The RUNT Fork Add-On is an air spring system that threads into the top air chamber of your FOX 36, RockShox, Lyrik, Pike, Yari, and Revelation fork, replacing any volume spacers. The patent-pending design provides coil-spring-like performance from your air sprung fork, creating a near linear compression curve while maintaining infinite adjustability.
This is the RUNT Fork Add-On?
- Easy drop-in installation
- Half the price of a coil conversion
- 1/2-pound lighter than coil conversions and only 20 grams heavier than the same amount of tokens or spacers
- Does not ruin your fork
- Infinite adjustability / built-in tunable bottoming resistance
- Complete package – Comes with shims to custom tune your damper to your body weight for most forks if desired.
- MSRP $200 USD
- RockShox Pike, Lyrik, Yari, and Revelation Solo Air Charger 1 or Charger 2 forks (35mm, Boost and non-Boost)
- FOX 36 GRIP 1, GRIP 2, and FIT 4 forks (2018 and newer)
What Is Optimal?
Your shock has three sections of travel. Initial, Mid, and the End. For you and your bike to perform to your fullest potential, there are optimal characteristics to each one of those sections of travel. They are as follows:
Optimal Initial Stroke – Traction is dependent on your tire maintaining continuous contact on the riding surface, therefore optimally your suspension’s initial stroke should be as supple as possible for small bump sensitivity.
Optimal Mid Stroke – Cornering is completely dependent on support in the mid-stroke. If the suspension curve is too low through the mid-stroke, your cornering will suffer drastically as the front end of your bike will dive and your geometry will change. Proper mid stroke support also helps keep your fork from diving while descending. This helps preserve your geometry making your bike more stable.
Optimal Ending Stroke – The RUNT Fork Add-On offers adjustable bottoming resistance without compromising your initial or mid-stroke.
What The RUNT Fork Add-On Solves
A steady linear compression is the holy grail of air suspension. The most common problem with an air fork is the tendency to have an overly supple beginning and mid-stroke, and then a drastic spike in compression towards the end. This contributes to a less than optimal suspension set up, either sacrificing small bump plushness for stiffer cornering performance or vice versa. The RUNT Fork Add-On solves this.
As demonstrated in this animation, The RUNT Fork Add-On is set to a specific psi. When the air spring’s pressure reaches the same pressure in The RUNT, The RUNT’s floating piston begins to move. This allows for a linear pressure curve previously impossible in air sprung forks.
If you need increased bottoming resistance simply increase the pressure in the high chamber. Increasing bottoming resistance will not affect your initial stroke and only slightly affect the end of your mid-stroke.
Frequently Asked Questions
Q: Do I need to re-valve my damper for The RUNT to work?
A: No, The RUNT Fork Add-On works well as a drop-in and will be an improvement to your ride. That said, we have been re-valving forks for years as they are not very supple from the manufacturers. Re-valving makes your fork ride even better! The RUNT Fork Add-On is shipped with shims to re-valve your rebound damper and/or your entire damper. On some forks the lock-out feature becomes less effective. Your local bike shop can do this for you or you can send it to us. Many riders choose to take this one step at a time.
Q: Is The RUNT hard to install?
A: The RUNT Fork Add-On is super easy to install. You simply remove the air in your left fork leg, remove the top cap and any spacers or tokens, screw The RUNT in, air it up, and you are ready to ride. The process takes about five minutes.
A: The RUNT Fork Add-On, unlike other options out there, is fork travel specific and was designed to take up the maximum air volume in your fork leg. We do have flat and step pistons that allow you to convert between 150mm and 160mm of travel, for example, by ordering a different piston.
Q: What maintenance does The RUNT require?
A: The RUNT Fork Add-On requires very little maintenance. Once a year we suggest replacing and lubing an o-ring contained inside. That’s it!
Visit the Diaz Suspension Design website for more details.
Credit: Diaz Suspension Design