Carbon Air Aims to Make Air Suspension More Like Coil - Pond Beaver 2021

Apr 9, 2021
by Seb Stott  

When a press release entered my inbox for a product made from coconut shells and sawdust, which slots into your air spring but somehow has the effect of increasing its volume, I assumed it was a late April Fool's submission. But Carbon Air is the real deal. They've been making products for the air suspension in Audi's A6 and A7 cars since 2017. Now, they're developing their product for mountain bikes.

What is it?

First off it's worth refreshing how conventional volume spacers work and their limitations. Adding spacers increases progressiveness, making it harder to bottom-out for a given amount of sag. But in some applications, it can be hard to use all the travel even with all the volume spacers removed. This is particularly true of long-travel single-crown forks, because the longer the travel, the closer the piston gets towards the top-cap at bottom-out, so the higher the compression ratio. Air spring upgrades which increase the size of the negative chamber - such as RockShox's MegNeg or Vorsprung's Luftkappe, make it harder still to bottom-out because they soften the beginning-stroke far more than the end-stroke, and require more pressure to achieve the same sag.


Put simply, Carbon Air's product does the opposite of a volume spacer. It's made of activated carbon, which is produced by exposing carbon-rich material like sawdust, coconut husks or coal to steam and chemicals, and is used in many industrial applications like hydrogen gas storage (hydrogen likes to leak out of steel tanks) and air filtration. You can think of it like a super-fine foam, with lots of tiny pores within pores in a fractal structure, giving it a surface area of well over a thousand square meters per gram. (For American readers, that's about twenty football fields per quarter-pound).

This enormous surface area allows it to adsorb (yes, adsorb with a "d") more gas molecules than would normally occupy that volume at a given pressure, because they "stick" (adsorb) to the material's surface through something called van der Waals forces. And the higher the pressure, the more air the material adsorbs. According to Carbon Air, this allows one cubic centimeter of their material to take up as much air as two cubic centimeters of empty space. So, counter-intuitively, the more volume of an air spring you fill with activated carbon, the bigger apparent volume it has.


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What does it do?

So Carbon Air can make air suspension less progressive. This could be useful for those who struggle to use all the travel while maintaining appropriate sag. We could stop there, but there's much more to it than that.

While air springs are progressive in the last part of the travel (and this is a good thing, within limits), they are digressive in the first part of the travel. In other words, they have a stiffer spring rate (that's the change in spring force per unit travel) at the start of the travel than the middle. In fact, air springs are often more than three times stiffer off the top than in the middle (older air springs could be over ten times stiffer). It's as if you had a coil spring suited to a 150Kg rider at the start of the travel, then swapped to a spring for a 50Kg rider once you got to the middle. This is what causes air suspension to lack suppleness and traction at the beginning of the travel, while also lacking mid-stroke support.

The RockShox MegNeg significantly reduces the initial spring-rate, but increases bottom-out force.

One solution is to increase the volume of the negative air chamber, which reduces the initial spring rate relative to the mid-travel. But larger negative chambers make it harder to use full travel for a given sag. To ensure most riders can use all the travel with a reasonable amount of sag, mainstream manufacturers want to keep the ratio of positive to negative volume constant. In an ideal world, the positive and negative chambers would be so large the spring curve would be basically linear (but could still be made progressive with volume spacers if desired). The main problem is space. In a single-crown, long-travel fork there basically isn't enough room to do this. The same goes for an air shock which must fit into multiple frames and around water bottles. Apparently, space is a primary constraint in car suspension too, which is why Audi worked with Carbon Air.

This is where activated carbon could be very useful. Whether used in the positive chamber to reduce the bottom-out force when combined with a large negative chamber (e.g. MegNeg or Luftkappe), or in both chambers of a regular air spring.

Activated carbon could be used in both positive and negative chambers to give a more coil-like spring curve.

There's one more potential advantage to Carbon Air's product, but to explain that we'll have to cover a little physics. In an air spring, the stiffness depends on speed. This is because when a gas is compressed it generates heat, and when it expands it takes in heat - this is why your hand pump gets hot when compressing air and your CO2 canister gets cold as the gas expands. This heat generated during compression causes an additional increase in pressure over and above what you'd expect if the gas was at a constant temperature. This causes an increase in the force required to compress the gas quickly (adiabatically) compared to slowly (isothermally), where the heat has time to escape.

This heat dissipates very quickly (with a half-life of about 0.1s, according to Steve Mathews of Vorsprung suspension), so it's most significant in very fast suspension movements. But essentially, air springs are softer in slow compression like cornering and braking, when compared to very high-speed compression like a hard landing. Whether that's a bad thing is debatable, as it can be offset with reduced high-speed damping, but this is another reason why air suspension can lack support under slow movements like braking and cornering, but can be reluctant to use all of its travel on a big impact.

According to Carbon Air, their product absorbs the heat generated during compression and releases it during rebound, keeping the temperature of the gas very consistent. The high surface area and high thermal mass (compared to the gram or so of air in an air spring) of the activated carbon makes it a great heat sink. So, according to its manufacturers, it virtually eliminates the speed-sensitivity of air springs, making them perform even more like a coil while still preserving the lightness and tune-ability of air.

Tobias Ackroyd, Product Development Engineer Carbon Air, also mentioned the possibility of using their product in conjunction with a volume spacer if you wanted to maintain the same progressiveness but still offer the benefit of reduced speed-sensitivity.

I did wonder if the material takes time to adsorb air during compression, which could introduce another speed-sensitive effect as the insert would act like a volume spacer until the air had time to "soak in" to the material. I asked John Coakley, CTO of Carbon Air, "Can it adsorb air fast enough to keep up with the fastest suspension movements, which are somewhere in the region of 10Hz [ten cycles per second]?" Apparently, activated carbon can store and release air so fast it's effectively instantaneous as far as suspension is concerned: "It's used in loudspeakers where you can see adsorption and desorbtion [the reverse of adsorbtion] in these materials up to 400Hz," John told me, "so for this application, you're not going to see any speed-sensitive effects."

The future

Carbon Air is discussing with suspension manufacturers the possibility of integrating their product into future air spring designs. For obvious reasons, they were not keen to share any more details on that. As for whether it will be available aftermarket to effectively increase the positive and/or negative volume of existing air springs, that may depend on the result of those discussions.

Personally, I'm a a big fan of negative volume upgrades like the RockShox MegNeg and Vorsprung Luftkappe, but in some applications (frames with progressive leverage curves and long travel forks, respectively) they can make the spring too progressive. An aftermarket option which makes it possible to make use of these upgrades without excessive end-stroke force could be a step forward for air suspension.



Pond Beaver 2021





238 Comments

  • 328 2
 Damn, people are being negative already. This is really fucking cool!!!
  • 174 2
 I agree. Seems like one of those relatively simple idea that makes you wonder why it hadn't been tried before. It looks like Audi had an exclusivity contract on it that's now expired, which is why they're working on branching out into other areas, like mountain biking.
  • 12 11
 @mikekazimer: I thought this had been done before, could have sworn we saw something from an italian company (formula ?) a year or two ago.
  • 22 1
 @DGWW: formula was more like « soft » token I believe
  • 10 0
 Just look at the Force and Stiffness charts for the carbon inserts... Those charts are linear scale not log(x), so if true, you could actually feel the difference.
  • 21 0
 Agree, this is pretty neat. A volume spacer that does the opposite of a volume spacer. The anti-volume spacer? Science!
  • 3 0
 @DGWW: RST did something like this in the late 90's.
  • 11 0
 @DGWW: Forumla NEO POS - Just soft spacers that crush a little as the pressure ramps up. Works, but not to the same degree it seems this would.

www.pinkbike.com/news/review-formulas-neopos-volume-spacer.html
  • 3 4
 I think that negativity comes from expected price. I believe this can work, I have been using Neopos and it's awesome, especially for the price. This should be much better, but I can already imagine the proce tag ...
  • 34 1
 It's because it has science to back it up - so it is immediately disregarded down here....
  • 15 0
 Activated carbon has lots of uses like air filtration. Your fork air will come out cleaner than when it was pumped in!
  • 8 2
 @mikekazimer: "which is why they're working on branching out into other areas, like mountain biking."I think it's more because they know that MTB market is crazy hot and people are ready to spend fortunes in bikes and PARTS!
  • 7 0
 I automatically assumed that this was a pun about "negative" progression, I have apparently spent too much time in the Pinkbike comments.
  • 9 1
 @skeeple: you can keep your science and your microchip zombie vaccines, and Ill keep my single speed freedumb spreader!
  • 2 0
 Negative air
  • 3 0
 I really want to try this... what an interesting idea
  • 12 19
flag TW80 (Apr 9, 2021 at 15:28) (Below Threshold)
 Hmmmm, wow. WTF was this article about? Could someone (seriously) explain this. and while you are at it, explain progressiveness etc, oh and do it like I'm 5! Please... I say this cause A) I pressurize my shock & fork to manufacture recommended specs based on my weight, B) ride, C) if I ever think there is an issue, I recheck and re-ride for a year, then re-tune. Yeah, I bottom out on big hits, chatter the F-ck outta myself on rocky shit and laugh the whole way down the mountain cause I remember the days of no suspension, then a tiny bit-O suspension to where we are today! Riding freakin bad ass bikes that are essentially an engineless dirt bike! Thx.
  • 5 0
 @audric: Fact. Mountainbikers are just preconditioned to find justification in everything they are overpaying, which is just about everything that we buy.
  • 14 0
 @TW80: I guess since nobody has tried so far, I'll give it a go.

progressiveness is what happens when the fork goes through it's travel. Lets say you have an un-squished fork with 80 psi in it, this is going to feel pretty soft in the initial part of the travel when you press down on the bars. Now let's say you land a jump and your fork sinks all the way to the end of it's travel. You still have the same amount of air in your fork, but now your fork is shorter, and the air has less space to be in. the same amount of stuff in a smaller space results in an increase in pressure, there's now maybe 150psi in your fork. These aren't exact numbers but I'm sure you get the idea.
Just picture it like trying to pop a gym ball by hugging it, it's easy to press it to start with, but the harder you squeeze it the higher the air pressure inside it gets and therefore harder to squeeze it further.

This article is about a material that can absorb more air than just a straight air chamber. I think this means that the air spring will feel like it's bigger and softer than it actually is, resulting in a softer ride.

I hope this helps
  • 1 0
 what you need is to stop calling the truth negativity. you can't ride a bike without a bike.
  • 1 0
 PBers might spring up after some good reviews.
  • 13 0
 @Powderface: If a volume spacer and an anti-volume spacer collide, the enduro rays and bro-particles will vaporize any Yeti in range
  • 1 0
 Agree. Will buy for my Zeb as soon as it's available.
  • 1 0
 @islandforlife: That is not the concept at work here. It's not a squishy volume spacer, its the opposite. It makes the effective volume larger, not smaller.
  • 1 0
 @billschonman: I was referring to what the Forumla NEO POS spacers do, not the carbon ones.

NEO POS, are soft and squish and so the more ramp and pressure applied, the more the squish to allow for a slower decrease in volume. Yes, different from what these carbon spacers do.
  • 332 38
 After Trump, I don’t trust anything that wants to put carbon in the air and make things less progressive.
  • 7 0
 @suspended-flesh: it took me so long to realize what that was. Turning the phone sideways did it!
  • 266 1
 I'd don't really understand it, and therefore I hate it, but I still want it, even though I probably don't really need it.
  • 3 0
 I'm with you on this.
  • 11 1
 This is possibly the most brilliant post I've ever read.
  • 5 0
 very smart Sir... I have a cellar full of those things..
  • 86 0
 I just want to say that the main reason this is so interesting is because it was explained so well. Excellent writing explaining pretty complex stuff in a way that can be consumed and understood (if only at a high level). Kudos.
  • 8 1
 Zactly. I've learned more about how our bikes work in the couple months since Seb joined PB than in all my 10+ years in this obsession. I've also just found out why I'm having a hard time dialling in an air shock.
  • 8 0
 Completely agree.
I started reading the article sceptically, then relaxed when it became apparent Seb knew what he was talking about so well he could explain it without a reliance on hand waving and jargon.
I genuinely never expected an (accurate) straightforward disambiguation for adiabatic and isothermic on Pinkbike. Top stuff @seb-stott and PB for bringing him onboard.
  • 6 0
 Thanks very much! Glad it makes sense.
  • 2 0
 @nhlevi: Agreed, @seb-stott and @dan-roberts have been awesome additions to the staff. Makes a world of difference to write from real technical understanding vs what is frequently gut, guessing, pseudo-science and repetition of marketing materials (which are usually already distorted by non-technical marketing teams).
  • 35 2
 "For you American readers..."

Hahah. Literally have to reference everything to football fields. Or BigMacs.

It's a lost cause. If only we could just be metric like the REST OF THE WORLD....
  • 3 1
 I wonder how many McRoyals high is 29” in say.... Spain?
  • 30 3
 Can I take this out and use it to filter the pond water for a mid-ride drink? I ride a Capra, no water bottle :shrug: ...or maybe it could clean the air as the suspension cycles. Wink
  • 5 0
 the suspension is the pump the insert is the filter
  • 3 1
 dammit, just came to me. Should've posted: "Do they charge extra for a Hepa filter to go in the damper?"
  • 26 1
 Carbon Air. Seems Legit. How do I inject it into my tires?
  • 7 0
 lighter than regular air! get some today for 12 monthly payments of 15.99$ !
  • 8 0
 Actually, tires are doing similar actions as shocks, so why why couldn't the inside of a tire be coated with this, would it provide similar benefits?
  • 4 0
 @On3-kn0WN: hucknorris with carbon inserts!
  • 5 0
 @mark4444: actually that might work.
  • 3 0
 @On3-kn0WN: thats an interesting idea. I wonder how it would respond to sealant and deformation
  • 1 0
 @On3-kn0WN: Most people struggle with too-soft tires I think, not too hard ones. You also don’t compress the tire volume that much compared to a suspension element.
  • 2 0
 @On3-kn0WN: one of the benefits of inserts is they act as a volume spacer. I’m not sure why you’d want effectively more air volume in the tire. A tire is nice to be soft off the top for bumps and grip, then be hard to bottom out. Progressive is pretty much better in every way
  • 1 0
 @mtmc99: Obviously couldn't run the activated carbon in contact with sealant, but could be sealed inside a low pressure inner tube smaller than the tire, with air and sealant in between the tube and tire through a second inflation valve. This way you could even tune how progressive the tire compression is by increasing or decreasing the air volume in the carbon-filled tube. This could be very interesting for hard-tails or rigid bikes, like most fatbikes.
  • 1 0
 @JediJiJi: Too progressive and tires get bouncy, just like air suspension inadequately dampened. The more the tires bounce, the more the suspension has to work. If you have enough volume to avoid rim strikes (which is the real purpose if inserts) it's better to be less progressive, not more. Mercedes made wheels for F1 cars that had hollow spokes to increase the air volume to decrease pressure variation for better suspension control. My only question about the use of activated carbon in tires is whether it would increase rolling resistance - I suspect it would, but might be offset by being able to use higher pressure without bouncing.
  • 22 1
 .... Guess it's Springtime
  • 15 1
 Yeah, coil spring time.
  • 4 4
 Hear that spring rattle?
  • 2 0
 @theteaser: sounds like your for needs a rebuild buddy
  • 1 3
 Nope. Air sprung. All quiet here.
  • 2 0
 @theteaser: My FOX 40s are silent after I made this spring keeper and did away with the travel spacers

www.pinkbike.com/photo/20421092
  • 1 0
 "Spring is in the air" is what I should have said instead (damn! Missed opportunity).
  • 16 0
 What about lube oil coating/soaking the carbon- will that negate the effectiveness?

These are going to live inside a lightly oiled environment- tokens are always oily when removing them after use.
  • 3 0
 Great question. And even without oil, does the effectiveness of the carbon foam degrade over time? How many of these things do I expect to have to swap and throw in the trash in 5 years?
  • 2 0
 It would be interesting to know if they had to solve this in the original car application
  • 32 16
 Unless it somehow removes the extra seals required for an air spring, it will not match the small bump sensitivity of coil.
  • 67 5
 Possibly, but it's also not going to weigh nearly as much as a steel spring.
  • 31 21
 @mikekazimer: the other big benefit of coil is never having to check your pressure.
  • 92 5
 @adrennan, and the negative is that you can't fine tune the spring rate nearly as easily as you can with air. There are pros and cons to both designs.
  • 11 0
 @adrennan: They're talking about the spring curve. They didn't claim to do any of these things.
  • 10 1
 @adrennan: but it sucks when you riding weight fluctuate.
  • 14 1
 @mikekazimer: I no doubt acknowledge pros and cons; I am more just salty that more companies arent making a coil fork that is amazing. (and I am bored at work on a friday)
  • 8 3
 @adrennan: I'm very much enjoying the 5 people who think you have to check the air pressure of a coil fork.
  • 5 0
 @ybsurf: it's just a different way of thinking about it. I was riding air for years, tweaking suspension before each ride. Now with coil the last couple of years, you adapt to the suspension a bit more.
  • 6 0
 @BenPea: some coil forks have an air assist like old Marzocchi 66's. Maybe they are riding 10yr old forks? I have no idea if there is a current OE coil fork with this.
  • 6 0
 I like how this shows the downside of an air spring in the beginning of the stroke. Typical articles always say air travel is "even more perfect than before" as if there aren't any downsides at all.

If this improves the beginning of the air stroke and coils get hydraulic bottom out, then maybe all forks will have close to ideal progression.

Then the coil/air debate will mainly about weight and sensitivity.
  • 2 0
 @MattyBoyR6: I knew this was going to come up the millisecond after I submitted. I've even got a 55 where this is the case. But I also have a Lyrik coil that backs up what he said to perfection, and that's where I'm coming from.
  • 3 0
 @adrennan: yeah man, thats the reason I bought the Smaspot because no one makes SC 180mm coil forks for 29"
  • 1 0
 @BenPea: ha ha yeah man I get it. I only knew because I had one of those 66's. I set it and forgot it and never had to mess with the air. Coil is the jam.
My current air is set in my house at 74 deg F (23.3C) but current outside temps are 90 F (32.2C) but soon to be in the 100's. If I ride in the morning it will be 60 F and all of those temps will definitely change the feel. Ugh then going up north this summer to escape the heat where I'll gain 5-6000 (1828m) feet will also affect the PSI.
  • 1 0
 @MattyBoyR6: and maybe its just the dvo stuff I have now but I notice a difference in spring feel often. I just want my bike to feel the same every time I pick it up to go ride. Maybe give the tires a squeeze to make sure they are still good.
  • 1 0
 @Serpentras: 180mm zebs are pretty coil like in the progression department.
  • 5 0
 @MattyBoyR6: I can't ride for shit below about 5°c and it's definitely due to the air shock and not me being a pansy.
  • 13 0
 To the commenters doubting these claims: It is 100% legit tech. Porsche and Audi have been using something thats similar in function for years in their air shocks. Apparently it works just fine even under heavy usage and very dynamic applications.
  • 1 4
 I’m not a doubter but I am a skeptic, the applications it is use in both Porsche and Audi, it is hardly the most remarkable aspect of the suspension.
The A7 Audi for example has fully automated ride height and damper control.
And Porsche, well let’s just remind ourselves of the Oxides of nitrogen debacle that saw the head of Porsche engines quit after getting caught.
Blindly believing slick marketing talk is what has filled the bicycle industry with overpriced rubbish.
  • 17 1
 they better ramp up production on these things...
  • 14 0
 I used to design Vacuum Swing Adsobtion Oxygen Generators for commercial and military use. This is really trick technology and a great application for it.
  • 3 1
 You too?!?! My vacuum swing adsorbtion oxygen generators were primarily for military use though, with some commercial applications. At first I thought we had a lot in common, but really not much at all the more I think about it.
  • 11 0
 What a good idea, had no clue that this is already being used in automotive! Love technical articles like this. There is waaaay too much snake-oil and half-legit claims about mechanics and physics in mountainbike world.
  • 10 0
 I had a really scary over shoot to flat landing the other day just getting back on my fs bike and sending some stuff I have avoided this winter on the hardtail. I landed fork heavy, which is my calling card, but did not bottom out (2nd ride on some newish settings probably oversprung). The discussion of the air spring being stiffer on fast high energy motions is interesting and may have been what saved my ass from a super hard fork bottom out. This product seems super cool and I am jamming my air springs full of Kingston briquettes as soon as I get done typing.
  • 13 0
 All I hear is heavy breathing from the Luffkappe guy...
  • 9 0
 this is truly interesting. As a habitual suspension tinkerer I really hope they do come out with an aftermarket option...that's reasonably priced.
  • 9 0
 That is pretty darn cool. Hope it still retains it's properties in an oil rich environment.
  • 1 0
 Depending on the grade (pore size), activated carbon adsorbs organics like oils quite readily. Looking at the picture in the article it appears they've installed some type of filter or screen on either end. Perhaps they'll need to encase or seal the rest of the body with another material as well.
  • 18 11
 This is one of those things that costs them like 25 cents to make, and then they'll charge like 100 bucks for it cause it says 'carbon' in the name.
  • 57 1
 Right because the only costs involved in a product is making it. There aren't any other ones.
  • 8 0
 Go down to local pet store, buy activated aquarium charcoal, replace volume spacers with similar volume charcoal. Sounds easy enough..
  • 4 1
 Carbon is the new GOLD
  • 4 3
 @DylanH93: I’m just going to pack an oil resistant, closed-cell foam (like a Croc) cylinder into the air chamber and see what happens. I’ll cut them at different lengths and call them Forkbucks. Zero research, but the production cost vs. potential gain is through the roof
  • 3 0
 Can we get a big feature comparison going with these, a DSD Runt, Vorsprung Secus, Coil conversion, tokens, and stock fork? @mikekazimer . Maybe with some datalogging and timed runs to keep the bro science in check? I think that would be fascinating ...
  • 13 11
 Instead of going to great lengths to make an air spring feel like a coil, why would you not just buy a coil fork/conversion? Once this is added in then the small increase in weight is even smaller, plus you don't have all the seals and stiction associated with an air spring. Seems like someone trying really hard to justify their time at university....
  • 8 0
 Because they dont make springs stiff (lbs/in) enough for my big ass Frown

Totally get your point though. Why go through such great lengths to get a coil like feel when a coil exist.

An airspring will always allow for fine tuning that just isnt possible with coil.
  • 3 0
 I just wish there were at least a few companies where they were making their flagship/ all the tech models with a coil.
  • 9 0
 Most coil models are 350-450 grams heavier than stock. I have one on my bike and love it but I understand why people don't want a 36.5 pound bike (with light tires and carbon frame).
  • 3 1
 Hows about carbon coil springs and shock bodies?
  • 4 1
 Spending my time on in university working on such carbons I can tell you that this application is very very small compared to the tons of it going into other processes each day Big Grin If there weren't people going to spend time at university we'd be all riding bikes with wooden wagen wheels today Big Grin
  • 2 0
 wellp coil conversion kits make your fork extra heavy. My Smashpot adds 600g to my Lyrik. Other then that, it is brilliant.
  • 5 0
 Marzocchi's old low-pressure air-assisted coil spring worked well on their 55 RC3 Ti. (it was the oil leakage that was a problem...) It would be cool to see more manufacturers offer Ti-sprung coil forks with 3 or 4 spring rate choices, with a similar low-psi air system to fine tune the spring rate.
  • 3 0
 @Serpentras: Agreed. I have coil front/rear now and it feels great... but man it's heavy. I wish I didn't have to go that route. I hear a lot of people saying "you don't even feel the weight" when they're talking about the benefits of coil. I call BS - it's extremely apparent. I'm a weirdo who enjoys the ups as much as the downs so I may have to back off the down end of the spectrum just a little.
  • 2 0
 @jpat22: I wonder how much of that depends on rider weight. I am over 200 pounds so the percent change to the total weight is less adding a coil. While kaz is a skinny lad so it's a bigger percent change in the total rider+bike system.
  • 3 3
 @Serpentras: 600g?! You mean that your Lyrik weighs as much or more than a Boxxer WC? Basically just 200g short of 2007 Marzocchi 66RC2X with TWO coil springs!

I like the idea of the coil conversion but I don't understand why would someone want to make coil work more like air... when most to make air feel like coil... I respect Vosrprung but... this is a bit confusing. In the old days coil fork was 300-350g heavier than it's air version (like first gen Lyrik), and if you found a titanium spring, it would go down to 200-250g difference.
  • 1 0
 @justwaki:
Push ACS-3 added 275g to my Fox 36. and 250g to a Pike.
I saw posted weights/photos where a Vorsprung smash added abuot 400g. Other posts backed up that Smash adds a little more weight, I think because their spring is longer to make it compatible between brands. Anyway just wanted to post some real world weights for anyone considering the conversion. Besides the improved feel, I was surprised how much I enjoyed the "never have to check or fill your fork again or worry about temp or altitude.". It seems like my pressure would always be prretty good until I didn't check it for a few rides and hten all of a sudden 30 minutes from the car would realize it had lost some pressure. But I still wouudln't have made the switch but for the improved feel.
  • 2 0
 @chrod: avalanche has a hybrid air/coil option. Sounded similair
  • 7 0
 @justwaki: It's less crazy than it sounds. The first part of the increase in the delta there comes from the fact that air springs have gotten significantly lighter than they used to be. Fox air springs for example used to have two negative coil springs in them, which weren't anywhere near as light as their current air negative systems, and some air springs back in the day had steel shafts. The second part of the change comes about from the fact that air sprung forks typically use shorter stanchions than equivalent travel coil sprung forks used to, which necessitates the use of a cartridge & longer spring. You can cram a spring into the short stanchion, but you're much more limited in the spring rates and travel which you can run before the spring takes a permanent set.

To give a standard of comparison, a 29" Lyrik or 36 with Smashpot is around 2400-2500g for most spring rates. A 66RC2X was 3160g (www.bikeradar.com/reviews/components/forks/suspension-forks/marzocchi-66-rc2x-review) in 26".
  • 2 3
 @VorsprungSuspension: I stand corrected. 2.5kg for a fork is more than acceptable. Never had issues with carrying around Lyrik 2007 Uturn which at least had a real CSU.
  • 2 0
 @preston67: well I did not get the asc3 because tow things. Air chamber and max travel is less then 180mm
With the smashpot I have no air chamber and can do the same thing with just a hydraulic knob on the power like the rebound knob only for buttom out control. And off 180mm of travel.
  • 1 0
 @Grosey: Öhlins do the same on the 36m2 - you can swap between coil and air. I'm currently on cÖils and liking them.
  • 1 0
 @adrennan: good point, I’m lanky too
  • 1 1
 @lefthandohvhater:

Yea I understand too; they hate bikes.
  • 4 0
 This is awesome. I can't wait till Steve from vorsprung gets his hands on one. I would love to hear him talk about it. Does anyone know his pinkbike handle?
  • 3 0
 Isn't it just @vorsprungsuspension (look at the old Tuesday tune articles if not)?

Also, LH OHV is rad, ya' hater
  • 1 0
 @sspiff: it would be more rad if they let dirt bikes back on it. Damn hippies...
  • 1 0
 @sspiff: Hehe its alright. Just a bit over rated IMO
  • 1 0
 @lefthandohvhater: Next to every other trail system in Boulder though.... It's the only thing I'd drive up there (from Golden) for!
  • 7 0
 @lefthandohvhater: without thorough investigation I can't say 100% for sure, but on cursory consideration this concept appears to be legit and more or less as-described (though I'm not yet completely sold on the reduction in velocity sensitivity, but haven't tested or calculated that so far, so willing to take their word for it for the moment). It basically lets you increase effective air volume without increasing actual air volume, in other words you could theoretically get say 100cc of actual air volume to behave as though it's 200cc of air. That alone doesn't just automatically solve every issue with air springs on its own, but it is a very cool idea that could definitely stand to open up new possibilities to improve things in forks in particular.
  • 1 0
 I can't imagine how slow you'd need to compress your suspension for isothermal compression. And if it's desirable, why haven't we seen fins on air springs?
  • 6 0
 OOOOH SCIIEEENCCEEEE!!! In my fork! Science in my fork!
  • 2 0
 The point that there isn't enough room in a long travel single crown fork for the volumes of the chambers to be large enough to make it feel similar to a coil is not very valid. There is indeed enough room in there to do it, just nobody has done it yet. Using a 38mm stanchion fork at 180mm travel for example there is absolutely enough room in there for an airspring to have an almost identical curve to a coil spring, the problem isn't the space, its actually the shock pumps. You need upwards of 600 psi up to about 900 psi to do it but you can get a perfectly linear spring curve with it. You can still fit a good medium in there with an airspring that goes up to 300psi for a over 200lbs rider weight and varies from a coil spring force per displacement by +/- 3-4 lbs through most of the stroke until end ramp up starts at about 140mm travel if its a 180mm fork and at bottom out you would get about 1x equivalent spring rate as extra bottom out force. A rate equivalent to a 40lbs/inch spring would provide 40 lbs extra force at bottom out over a coil.
  • 2 0
 Wouldn’t air spring seal friction go way up if forks did this?
  • 1 0
 I sure hope people remember to let the air out of their air spring before removing the top cap. Would be quite a bit more violent than at current pressures.
  • 4 0
 @sdurant12: Yes and no. If you use the same amount of "static" squeeze on the seal then yes, you would have more friction from the seal. Seals are dynamic and seal with more force the higher the pressure they are sealing as that pressure deforms the seal. If you use less "static" squeeze on the seal to begin with then you might end up with only a small amount friction more at those higher pressures. There are also alternative styles of seals that can be used in place of orings to reduce friction.
  • 2 0
 @MaplePanda: dont worry about that new leak in the roof!
  • 1 0
 @naturaltalent: got it. I would have thought you’d need more static squeeze so that the air couldn’t squeeze by. But I guess seals are designed in a way that increased air pressure forces the seal to seal more tightly? Like a tubeless tire.

I’d always imagined that the air was trying to squeeze through past the seals. But I guess you can use the difference in air pressure between each side of the seal to your advantage. Neat. Thanks for the insight
  • 1 0
 @naturaltalent: any idea what some of the challenges might be to higher air pressures? I’d imagine there’s something? Is it just a safety issue? That’s the only other thing that comes to mind for me

It can’t be that hard to make a 900 psi shock pump, can it? Shocks and forks usually come with a shock pump anyways so why not ship a 900 psi shock pump and use this design?
  • 2 0
 @sdurant12: bang on about seals there. The challenges to higher pressures is convincing people that their fork works a heck of a lot better but weighs a few grams more, as to do it requires a twin tube setup for the air spring. The safety factor of the stanchion tube is reduced with higher pressure for the same wall thickness, but with a thicker tube it can still remain well within an acceptable limit. Saftey factor of about 3-3.5 running at the higher pressures on a 38mm tube, depending on wall thickness. Thats on the low side for pressure vessels, ideally a safety factor of at least 6 or higher would be better, this is where the extra weight would come from. Bigger range pressure gauge and smaller diameter tube on the shock pump, you will be pumping for a good while to fill the fork too. The shock pumps that exist right now get quite hard to compress near 300 psi, RS makes a 600psi variant, 900 psi would move a very small volume of air, it could be a 15 min process just to pump the fork up from zero at those pressures. At the weight of an airspring that perfectly mimics a coil, its simpler, easier, and safer to just use a coil spring. Don't have to worry about seals, less friction, more consistent.
  • 2 0
 There's no way the chunk of carbon could be isolated from the oil, and since they're both non-polar, the oil will get pushed in (with the air) over time. I guess the pore size could be small enough to prevent big ol oil molecules from getting in, but the outer surface will still be coated with oil, preventing the air from getting past. . .Not trying to hate, but my chemistry teacher brain asks what others have said earlier - "How does the thing work with oil on the surface?".
Maybe it simply does, but . . .I'm skeptical
  • 1 0
 We need them to work with Vorsprung to make a piston that uses this to increase the effective negative chamber volume without eating into the positive chamber volume. That would basically be a Secus that would fit entirely inside the stanchion. Then you’d ALSO have space to run a volume spacer of this stuff in the positive chamber of you still wanted less progression.

I have a Luftkappe in a 150mm Pike that could go to 160mm except at that point it’s too progressive (with zero spacers) to ever get full travel.
  • 1 0
 Here ya go boys: www.amazon.com/AQUAPAPA-Activated-Charcoal-Pellets-Aquarium/dp/B01F1QZTQC/ref=sr_1_25?dchild=1&keywords=activated+charcoal&qid=1617995894&sr=8-25

Start packing your air cavities!

My wife also appreciates it when take charcoal to adsorb the gas.
  • 1 0
 If not ridiculously priced I’d give these a try as I agree the issue with single crown air forks is not enough volume to work with not the other way around where they’re stuffed with solid tokens. Seems the trend is finally catching on where the new 38 is designed to have a lower compression ratio and most testers in the Zeb running zero tokens where in the past everyone was using 3+ tokens and I could never understand how they were doing that (it felt horrible). These look pretty promising.
  • 1 0
 very cool tech innovation. my concern would be dust or breakdown of the carbon due to vibration and impacts over time and that carbon dust wearing seals and sealing surfaces. Any comments from carbon air regarding durability of their units?
  • 1 0
 Thanks for the decent write-up @seb-stott,
I was waiting to pounce re the adsorb vs absorb.

Computer modern typeface on that figure, got a link to that document? Looks legit.

Also: probably the first product launch I've ever seen that shows graphs with actual units, and it's hated... This is why we can't have nice things.
  • 1 0
 Just remembered the cascade links.
  • 2 0
 I actually like the way a vorsprung makes it harder to bottom out, it feels super supportive and not harsh, much like a coil. As compared to all stock air forks without upgrades, which all wallow.
  • 1 0
 I really hope to see this come out as standard equipment in the suspension world. It would be amazing to have more of all the positive performance traits we look for in air suspension come from something so simple in its design.
  • 1 0
 Took a while to sink in what this is doing, basically increasing the (molecular) air capacity of the stanchion.

This can also be done with longer stanchions of course - I've tried running my Lyrik at 140mm and prefer it to Pike at 140mm - I guessed because the travel stays in better behaved area of air spring.
  • 2 1
 So, it nearly makes an air suspension feel like coil and was developed for a car manufacturer. Maybe their R&D team are looking for adjacancies to sell their product too and have the marketing team on it now...

Over to Seb, what's in your WRC car.

www.wrc.com/en/news/news-archive/wrc/ogier-restart-in-doubt
www.wrc.com/images/redaktion/Season-2020-NEWS/WRC/6_June/020620_Five-biggest-tech-breakthroughs-05_dff57_frz_1400x788.jpg

If this was that good then WRC would be all over it.

Sticking with my old school coil spring thanks.
Its 200g heavier, makes my bike 1% stiffer, is 2% less adjustable on the spring rate, but 5% better on the trail. Never suffers from air leaks, ambient temperature shifts or sticky seals.
  • 1 0
 They are basically using the principle that an air molecule(primarily ~78% N2 or ~ 20% O2) to activated carbon 'bond' or association(more of these made by more pressure) takes up less space than a nitrogen or oxygen molecule just hanging out with another nitrogen or oxygen molecule. Like folding up your clothes and putting them into a drawer instead of a big unorganized heap on the floor. Basically there is a lot of space between air molecules and the activated charcoal(sorry carbon) along with pressure allows the air molecules to fall in line like good little soldiers. And next up we will need to fill our shocks with all nitrogen(helium would be more fun) to maximize this benefit.
  • 1 0
 Very cool idea. However, as a chemical engineer, I question whether the characteristic time of suspension movement (fractions of a second) is compatible with the rate of heat and mass transfer required. The curves are very impressive, but do not address this issue.
  • 1 0
 This stuff is so cool. As much as cyclists find themselves at odds with motorists, it's funny to note how much MTB tech is carried over from sunk R&D costs in the auto sector. This one has an additional layer of irony in that lots of research in activated carbon has been done in the context of green tech with the purpose of capturing CO2. The web is nice and tangled.
  • 1 0
 It would be a rare rider indeed. Who just brought a big 38mm fork, an cant use all the travel. But who also refuses to let any air out to increase sag/ and make the fork more supple.

I run a RUNT, and it allows u to use a lower then normal main chamber air pressure for a supple beginning stroke. And the second chambers high pressure side, creates a magic supportive mid stroke platform to ride off. Interesting tech, good article!
  • 1 0
 So its the aDsorption of even more gas molecules to the greatly increased surface area that is the key to this thing doing what it does.

Seeing as Fox advise a 'splash' of Fox Gold in my forks air chamber:

What happens as that surface area becomes contaminated with lubricating fork oils? Will the adsorption rates diminish and change dramatically, in effect just turning into a regular old 'token'

Will it need to be decontaminated regularly for maximal operation.
[Reply]
  • 1 0
 This is pretty cool application of technology. I don't think it's going to be great for someone to just pick up a cylinder of the stuff and fire it into their bike as an aftermarket add on... (maybe if they come up with pre-made kits for the most popular forks?), but if it's integrated into forks at the OEM level- they might just find a very nice little market for themselves, and make air suspension better for all of us. I wish them luck!
  • 1 0
 Clever tech and a writer up to the task of explaining it. The speed-dependent temperature effect was a good question. Great work Seb. Activated carbon is cheap stuff. Hoping these things are reasonably priced, but that's usually not the case for new cycling tech.
  • 1 0
 So they design a part to enhance the negative aspect of a coil spring? The big advantage of a coil is the super supple suspension in the first part of the travel, backed up by a strong mid support, with the disadvantage being the lack of ramp up (hence the smashpot was designed).
  • 1 0
 Would anyone be able to explain why air forks are digressive at the beginning of their travel rather than progressive the whole way through? That must be because of damping properties, right? I don't see how it could be a property inherent to a pure air spring.
  • 4 0
 It's been a while since some cool product came out for suspensions
  • 2 0
 Very cool product for lighter people like myself. Also great explanation of the physics behind this stuff by Seb. Keep it up.
  • 4 0
 my coil feels just like a coil !
  • 2 0
 I was also thinking you could just buy a coil.
  • 1 0
 Oh! You could also put this stuff in the lowers to help with the non-tunable air spring you get from air trapped in the lowers. I wonder how it does when it get covered in oil?
  • 3 0
 Been tossing Kingsford Briquettes in my fork for years now! Now that the secret's out, I'm gonna lose all my KOM's.
  • 2 0
 Why don’t more companies focus on making coil a bit lighter, most spring weight options and easy to change springs? Coil suspension with no downsides.
  • 2 2
 All this science and technology to chase an inferior spring medium....air will never be as good as coil and I will never ride air springs again. Damn the extra weight, I couldn't care less about the extra weight because coil springs are superior in every way. The "fine tuning your air spring is easier" is nonsense as that happens ONCE with a coil and your set unless you suddenly gain or lose a bunch of weight.
  • 2 2
 I'm not a very smart man. The description about the technology was beyond my comprehension. What I'm wondering is, instead of making air feel like coil why not just run a coil spring? Back many years ago I had a coil 40 and a coil lyrik. I then switched to a 2018 boxxer WC which was a downgrade to the 2012 40 it replaced. Same experience when I bought a new bike that came with a 2016 lyrik. The coil version I had was a 2011 and was much better.
  • 1 0
 Fear not, there's still Boxxers out there under the fastest with springs in them.
  • 2 0
 Wonder if they'll do a chamois insert too? Never a good idea to follow me down a trail after beer and pizza night. Activated carbon filtration might be just the ticket.
  • 1 0
 Forks have some a long way since Judy's and Z1's were the party. I def appreciate this, and all that advancements to what still just a telescoping fork. Also very thankful it's not just a new axle size.
  • 1 0
 Looks like they are focusing on Rockshox Pike and Deluxe but also have prototypes for Boxxer and Fox 36.

carbonair.co.uk/2021/03/29/carbon-air-products-in-bike-air-suspensions-and-shocks
  • 1 0
 This rings true. Despite running way lower than recommended air and no tokens my 180 Yari never uses full travel. Not that I mind much as my bars are too low for my liking anyway.
  • 3 0
 How much is that gonna cost?
  • 2 2
 Looks like this:
www.deaneasy.it/en/shop-deaneasy/abs-fork-tune-comfort-and-grip
I think I've seen other versions as well.
I'm interested in trying it, but I'm a kook.
  • 4 0
 Those are just a soft version of a volume spacer. this product literally does the exact opposite of that.
  • 1 1
 @mixmastamikal: fair enough that they are technically different, but the goal of both seems to be the same:

From Formula Neopos (basically the same as deaneasy):
"Neopos makes it possible to make the air fork’s progression curve more linear..."

From above:
"So Carbon Air can make air suspension less progressive..."
and for good measure, "You can think of it like a super-fine foam"

Neopos/Deaneasy acheives this through an easy to imagine a change in density:
air-to-spacer volume ratio in the chamber changes as the foam is compressed the stroke,
like when you squeeze a foam stress ball.

Carbon Air claims that van der Waals forces allow their material
to "adsorb" more air as the pressure increases,
such that "the more volume of an air spring you fill with
activated carbon, the bigger apparent volume it has."

So, essentially, there is x amount of air in chamber at start of stroke,
and as the Carbon Air is compressed, additional air volume is 'created'
during collection of air molecules in a film on the surface of the material.

But, of course, this air chamber is sealed by necessity.
So if air was actually being "created", it would be be pulling from outside the sealed chamber,
which would be bad.
So, I think it might be accurate to say the Carbon Air material is *also* increasing in density,
but instead of expelling air like a foam, it is collecting ("adsorbing") air,
using it to make the CarbonAir material, by way of SCIENCE, more dense.

If my interpretation of CarbonAir's performance is correct, (a big if, I know)
both products would be trying to regulate compression of the air by adding a variable density
material to the chamber, or to put it another way, by displacing air during the course of the stroke.

If the CarbonAir compression process does actually reduce heat,
that would mean the Neopos process would increase heat,
so maybe that is a clear benefit.
  • 2 0
 @blcpdx: I think you are on the right track but still kind of missing a few key elements. The neopos/deaneasy token is still increasing the progressivity of the air spring over running the fork with no tokens. The primary aim of using a dynamic (Compressible) token over a rigid one is to get the mid-stroke support benefits of a token but decrease the end stroke ramp up inherent to the system. Look at the chart on the formula page to explain this a little better.

----> www.rideformula.com/technologies/neopos

note that on this chart the gray line indicates a standard rigid token and "standard" is the fork without volume spacers. Both the standard and neopos are both more progressive that the standard system with no form of token in it. Now take a look at the spring curve chart labeled figure 9 in the article above. The carbon air insert is less progressive than even the standard set up with no tokens. So it is effectively the complete opposite of a token, it is a volume sink or essentially a "negative token".

Many are probably thinking why would I want to do this when tokens are so popular and work so well for many people? While that is the case for some riders there are those at the other end of the spectrum like lightweight riders who have trouble getting full travel while maintaining mid body support who could really benefit from this. This is just one application of the material though. Putting it in the negative chamber is a totally different story.
  • 1 1
 thanks @mixmastamikal, I *think* maybe I understand it better now.

I think your description as the "volume sink" is a very apt one, and
better illustrates the concept than the rather esoteric "adsorbtion".
What I imagine happening, based on the chart,
is that as the piston compresses, the CarbonAir is whisking the air into its nether-regions,
so that the pressure comes up more slowly.
Or, as you said in your initial response, "the opposite of a volume spacer."

I also think you're correct in your assertion that
"many are probably thinking why would I want to do this?"

Mr Stott does say, in describing the limitations of conventional spacers, that they "[increase] progressiveness, making it harder to bottom-out for a given amount of sag."

But I think he (CarbonAir?) could probably be clearer about the intended user for this product,
or I could stand to be more obsessive about setting up my sag,
and therefore immediately identify the problem this solves.

From what you're saying, it's simply the equivalent tool for lighter riders,
that conventional volume spacers are for heavier riders (or those with a "heavier" riding style)
In the same way larger riders would typically have to jack up the pressure to get support,
lighter riders sometimes have to take a bunch out to get any movement from the suspension.

Each type of spacer allows the rider to keep the pressure of the fork at its optimum range,
while accomodating their unique weight or riding style.

Like I said, I think it's all in there, but maybe overshadowed by jargon.

Cheers!
  • 1 0
 @mixmastamikal:
P.S. with a title claiming to "make air suspension more like coil"
I would have expected to have a coil shock spring rate somewhere on the charts.

It might help for them to have an animated chart,
showing of how their curve compares to a coil spring,
and how adjusting the air pressure basically equates to an infinitely adjustable coil spring
(vs the small assortment for actual coil springs)

Just my humble opinion, but I think their pitch needs work, maybe they should hire you Wink
  • 2 0
 RS should start from getting rid of this stupid digressive compression tunes from their shocks.
  • 1 0
 This is a super cool application of activated carbon! I'll be interested to give it a shot, especially as a relatively light rider with a 180mm Lyrik.
  • 4 5
 This is a cool idea, but Jesus H christ, this is getting like the Valve vs solid state guitar amp discussion. Air forks are always trying to replicate coil forks, if you really want that feel, ride a coil fork. Both air forks and solid state amps are technically superior, but Coil and Valve feel better, ride whatever you like, stop trying to make one into the other.
  • 2 0
 Why wouldn’t you want the light weight and tunability of air combined with the initial spring curve of coil?

Let’s get the best of both worlds.
  • 2 1
 A lot of folks such as myself really enjoy the fit and forget factor with coil forks, not everyone wants to spend their life dicking about with fork settings.
  • 1 0
 @dbxrace: okay. So keep riding coil forks. No need to complain about people trying to improve air forks
  • 2 0
 This is one of my favourite articles! Love the physics part, great written, even for muppets like me
  • 2 0
 All I know is that video is top-notch production marketing material. I'm sold.
  • 2 0
 It was my believe that everyone aims to make air suspension more like coil?
  • 1 0
 Van der Waal cried out 'Eureka' when he figured folding his clothes took up less room in his closet than not folding. Or maybe that was his wife that yelled it at him.
  • 2 0
 is it the same like riding a coil fork then ? that would be really cool. It would be like riding my coil spring fork then.
  • 2 0
 "...Carbon Air Aims to Make Air Suspension More Like Coil..." How often did we hear that in the last ten years ??
  • 3 3
 like anyone here remembers the difference. it's more like... "Grandpa, can you tell us the story about coil forks and shocks again?"
  • 4 1
 does it absorve Covid?
  • 2 0
 Ok, but how do you put 20 football fields inside one stancion?
  • 2 0
 This could be great for smaller riders!
  • 3 0
 Are they edible?
  • 1 1
 It's funny there at this point when other then durability Air is better then could on the fork side. I went High end Air to a Coild and lost small bump at this point..
  • 2 0
 What if I like the progressivity of my air fork?
  • 1 0
 We could skip the whole heat ramp up on compression issue by using nitrogen rather than air..
  • 1 0
 So you put something in a jar, that creates more space in the jar than there was before you put something in the jar.
  • 1 0
 so this could be great cheap thing to put in with a moco damper which is pretty progressive??
  • 1 0
 Damm, it is very cool, but with plus 65 gr. there is the old good spring that can do it better....
  • 1 0
 To protect this from oil, one could possibly contain it in a sealed pressurizable bladder.
  • 2 1
 Just the other day I was saying how I wish forks were more expensive.
  • 2 0
 Rollin Coal
  • 1 0
 This looks exactly like what I Dont want
  • 1 0
 fibonacci sequence make my fork feel good
  • 1 1
 So at 1/400th of a second compression and rebound response, why can’t we fill a tire with this foam?
  • 1 0
 I bet ten burpees a day will make you faster and it’s free
  • 1 0
 What about oil adsorption? Meaning won't this get soaked in lubricant?
  • 1 0
 My thoughts exactly, I always store my bikes hanging by the front wheel. Not so much of a problem in a car.
  • 1 0
 @ziplockk: Or when used in the negative chamber, but the idea is great anyway
  • 1 0
 I'm waiting for the Adidas ultra boost fork to hit the market in 2022 !
  • 1 0
 You know what feels like a coil spring???
A coil spring!
  • 1 0
 I would love to try this, but only if it's really expensive.
  • 1 0
 This is super smart! Can’t wait to see mtb applications Smile
  • 1 0
 I’m very excited about this technology for aftermarket. Count me in!
  • 1 0
 air to feel like coil?!?!? why not just buy coil
  • 1 1
 Is anyone not aiming to make air suspension like coil these days?
  • 2 0
 I've actually read it now. Sounds like an awesome product. I had this exact issue with a meg neg, it made the first 2/3 of the travel feel really good, but was then way too progressive. That meg neg graph above is exactly what I was after. Awesome write up as well!
  • 1 1
 And what if we filled the fork with helium too?
  • 1 0
 FLipping Awesome Concept
  • 1 0
 It's science.
  • 2 2
 My head hurts and I’ve only had one dark and stormy...
  • 1 0
 Very nice! How much?
  • 1 0
 please make it stop.
  • 3 6
 Does Formula have anything to say about this? maybe neopos??
  • 6 1
 They do completely opposite things. One increases the size of a given air chamber; the other decreases it. It's explained in the article.
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