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Any STW chemists or suspension engineers got some thoughts on these?
For those who don’t know they’re an activated carbon insert that you put in the positive chamber of your fork (like a volume reducer) to make it ride like it has more volume.
The marketing blurb is that because the activated carbon absorbs and releases air from the chamber under compression and expansion it alters the curve of the fork.
It all seems like woo to me?
Are the claims credible? Has anyone seen some independent dyno testing?
There's been quite a few reviews to back up the claims, seems like they could be a good option for large volume air forks like the Zeb and 38 where people struggle to get full travel
Carbon Air (The people behind the tech) produced some pretty graphs a long while ago when in proto stages. The veracity of them I can't tell you but the fork was very much the behaviour of removing tokens, and the shock (I don't know they're going to release a shock one but they did make protos) was more interesting. On a shock it gave the performance of a Megneg type can, but without the increased forces in the latter stroke. Very much best of both worlds in that case.
could be a good option for large volume air forks like the Zeb and 38 where people struggle to get full travel
The first Zeb would have been a prime candidate for it, and I think the new Zeb at 190mm could have benefitted too.
But now I've dropped the travel to 180mm, it's getting full travel and feeling great anyway. I'd still like to try one, but just out of curiosity as I don't really have a problem to fix.
Apologies, I did search for an old thread.
Does anyone know if there’s been any independent dyno testing to show a difference?
I had a brief chat with them at ard rock.
witchcraft.
I'm a curious type and have just put one of these in my fox36 140mm on my HT.
I've only got a couple of rides on it, but the short answer is it appears to do what it says on the tin, but its quite subtle much of the time.
Those that make use of their travel will notice it the most. If you're a tow path trundler or such, you won't notice anything. If you ride anything moderately steep, mid range is definitely more supportive and the fork remains composed better in chunder. Seems like theres a bit more grip. Hitting the 'ramp up wall' is definitely softer too.
Feels a little bit softer off the top - maybe.
These are incremental gains IMO. Putting one of these in doesn't give you coil like performance. Its still and air spring, but a bit nicer.
More graphs from data acquisition to look at
Exactly what Scienceofficer said.
Definitely plausible. Charcoal and derived carbon materials are full of little holes. So when the fork pressurised the air would enter the insert more slowly. So under a hit the pressure would rise sharply then even out a bit more. A bit like having a floating piston with a damper above your main piston. I guess this would do as Science officer says and provide more mid stroke support.
Not got any real experiences but definitely plausible and a rather interesting idea.
“Definitely plausible. Charcoal and derived carbon materials are full of little holes. So when the fork pressurised the air would enter the insert more slowly.”
That isn’t what’s happening here. Their claims are based on adsorption, which is how molecules of a gas can stick to the surface of a solid in much greater density than when moving freely, and as the gas is pressurised more of the molecules attach to the surface of this solid, leaving more space for the other gas molecules. This happens to a tiny degree in any gas spring - but the huge surface area of the carbon insert means adsorption happens to the point that it changes the spring curve.
It’s dynamic enlargement of the positive air spring, with no viscous air damper effects.
Why would I want that when I already need to put two spacers in my fork to stop it bottoming out?
“Why would I want that when I already need to put two spacers in my fork to stop it bottoming out?”
I don’t think you would.
Ah right. Nice, and clever if it works.
I would give it a try if it weren't so expensive. Wonder if you could DIY it with some charcoal?
You absolutely could.
We use granular activated carbon as a sorption media in the course or our business operations. Bought in bulk, its pennies and comes granulated in an appropriate granularity for water or vapour treatment.
If you were of a mind, and had a 3D printer you could do this.
Of course, the margins are huge, but you're also paying for their R&D to determine the optimum mass and configuration.
<p>I was interested in this for a lightweight customer but the insert has a limited lifespan of approx 12 months if I remember correctly. That made it cost prohibitive for him.</p>
I was interested in this for a lightweight customer but the insert has a limited lifespan of approx 12 months if I remember correctly. That made it cost prohibitive for him.
This is the bit I don't get, in industrial processes the carbon is often used to strip out trace amounts of hydrocarbons, so surely the 2-5ml of oil in the air spring is going to knacker these things fairly quickly.
This is the bit I don’t get, in industrial processes the carbon is often used to strip out trace amounts of hydrocarbons, so surely the 2-5ml of oil in the air spring is going to knacker these things fairly quickly.
theres no oil in the air spring- at least in my rockshox, there is a big blob of grease that sits at the bottom of the chanber in my fox, but it seems to stay there
was interested in this for a lightweight customer but the insert has a limited lifespan of approx 12 months if I remember correctly. That made it cost prohibitive for him.
its not a 1 year lifetime
"So far, our inserts have individually spent 100+ riding hours in forks without any noticeable changes to performance. Our earliest prototypes have been in forks for over a year and have maintained their adsorptive properties over time. We are continuing to test and monitor their durability and as we learn more about the long term lifespan we will make more information available."
I've not read anything about a 12 month lfe on these. Are you able to confirm where you found that?
I suppose its about contact. To hydrocarbons. Air piston fluid is fairly viscous, low volume, at the other end of the chamber and generally migrates to the negative, so I presume that mitigates the impact.
I guess you could achieve the same effect (ie larger positive chamber) by making a sealed chamber with flexible hose that screws onto the existing air valve? Or a new chamber that replaces the top cap of the air spring side of the fork? I guess it would have to be positioned in parallel to the fork stanchion so it wouldn't interfere with the bike frame when the handlebars are turned.
Could use a shockpump cabletied to the fork somehow as a proof of concept....
Wonder why nobody has done this? Seems simple enough....
Like a vorsprung secus then
Secus looks like it modifies the negative air spring volume not the positive
I thought I’d read about it on their site a few months ago, and it’s also mentioned in the STW review thread from a couple of months back. Maybe they’ve updated their website?
....or just fit a coil spring and have an even better fork
How many grams of activated carbon are involved here? Lets get real
How many grams of activated carbon are involved here? Lets get real
Total guesstimate from my recollection of handling it during install, I reckon c. 50grams.
hasnt someone already tried the homemade trutune thing
edit it was @dhague
https://singletrackmag.com/forum/topic/trutune-active-carbon-airside-inserts-any-takes/
still can't see any info on then having a limited lifetime
I haven't tried the TruTune, but those of you talking about secondary air springs and floating pistons should check out the Diaz Runt, its essentially a large volume spacer with an IFP and the ability to change the pressure behind the IFP.
It made quite a difference to the feel of my 150mm travel 36. I have been able to run a lower main pressure which makes the fork more supple in the initial stroke and helps it hold up a bit more in the mid stroke (as if you had a large number of volume spacers) but once you reach the usual ramp up stage you get with volume spacers the IFP starts to move making it more linear, the great thing is that you can adjust this pressure so if you still want the ramp up you can have it or if you want it more linear you can have that too.
I have a Runt in a 160mm 36 and a carbonair insert in a 140mm 36.
Its early days, and poor conditions, but they feel different.
It's difficult to express - the runt feels like a really good air spring, but its clearly still air.
The carbonair insert has a more damped, coil-ish feel of composure about it. Sort of like I have a more damped tyre.
I was looking at these at the Ardrock, they had a big clear syringe that was sealed at one end, the difference in pressure with an inset chucked in was very noticeable, they where doing them at a discount so I purchased one for my 150 Fox 36, I’ve only had a couple of rides on it but the fork is a lot smoother off the top, as for snake oil they managed the sell this technology to Audi so there must be something in it.
That might be because they're replacing a lump of very compressible air with a incompressible carbon, so effectively reducing the volume available to compress. But I'm struggling to believe the difference between activated carbon and a rigid sponge block is going to be much
That runt looks interesting. Similar setup to the double chamber in my 66s but without the piece of string.
It's also available for my current Z2s, I wonder if it would help with the issues I have with small bump performance?
I've got both the runt and a trutune, bottom line for me the trutune worked and the runt kind of didn't. I think it's a weight thing. I'm only 11 stone and the runt just made my Pike more harsh on the medium size stuff where as the trutune did the opposite.
Basically if you run a lot of tokens you want the runt, if you run none and aren't getting full travel the trutune will help (or it certainly did for me)
I was looking at these at the Ardrock, they had a big clear syringe that was sealed at one end, the difference in pressure with an inset chucked in was very noticeable, they where doing them at a discount so I purchased one for my 150 Fox 36, I’ve only had a couple of rides on it but the fork is a lot smoother off the top, as for snake oil they managed the sell this technology to Audi so there must be something in it.
I went and chatted with them @ Ard Rock too, with my extra sceptical "I'm an engineer doncha know" hat on...
I left suitably impressed!
If I had a fork that felt like it needed to be more coil like/linear/less ramp up (delete as applicable) then I'd have no qualms about handing them my money. I am happy with the Diaz Runt in my Fox 36's on my eBike as it is (achieves a similar result by a slightly more complicated twin chamber setup at more cost), not that I can even ride a bike right now anyway... But yeah, suitably impressed...
My immediate train of thought went straight onto where else on a bike it could be used more effectively, if the costs weren't prohibitive... I had a good conversation about the possible applications it could have with Matt from Rimpact, put it that way... 🫢
I’ve got both the runt and a trutune, bottom line for me the trutune worked and the runt kind of didn’t.
Due to the nature of it being infinitely adjustable, and both chambers having an effect on each other, the Runt can take some dialling I found... I'm quite a bit heavier than you though, and happiest running 20% sag or less on a fork and having a supremely supportive midstroke, whilst still managing to get full travel under the biggest hits.
The Trutune insert isn't really tuneable as such... Well it is I guess, you could start trimming bits off it. Or you could add a token or two if it has too much effect I suppose. But it's a lot more fit and forget than a Runt is anyway...