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.  

SUPPORT WITH SETUP 

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. 

WHAT IT DOES FOR YOUR RIDE

• 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

CHOOSING BETWEEN STANDARD AND SHORT

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 

HOW IT WORKS

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.

Compatibility

  

Installation

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.