltage for something you used to do on a BMX. Not trying to shut you down, just a word of warning. Second, "trail riding" usually implies that you're going to be doing some uphill pedaling. You may have just been using the wrong word to describe the type of riding you plan on doing, but trying to get a freeride bike up a hill can be pure hell. Usually if you're going to buy such a bike, you plan on going somewhere with a lift to the top or having someone shuttle you. TL;DR For dirt jumps, get a dirt jumper. For trails, get a trail bike. If you absolutely need a single bike to rule them all, an enduro bike such as the Slash may serve you well. All depends on your personal preferences. If you can test ride before you buy, whether through your local bike shop or at a demo event, definitely do that. You can get a feel for how different bikes as well as different shocks feel.


A hydraulic shock will have better damping...which is what a shock is supposed to do: dampen the hits to your suspension. Hydraulic shocks still have an air spring. Spring shocks are the cheaper way to go - just not as good. High end bikes will have a hydraulic shock.

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