Trutune Air Fork Insert boutique-mtb
Trutune Air Fork Insert boutique-mtb
Trutune Air Fork Insert boutique-mtb
Trutune Air Fork Insert boutique-mtb
Trutune Air Fork Insert boutique-mtb
Trutune Air Fork Insert boutique-mtb
Trutune Air Fork Insert boutique-mtb
Trutune Air Fork Insert boutique-mtb

Trutune Air Fork Insert

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Plug and play insert for mountain bike air forks, powered by Activated Carbon. Increases effective air volume and reduces speed sensitivity for a plush, linear and consistent feel. See below for more information.  


Activated carbon plug-and-play insert that installs like a token, but acts to increase the effective air volume of your fork, resulting in a more linear spring curve. Our first edition inserts are assembled in our workshop, and tested and validated with our dynos and our team of test riders. 


  • Reduces air stiffness, for better small bump sensitivity, comfort, and grip without compromising sag 
  • Makes the spring force more linear, closer to a coil but with the adjustability and weight advantage of air
  • Permits greater use of travel when charge pressure is unchanged - lighter riders can make full use of their suspension  
  • Initial suppleness drastically reduces chatter, lessening arm pump and fatigue
  • Makes the fork more consistent and predictable by dramatically reducing speed sensitivity
  • Pairs very well with negative chamber upgrades (e.g. Vorsprung Secus, Everflow Tank) to provide an exceptionally linear and consistent feeling through the travel


Our Standard length inserts are designed for the greatest linearity, and suit most riders and general trail riding. There are, however, a few reasons to choose our Short variants, which are a little more progressive and shorter, allowing more spacers to be used in combination and providing better bottom-out resistance. The first is compatibility: if our Standard length is too long for your fork and travel (based on the manufacturer token limit), then our Short insert is usually the only option. If either is compatible, then if two or more of the following apply the Short variant will be more suitable for you:

  • Heavy rider (over 90kg with gear)
  • Ebike
  • Run 3 or more tokens as your preferred setup
  • Run high pressure (100psi or more)
  • Aggressive style
  • Typically ride trails/bike parks with large jumps where extra bottom-out resistance is needed 


The activated carbon contained in our inserts acts to increase the effective positive chamber air volume in your fork. This happens due to its high porosity and internal surface area, which traps and releases air molecules, mitigating changes in pressure (more information on that process can be found on our Technology page). The effect is similar to what happens when you remove tokens: the spring rate is more linear, with less ramp-up. This may be hard to believe because it is a solid material after all! You can see a demonstration of the effect on measured pressure in the video below when compared to regular volume-reducing tokens. With tokens, the pressure at the end of the stroke is higher, while with our insert it is lower, even compared to no tokens at all! 

The increase in effective volume is not the only effect of activated carbon. The air in a fork is speed sensitive: fast compression results in higher pressure, and so higher stiffness, compared to slow compression. The activated carbon in our inserts exchanges heat with the air, which mitigates the temperature changes in the air and dramatically reduces its speed sensitivity, resulting in a more consistent and predictable feeling. 

When using our inserts, the charge pressure is usually increased, to achieve similar pressures at the end of stroke compared to the original setup. This results in the right amount of support, but with improved tracking, bump absorption, and comfort provided by the more linear spring rate.


TruTune inserts come in a specified equivalent number of tokens. Do not exceed the manufacturer-specified maximum number of tokens/spacers for your fork model. If in doubt, contact our suspension specialist TruTune tester at 

Fox 32 4
Fox 32 Rhythm, FLOAT (PINK / BLUE spacers)
Fox 34 E-Bike
Fox 34 4 Fox 34 Rhythm, Step Cast, FLOAT (GREEN spacers)
Fox 36 Rhythm FLOAT NA2 (PURPLE spacers)
Not compatible with E-bike 34 forks
Fox 36 / 38 Standard: 5
Short: 4
Fox 36 FLOAT NA2 2018+ and
Fox 38 FLOAT (ORANGE and YELLOW spacers)
Not compatible with Fox 36 Rhythm FLOAT NA 2 (PURPLE tokens) - our Fox 34 model should be used.
RockShox 32mm 3
32mm Rockshox DebonAir(+)
Equivalent to BLACK bottomless tokens
Not compatible with Dual Position Air springs.
RockShox 35/38mm Standard: 4
Short: 3
35mm and 38mm Rockshox DebonAir(+) (ZEB, Pike, Lyrik, Yari)
For SID 120mm choose the Short variant.
Equivalent to GREY / RED bottomless tokens
Not compatible with Dual Position Air springs.



WARNING: modifying any aspect of your suspension without the appropriate training and experience can result in serious injury or even death. Installation should be carried out by a competent technician. We cannot be held responsible for the results of the incorrect installation of our product and assembly of your suspension.

The following are guidelines for installing Trutune plug-and-play inserts for mountain bike front air suspensions. Please refer to the fork manufacturer manual for up-to-date instructions on assembly/disassembly for your specific model.

    • Firstly, secure the bike in a suitable stand to ensure the bike is safe to work on. If the forks are separate from your bike, use a suitable vice or the clamp from a bike stand with soft jaws to avoid damage to the forks or bike.
    • Unscrew the dirt cover to expose the valve and put the cover in a safe place.
    • Using a small tool (Allen key) remove ALL the pressure by gently pressing the valve.
    • Using an appropriate socket or cassette tool (depending on year/model) remove the top cap, gently applying pressure to ensure the tool does not slip.
    • Once the top cap is removed, remove ALL plastic volume spacer tokens. OEM tokens can be used in conjunction with a TRUTUNE insert, however, it is important that the number of tokens plus the token length of the TRUTUNE insert does not exceed the manufacturer's specified maximum number of tokens for the fork.
    • Securely attach the insert to the top cap (for RockShox forks, this will generally be a screw thread, for Fox forks a snap fit).
    • Apply a small amount of grease to the cap o-ring and then Install the top cap with the TRUTUNE insert into the air chamber and tighten to the manufacturer-recommended torque using a torque wrench
    • Using your air pump, pressurise the positive air chamber to your desired pressure, or alternatively consult the manufacturer pressure charts for your fork model and weight. Allow 30 seconds for the pressure to settle, as it will drop slightly after charging, and top up to the right value, ensuring to pump the fork a few times to equilibrate both chambers. With a TRUTUNE insert installed, we recommend to increase pressure by 5% above the preference/manufacturer recommendation as a starting point. 
    • With the aid of the floating o-ring on the fork (if available), ensure the ride sag position is within the manufacturer's specification (or personal preference). If not, increase or decrease pressure as appropriate.  
    • Finally, replace the dirt cover onto the top cap valve carefully to finger tight.

To ensure performance is maintained over time, when kept outside the fork, store Trutune inserts in cool and dry conditions, and avoid exposing to water, oil or other contaminants. Your bike may be stored upside down with a Trutune insert provided the quantity of lubricant does not exceed the amount specified by the fork manufacturer. When servicing the fork, do not exceed the manufacturer's recommended quantity of lubricant and grease as this may affect the performance of the insert. 

Setup Guide

WARNING: modifying any aspect of your suspension without the appropriate training and experience can result in serious injury or even death. Installation should be carried out by a competent technician. We cannot be held responsible for the results of the incorrect installation of our product and assembly of your suspension.

These guidelines are based on our test program so far and will be updated as we learn more from rider feedback. Our recommendation depends on your current setup, riding style, and weight. For all riders, the starting point is to remove all tokens/spacers you currently have and use a Trutune insert on its own. When charging the fork, allow 30 seconds for the pressure to settle after the chambers have equalized.


After installing the insert, start with 2-5% more pressure than your usual setup. If you feel a lack of support or are bottoming out the suspension too easily, increase air pressure in small steps (3-5 psi) until you find the right balance of plushness and support. It may be necessary to increase the rebound speed on your damper (if the setting is available) to help with hold-ups.


If you struggle with using all the travel of your fork, and/or tend to run low pressure, and/or have a stiff fork when set at your preferred sag position, we recommend charging to the same pressure (or only 1-2% higher to match sag position) as your usual setup as a starting point, which will simply make more travel available and increase your comfort and grip.


The starting pressure required may be over 10% of your usual setup. Some riders in these categories have found 15 or even 20 psi higher to be the right balance. If the increase in pressure is still not sufficient, causes unacceptable initial stiffness, and the fork is bottoming out too easily, then we recommend combining the TruTune insert with one OEM volume spacer (if the total length does not exceed the maximum number of spacers for your fork model / travel).

If you are not happy with your setup or not satisfied with the performance, Trutune team are here to help, please get in touch with them at

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