MTB Air Fork Upgrade


    🔧  Support with setup

    🤙  Money back guarantee*

    🛒 Get 2+ (including HIT) for 15% off


NOTE: We no longer offer two options for Fox 36/38 and Rockshox 35/38. These are a single model corresponding to the old "Short".

compliance without compromise

Reduce fatigue, increase grip and comfort. Experience a coil-like feel without the weight penalty.

The TruTune Flow is a plug-and-play upgrade for mountain bike air forks. Powered by activated carbon, it increases effective air volume and reduces the speed sensitivity of air.

The result? Better small bump compliance, increased mid-stroke support and end stroke absorption.



Installs simply, just like a volume spacer. Release all pressure, remove the top cap, clip on or thread on the insert, and charge to our recommended pressure.


Smooth and comfortable feeling through the whole travel, reducing arm pump and fatigue and providing improved grip.

Provides a consistent stiffness, similar to a coil spring. This allows running higher pressure for exceptional support without running into harshness, or keeping pressure the same to unlock more travel.



Reduces speed sensitivity inherent in air springs, meaning the fork feels more predictable and does not stiffen up with faster movements. This is critical to reducing chatter and improving end stroke absorption.





build the ultimate combo

Get 15% off by combining with our HIT piston upgrade for a complete coil-like transformation through the entire travel, with the adjustability and weight advantage of air.

Pre-order HIT now

Customer Reviews

Based on 98 reviews
kitt morris
Fork: Fox 36 Rhythm 150mm
Don't have to buy a new fork.

Having changed bikes, and also fork brands from Rockshox Lyrik to Fox 36 Rhythm, was trying to get that super plush feeling of the Rockshox back. Even with no tokens and lower pressure, just couldn't quite get what I wanted from the fox, including full travel. I weigh 80kg so not particularly light weight, but that Lyrik spoilt me. Reading reviews of the Tru Tune insert got me interested as wanted to keep the fork I had if possible, so when it was on sale I gave it a go. Have to say it's been exactly as described and has made it much easier to get pressure set up on fork perfect for my taste. Now my Trek Fuel Exe feels much more balanced with what is classed as the budget version of the Fox range of 36 forks.

U. Schall
Fork: Fox 38 factory grip 2
It works 🤘🏻

on the first trails, it feels like the forks works smoother. in the next couple of weeks, I will see how it works on black diamond trails

Fork: 2023 Pike Ultimate
Still Tweaking

I must warn you that it is VERY easy to cross thread the rather soft threads of the Trutune when installing on Rock Shox forks, though I was being very careful. I had to take a sewing needle to run along the depth of the threads to straighten out the first couple threads, but on the third attempt, I was able to finally thread it properly.

As for the performance, I did have to increase the preload an additional 10 psi. I thought I had the rebound figured out but when I hit a couple jumps, the front end took somewhat of a nose dive causing me to almost go over the bars. It didn’t seem to rebound quick enough with the Trutune, so I’m still trying to figure that out.

They claim to get better traction but I didn’t notice it. It did see to provide a more supple compression from the mid to the end of the compression stroke, which is why I purchased it to begin with, I just need to figure out the rebound and the high speed compression.

Brandin Bowler
Fork: 170mm zeb
Does exactly what it says it does.

Was surprised to see how well it worked as a negative token. Zeb fork was way too progressive even with no tokens for my girlfriend. Installed the trutune and she can more easily access her travel.

David Tyler
Fork: Fox 36 Rhythm
Fitted to a Fox 36 Rhythm Fork

Being a lightweight rider (60KG) I felt I wasn't getting the best from my fork. The fork only used about 2/3rds of travel and on bumpy surfaces it feels like it locks up mid travel.

Once fitted (a two minute job) I could immediately feel the difference. It was soooo much better. Like night and day better.

I had access to full travel and it felt much better over rocky terrain. You could literally hammer over everything!

I no longer feel the need to upgrade to expensive forks with a grip 2 damper. In fact I prefer the Grip damper because I can lock out the fork for climbs.

I will definitely invest in the hit negative damper when it is released and fit the flow to my Rockshox 32 ultimate fork.

Hopefully TruTune will also do something for rear shocks.


TruTune inserts come in specified equivalent number of tokens. Do not exceed the manufacturer specified maximum number of tokens / spacers for your fork model. If in doubt, contact us at info@trutune.co.uk.

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 incorrect installation of our product and assembly of your suspension.

Rock Shox, Fox, Rhythm, FLOAT, DebonAir, Dual Position, Pike, Lyrik, Yari, Reba, Bluto, Revolution, SID are registered trademarks and propery of their respective owners. All company and product names used in this website are for identification and compatibility purposes only. Use of these names, trademarks and brands does not imply endorsement.

in the media...

pinkbike magazine

"trutune suspension inserts unlock more travel"

"When I first heard about it, I thought it was a joke, but after talking to the engineers at Carbon Air, the company behind TruTune, I realised the physics was sound. Now I've had the chance to ride it and, at the risk of giving away the ending of this review too soon, it does what it promises."

singletrack magazine

"the tardis token"

"With the TruTune installed I can finally get modern big negative air chambered fat-legged forks to perform better. It doesn’t give you everything that a coil fork does but it certainly improves things massively. If your bike has a 38mm fork on it that you can’t quite get to do the things you need it to do, a TruTune MTB AIr Fork Insert is totally worth a look."


TruTune form part of the setup on the Pole Voima reviewed on Pinkbike magazine.

"I called in a Carbon Air insert to make the Zeb more linear and upped the pressure to 72 psi. This allowed me to use more of the travel on big hits while sitting a little higher in the travel, which better matched the feel from the rear."

Read Article


Our technology was nominated for Pinkbike's innovation of the year 2021, after our prototypes were tested by Seb Stott.

"This one's a lot harder to explain. I thought it was a joke when I first heard about it. But Carbon Air has been used in the air suspension of Audi's luxury sedans for years.In short, its aim is to make air suspension work more like a coil. It does this by using activated carbon, which can be made from sawdust and has the counter-intuitive property of mopping up more molecules of air per cubic centimetre than the same volume of empty space. It acts as the opposite of a volume spacer - effectively increasing the volume of an air chamber."

Read Article


Use of TruTune components may invalidate any warranty with the original equipment manufacturer.

Rock Shox, Fox, Rhythm, FLOAT, DebonAir, Dual Position, Pike, Lyrik, Yari, Reba, Bluto, Revolution, SID are registered trademarks and propery of their respective owners. All company and product names used in this website are for identification and compatibility purposes only. Use of these names, trademarks and brands does not imply endorsement.