HIT

pre-order now for £10 off

Shipping from 3rd June '24

MTB Air Fork piston Upgrade

£89.00

£99.00

🔧 Support with setup

🤙 Money back guarantee*

🛒 Get 2+ (including Flow) for 15% off

Model

Fox 36 FLOAT NA2 2018+

Fox 34/38

RockShox Lyrik 2023+

RockShox ZEB

Orders including a HIT piston will ship when HIT becomes available.

hit new heights

The TruTune HIT is a piston upgrade kit for mountain bike air forks. Powered by activated carbon, it increases effective air volume and reduces the speed sensitivity of air.

Targeting the negative chamber results in better small bump compliance, increased mid-stroke support and higher ramp up.

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Plush off the top
Improved traction and support
Compliance without compromise

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plush with extra ramp up

Precision target the initial stroke for an incredibly linear and supple off-the-top feeling. Run higher charge pressure for a steep - but not excessive! - ramp up for all the support you need. Benefit from low speed sensitivity in the initial stroke for extra comfort and chatter elimination.

build the ultimate combo

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

Shop Flow

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DOES THE piston FIT ON MY FORK?

Check the compatibility table, which will be updated regularly. If you are still not sure about fitting, contact info@trutune.co.uk.

WHEN WILL IT BE AVAILABLE IN MY COUNTRY?

Our inserts are shipped worldwide. If no shipping options are available for your country, let us know at info@trutune.co.uk.

HOW CAN ACTIVATED CARBON POSSIBLY INCREASE THE EFFECTIVE AIR VOLUME?

It may seem counterintuitive, but adsorption is how this happens. As the fork or shock is compressed, some air adheres to the surface of the carbon. The air adhered to the carbon can have much higher density, and so reduces the pressure in the rest of the gas (compared to a chamber without any activated carbon). You can find out more on our Technology page.

is it the same as other piston upgrades on the market?

The HIT piston contains activated carbon. As well as providing increased effective volume, it also reduces the speed sensitivity inherent to an air suspension. The result is much greater compliance than simply increasing air volume, helping to provide a lot better small bump sensitivity and a more predictable feel.

is the activated carbon affected by moisture?

The effect is influenced by moisture, as water vapour competes with air in attaching itself to the carbon surface. In the sealed fork chamber, the amount of moisture is not sufficient to influence the effect or degrade performance over time. Provided the piston is stored in dry conditions when out of the fork the performance will not be affected. Even after exposure to high humidity, the difference in performance is small as the surface area available for the air molecules at high pressure is still very high.

Does the carbon release powder or dust into the fork?

We use a fine filter that we have selected out of many, having subjected it to shakers, test riding and dyno testing to ensure that there was no build-up of powder over time. We also apply a coating to the carbon to minimise powder production and allow a tight pack of granules in our products, reducing internal movement.

is the effect dependent on temperature and pressure?

The effective increase in volume is temperature dependent, with around 5-10% variation between 0 and 40C. This is a small difference In terms of total fork volume, and so does not cause a dramatic change in feeling. The air pressure in the fork is slightly more sensitive to temperature than a regular air spring - the reason for this is that the carbon stores air in its pores which can be released by heating (and vice-versa trapped by cooling). The net effect in the fork depends on the amount of material, so we have found the right balance based on our test riding. The effect is also dependent on charge pressure, with higher pressure resulting in a smaller (but still stiffness reducing) effect. The pressures at which the activated carbon is no longer effective are much higher than those found in MTB air suspensions, including shock absorbers.

IS THE ACTIVATED CARBON AFFECTED BY SUSPENSION OIL AND GREASE?

When activated carbon is used in filters, substances accumulate and saturate the carbon as contaminated air or water flows through, and so over time the filters become less effective and need to be replaced. In the sealed environment of the fork, the only contaminants that can affect the behaviour are suspension oil and grease, and they do not continuously flow through the material and the degradation in performance is much lower.

Based on our lab tests, our products stops adding effective volume when they are half full of suspension oil (by volume). Typically, the total amount of oil inside the air chamber for a service is around 3ml which is a lot less than the volume of carbon we use. Our HIT piston is purposely designed and tested to avoid contamination with oil and grease. We do however recommend not using excessive oil or grease in order to minimise any performance changes over time.

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 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."

PINKBIKE POLE VOIMA

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

PINKBIKE INNOVATION OF THE YEAR 2021 NOMINATION

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."