The TruTune MTB Air Fork Insert is not a volume spacer. It’s the opposite in fact. The TruTune enlarges a fork’s positive air chamber.

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By ben_haworth

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TruTune MTB Air Fork Insert review – The TARDIS Token

Let’s do this! £120 for fork tokens that are probably printed?!

Could you just drill a load of holes in your current fork tokens?

Rickon they don’t do what fork tokens do, so you could drill tokens, but you’d have to fill them with activated carbon ™

So I ran mine at tweedlove in some really grim slop and came away very happy, amazingly didn’t crash once, even on hammertime! Brand new T9 butcher helped but forks felt really nice, tons of grip and plush without being divey

Been thinking about the physics of these. I have my doubts that it is adsorption, air would have to be adsorbed and desorbed multiple times a second and I just don’t think it’s that fast a process. I couldn’t find any useful literature discussing speed of adsorption, papers tend to concentrate on total volume rather than speed. People seem to be getting some benefit, so I wonder if it is the friction of the air moving in and out of the pores in the activated carbon. This would act like additional damping but more rapid and I think more progressive than oil moving through a nozzle would provide.

These things do seem quite interesting and the science is quite mind boggling. I did assume they were manufactured from “solid” activated carbon but it appears that the “token” is a 3d printed canister containing the activated carbon. Now the science might be funky, but activated carbon doesn’t actually appear that expensive, £106 for 25Kg. Unless there is something techy about the spec of the carbon, it’s does seem kind of pricey. The fact they also have a finite lifespan is a downer too.

I’m struggling even with the initial premise that large negative chambers “cause” greater progressivenessivitude
Surely that’d only be the case if the relative sizes of +ve vs -ve had changed ?

I suppose maybe in a 180/190mm single crown fork there might have to be a trade off between the two and I also suppose that manufacturers might generalise that a typical owner of such a fork might be heavier than Benji and might be expected to ride mighty hard, all of which would mean prioritising -ve over +ve (for the mid- and end-stroke support (err, bro) but also feeling nice in the car-park)

If so, I bet a 40mm DC air fork would piss on the Zeb – are DH forks ever air-sprung these days ?

@scaredypants 99% of the uci dh teams run air forks

I suppose maybe in a 180/190mm single crown fork there might have to be a trade off between the two

Yep, I had a 190mm Zeb v1 and it was impossible to get full travel, way too progressive.

V2 Zeb at 180mm is actually a lot better and I’d only try one of these out of curiosity – I don’t feel driven to by a performance issue IYKWIM.

PS. “Tardis token” is very good Ben

“I have my doubts that it is adsorption, air would have to be adsorbed and desorbed multiple times a second and I just don’t think it’s that fast a process.”

I can’t see why adsorption couldn’t happen this quickly – you’re dealing with a pressurised gas and molecules attaching themselves to the surface of a solid. It’s not like you’re having to push a high viscosity fluid into a porous sponge. Despite the name, adsorption is very different thing to absorption.

I’m not finding much on adsorption timing. The few bits I saw looked slow but with a faster start.

Presumably a shokwhizz (?) would tell you if the pressure was ramping up less quickly.

I wonder if a simple screw on piggy back chamber would work?