Pinkbike Poll - Air Suspension in World Cup Downhilling

Mar 8, 2013 at 0:09
Mar 8, 2013
by Mike Levy  
 
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Will there be a day when the majority of top-flight downhillers are on air sprung bikes regardless of the course?

As it is right now, most suspension companies manufacture both an air-sprung fork and shock intended for downhill use, with strong rumors of others about to debut their own new platforms to the world. That isn't surprising, of course, given that the general perception among many consumers being that air springs mean premier suspension, and pricing and nomenclature also supports this. What is odd, though, is that this train of thought persists despite many sponsored World Cup downhillers preferring to use coil-sprung alternatives on their race bikes. There is no hiding this fact when talking about the back of the bike as it is pretty easy to spot a coil or air-sprung shock, but it gets a little murky when it comes to forks - it's no secret that some riders who's forks not only have the decals of the air-sprung version but also the corresponding air cap, are actually running a coil inside. The world's fastest racers are a particular bunch and if some of them feel more comfortable with a coil-sprung fork, that is what they will run come race day. I believe that we will see a shift away from coil springs in the future, though, with air becoming the predominant method of holding up a World Cup downhill race bike within the next five years.

Steve Smith smashing a run down. He qualified fourth on the day about 3 seconds out of the pole position.

Devinci's Steve Smith on his RockShox BoXXer at the Fort William World Cup. Is his works BlackBox fork fitted with a coil spring, or an air system?




KHS's logan Binggeli on his air-sprung Manitou Dorado.
Why it will happen

Air springs offer both lighter weight and limitless spring rate options that, at first glance, should make them the obvious choice for a racer, but there is far more to the equation than just those two facts. On the other side of the coin there is increased friction caused by the seals required by the air spring and the increased seal surface area, increases in spring rate as temps go up under hard use (remember that air expands as its warms up), and fluctuating damping levels due to both the air spring's rate changing and heat build-up. Admittedly, those sound like some serious issues that any rider would want to avoid, but some top racers currently choose to run springs on less demanding courses. The last few years have seen engineers make up ground in those battles: look at RockShox's 'Hot Rod' damper needle that is claimed to compensate for heat build-up with its "thermoplastic resin core" that is said to allow it to change shape slightly as temps rise, the slippery stanchion treatments (Kashima from FOX, BlackGold from RockShox, and Gold Slick Ano from X-Fusion) that have become de rigueur, and internal trickery like the just released 'Counter Measure' negative spring that RockShox has been using in their BlackBox Vivid shocks and is now putting into production. FOX's Dual Rate Control Valve shocks have even allowed engineers to tune the shock's air spring rate and curve like never before, although that technology was developed largely by Trek's suspension lab in partnership with FOX and won't likely be employed on another brand's bikes.

One trait of an air spring that no amount of smart engineers locked together in a room can solve is their inherent rising rate. A coil spring that is labelled as having a 400lb/in rate (meaning it takes 400lb to compress it one inch) will compress in a linear fashion, but an air spring will ramp up in rate as it is compressed. This fact can be used by engineers who design their bike around the characteristics of an air shock, but it also means that certain bikes will never meet their potential if their stock coil-sprung shock is swapped out for an air unit (the opposite can also be true).

An ecstatic Justin Frey working over Gwin s new RAD 40 forks.

FOX's Justin Frey working on Aaron Gwin's RAD 40 fork. Is Gwin's works fork air-sprung?

bigquotesThe spring system is unlike anything out there in the gravity suspension world. It is a 100% FOX design that has several different adjustments for individual riders' weight and riding style. It is not a hybrid system. The Trek World Racing team races on FOX designed spring systems. - Mark Fitzsimmons, FOX's Race Program Director

The worlds of motocross and supercross are often looked at as the leading edge of suspension technology, and the 2013 season has seen nearly all of the top 450 riders make the move to either the Showa or KYB air forks, with the majority of them reportedly very happy with the performance. Word is that it isn't just the 2 - 3lb weight loss, but also the improved overall feel that the riders are fans of. Yes, the terrain that they race on is markedly different from a World Cup downhill track, but it is probably fair to say that the average supercross racer is far more demanding and in-tune with their suspension than most World Cup downhillers. It is only after extensive testing on private tracks and with their own private suspension technicians that those riders will run an air fork when it counts, and that is exactly what we've seen happen. Granted, massive resources in the sport allow Showa and KYB to manufacture expensive one-off internal parts that have first-rate tolerances, as well as include insanely expensive stanchion and damper rod coatings that take suppleness to the next level, but it is a clear sign that air is better, even if it takes more money to make it so. It is only a matter of time until we see less expensive methods and lighter weight parts used within the works-level forks of the world's fastest downhillers. KTM's Ryan Dungey even used a air-sprung rear shock for a few supercross rounds before a seal failure saw his bike sag to bottom out as the gates dropped (reportedly due to the harmonics of the bike as he brought the revs up to start the moto).



Levy's Take:
bigquotesThere is no doubt in my mind that there will be a time when we see air-sprung forks and shocks widely accepted as the best equipment for World Cup downhill racing. It certainly won't be next season, or even within the next two or three years, but I don't feel like I'm going out on a limb when I say that racers will be choosing air over coils within five years time. The challenges of increased seal surface area (and therefore increased friction) and consistent damping will be met by advancing technology that pushes air ahead of coil when talking about both performance and reliability, allowing riders to reap the benefits of infinite spring rate adjustment and lighter weight. It is only a matter of time.
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222 Comments

  • + 59
 Not saying that it applies on bicycles. But look at the AMA Supercross this season. Everyone on air-forks are riding far from consistent. Looking at the Villopoto crashes this year, they all are so unusual for him. Chad had some back luck with air as well, now when he switches from Air to Coil, BOOM he's back. Air suspension is lighter, but I don't think that it gives the traction front-end as good as Ti coil. Thats my personal opinion, I might be wrong.
  • - 1
 Traction is very similar. Especialy on a fork that has as much stiction as in MX. That's not an issue. Reliability might be since but the races are way longer. Notice how solo air in RS is a very reliable air spring system
  • + 7
 I agree with you reinholds. My suspicion is that it's a similar effect to lack of small bump compliance and resulting skate or slide that you might see in/on road going cars and bikes when the EVERYTHING is setup real stiff.

Coil setups are still more responsive and compliant over the small stuff and that's where a good deal of your traction is.
  • + 6
 when it comes to rear shocks im coil for life unless its XC or SS. right now im running boxxer wc and im sold on them, i love them. but i dont think we will ever reach the day when coil is out of the picture, all in all it comes down to affordability and personal preference. im not to weight weenie so it all comes down to affordability and function for me.
  • - 1
 its very difficult, and almost irrelevant to compare automotive vehicles like motorbikes to bicycles

the factor missing in this comparison, is the ratio of the vehicle weight to the rider

motorbikes are many factors heavier than a bicycle (even a 40lb DH bike) and this imbalance in vehicle/rider should always be counted by examining differences in suspension technology between the 2 vehicles as it has a massive influence on spring type, seal friction, oil volumes and damping
  • + 4
 Actually, I dont see how the ratio of rider weight to vehicle weight influences anything at all (the spring LEAST of all!). It doesnt matter if it has to suspend a bike and rider, a car and driver, or three elephants riding each other's backs while jumping on a trampoline. Suspension has to be designed for a certain range of forces, speeds and amplitudes, those dictate the needs for the suspension.
  • + 1
 Good to know by the way reinholds!
  • + 4
 @ hampsteadbandit
As I told I'm not comparing motocross suspension to bicycle suspension. I'm saying that air in the forks does not work that well, and why it's needed in first place. I can agree with cretin82, that RockShox got it sorted out and WC solo air is giving rather consistent and solid performance, but apart from weight, it's not better then Boxxer coil. So in general, it's just search for a weight save, and that counts on WC level racers only.
In short, what is the point of technology that doesn't accel, but just tries to imitate other technologies action that has been finetuned for two decades now.
And I'll want to see if tomorrow Chad is back on air-suspenion. I would bet a tenner that he'll ride a coil.
  • + 3
 @hampsteadbandit: You are right, but in spite of all those differences, things like compliance are a constant. Something that's not as soft in the initial part of it's travel, and therefore can't respond fast enough to small(er) irregularties in surface, is more likely to lose traction. The things you mentioned: spring type, seal friction, oil volumes and damping affect the bikes (or whatever) ability to stay in contact with the road.

No contact with the road (or should I say no "weighted" contact) with the ground means you're asking for a slide (Kind of why you want to be real careful about applying power over rises in the middle of turns).

My experience with air stuff is that it's not responsive enough to small stuff to do as a good job of maintaining traction as a coil setup.
  • + 2
 Dungy loves the air on his KTM, like the poll says, when technology allows it to be more consistent, the industry with thrive on air 100%
  • + 4
 People will buy whatever the companies with the best adverising and marketing want to sell them.

I know for a fact that my air Totem is nowhere near as good as my mate's coil totem, or my coil domain, in terms of action. I wish I got a coil one to be honest. I know you can change it, but I'm too lazy and tight. What an idiot, buying an air fork to save 120g that I won't notice. Also, the compression damping adjuster is pretty much superfluous, because the air spring is so progressive as to not allow the fork to bottom out even with 50% sag and no compression damping set. Air springs are too inconsistent to allow the damping to be completely independent from the springing. If you want buttery smooth action, you have to strip it down every five hours or something.

As advancements are made in seal technology to allow less friction, the same advancements can be applied to coil shocks (doh?).

I can't see it happening as the article predicts, but I can see it being marketing driven. Perhaps the fork manufacturers want it because it's cheaper for them to make air springs and they don't have to rely on external suppliers. Easier to tune to bodyweight too, but air will never be as good as coil in terms of performance.
  • + 1
 I think the biggest difference between the motocross and bicycle air suspension is the amount of time in them. for example in bikes we have overall pretty reliable and great performing air suspension simply because of the amount of development that has gone into it. if we look back at some of the older air suspension available to bikes, they were no where close in terms of performance and reliability compared to todays air suspension. and with the amount of development and research going into it, it will only get better. the same goes for motocross suspension except that air suspension is still a very new technology for motocross and supercross. since it is a new technology for moto, there needs to be research done for it to be able to perform better, mainly in reliability. because the demands placed on motorcycle suspension during a race and bicycle suspension is so much different, the motocross world simply needs to do research and development on how to make air work for the type of riding, a little bit like how we have different styles of air forks and shocks that are meant for different types of riding(xc,am,fr,dh) and are built to handle that type of riding. so in the end i believe that motocross will eventually use air suspension more once the technology allows it to work better for motorcycles.
  • + 1
 @Reinholds: I think world cup boxxers are by far the best and I owned 2010 boxxer rc, 2010 boxxer r2c2 and the adjust-ability was balls. At least you can use a shock pump and tune your fork, & it's lighter.
  • + 1
 Just for argument sake. And I don't know if this is true at all, but. I would think that the moto forks would be filled with nitrogen. Nitrogen is inert and does not change volume with temperature. This should make for a completely consistent spring rate even as the fork internals warm up from repeated movement. The only thing that would affect the performance consistency would be the dropping viscosity of the oil as it warms up.
I know for a fact this is why Aircraft landing gear oleos are charged with nitrogen. Works for Airbus and Boeing, probably work in a Motocross bike.
As for MTB, I love my Fox 36 Float, 32 831 and RS Revelation, all air. I had an 888 WC ATA (Air) and converted it to Ti spring which performed much better. So for DH I go coil and AM, DJ go air.
  • + 1
 It's personal preference.
  • + 1
 Reinholds it's not apart from weight - solo air in boxxers is for adjustability.
  • + 3
 What are the extra adjustability of the Solo Air? If we compare WC to R2C2, the both have: beginning and ending-stroke rebound, high and low-speed compression, Internal Pre-load (or air volume adjustment in air), and in the Solo Air you pump in the air to make change the air spring weight, while in R2C2 you change the coil spring itself. You can get aftermarket coils with as detailed lbs change as you can pump the air. I don't see any extra adjustment in Solo Air.
Just two notes: 1. When Air springs fails, your run is over, while on coil you can still ride down the mountain on broken spring, to change it. 2. We saw it when Dungey's back end just collapsed in heat race this year. I have never seen that happen with coil shock, the same applies to bicycles, if the air sping fails, in best case, your race run is over, in worst case it follow with bad crash.
  • + 2
 You can adjust the spring in way smaller increments and you can adjust it very fast. Changing the spring takes time. Not to mention most springs have a large margin of error so they won't be as accurate. Though tell me where I can find aftermarket coils in small increments for the boxxer with a very small erorr.

Also when solo air fails. That's a null argument. If a spring breaks your race run is over also as you won't get a good result with a wonky characteristic anyway. You don't race for 30th spot. Not to mention solo air doesn't fail. 3 years on mine. Heavy use. Managed to kill my damper when I bottomed HARD after going too fast on a road gap and riding over a stone half the size of my wheel. The air spring was ok. But yeah in the 1 in a million case it fails and then your race run is more over than with a coil where you are just far away from the podium instead of DNF. A snakebite does the same yet we don't run solid tires Wink
  • + 2
 In all my years mountainbiking I've seen one broken spring and the guy didn't even know it was broken, he just thought it needed an overhaul. I've seen air shock failures many times and it can be a ride ender . Air can't match the sensitivity of coil for traction. Look at the Boxxer WC, unless you constantly maintain it they don't feel plush, that's why alot of guys run them too soft. I've never known anyone who runs them at the recommended psi. The cheaper coil spring Boxxers feel much more plush even without the maintenance.
  • + 1
 Not a ton of maintenance. Once a month you clean and change oil in the solo air and it's fine. Yes some air shocks are shit but solo air is proven and reliable.
  • + 1
 All I can say it works for me
  • + 1
 As a freerider, I'd love to see air get perfected a bit more. I love the idea of air due to the rising rate it gives, I bottom out coil forks so excessively that if I have one stiff enough to keep from bottoming, the small bump compliance is gone so I might as well be running an air fork.
  • + 1
 I like air cause I can take a heavier pack and just put more air in or run it with more or less sag with out changing a spring over a much greater range of adjustment. I like coil for not having to dick around so much or worry about leaking seals. Coils are more reliable but, heavier and less adjustable. I have air and coil on my Abra Cadabra rear shock. For a race run where long term reliability isn't an issue air rules. For freeride where big hits require progressive rates air, for Allmountain where weight counts air. For abusive downhillers who hate maintenance coils will allways work.
  • + 0
 I don't want to overhaul my air fork every month, or every couple weeks if it's bad weather and I'm riding alot. And even then I just don't think an air shock is as plush and compliant as a coil, the bound wire is just so sensitive and has a perfect natural progressive spring rate that cannot be matched by negative springs or other air gimmickery. But the main advantage of coil is small bump compliance which translates to better traction. Comparing mountain bikes and motorcycles is not really fair because the heavy weight of a motorcycle makes the initial stiction of an air shock less of an issue. A bicycle weighs alot less so the stiction of an air shock is more noticeable and that's where the traction control is affected in turns. Had Danny Hart been on a coil shock fork in that turn at PMB last year he probably wouldn't have washed out so easily and crashed. Air shocks are especially not as plush for lighter riders like him.
  • + 1
 If you are riding a fox or RS you have to do that anyway. Also a coil doesn't have a progressive spring rate. It has a lieear spring rate. The small bump compliance is nice but if you ride with a lot of LSC you will not feel the difference anyway. Also the Danny Hart comment is pure speculation. Most top pros ride on very hard forks both in damping and spring rate so small difference in supple hits it not that noticeable.
  • + 0
 True about the maintenance. Apart from Marzocchi every other fork needs to have it done regularly. Don't mistake the linear spring rate to flat rate. Linear spring rate needs gradual force increase to go into deeper travel. The point of the fork, in a race run, is to use all of the travel, otherwise we can run 2" suspensions instead. If the air fork is as progressive as some charts show, it's close to impossible to use full its travel, and it's "dead" on the bump absorption as well. So both ends of the stroke aren't usable, the start and the end, leaving mid section sort of usable. Still doesn't make a lot of sense. Only air fork I'm really looking forward to is the DVO Emerald, I'm 100% sure that they'll get it deal'd in. The controlled flex of the inverted fork will provide that traction needed.
  • + 0
 I can say it only for the solo air - it isn't that progressive (unless you set up the bottom out like an idiot, did it once... don't ask why). Please don't speculate on a fork you never tried. I shipped on a boxxer wc from a 07 zoke 888 rc2x and felt the fork was better than the zoke. Yes it was after some tinkering (by sram holland if the first owner was saying the truth) but it was super smooth.

As for every other fork wrong again - dorado doesnt or any fork with an ava cart in it Wink
  • + 1
 Don't Marzocchi forks get weighed without any oil at all? I will admit the 888 evo ti's feel the best. You pay with a ton of added on weight because they're full of oil and they got a coil.
  • + 1
 Basically air isn't as good as coil and it never will be in terms of performance. But performance isn't the only factor.

My Totem is Dual Position Air. It is reliable, reliably sticky. It's never blown up, but it dosn't work as well as my DJ3 with no air preload. I've also got a Monarch Plus RC3 air shock, which is billed as an AM/enduro option. It is totally shit when the temperature gets over 30 or a DH lasts more than a minute. I'll never buy another air shock because they simply are not as good as coil shocks. 400g is a small price to pay for proper function.
  • + 1
 @spaced Me saying Danny Hart washing out his front tire at PMB because he didn't have a coil fork is no more speculation than saying DH bikes will have air springs because motorcycles do now. If anything I make a stronger argument than Levy because he is talking about apples & oranges when he makes speculation about DH based upon what has happened in motocross.
  • + 1
 @Protour not really. A LOT of MX technology has already been transfered to dh. The comment about MX/DH was marely observing a pattern. What you did was pure speculation based on no real life evidence and with no idea about pro rider suspension setup.

@BroJo - newer marz are weighted properly and their true weight is closer to what's posted on their site. The new ti zokes are not as stupid heavy as they were in the past. If I didn't like the adjustability of the air and the lack of support for LSC in marz I'd go for the ti defo. I love my 44 rc3 ti.

@jaame your problem isn't that air is not as good in terms of performance. Your problem is that you have bought shitty products Wink
  • + 2
 If you look one article further up the Pinkbike homepage, there's one about the new Vivid and Vivid Air. In one box, it opens with something along the lines of "Air will never offer the same sensitivity as coil because it has more seals". That is an inescapable fact. It doesn't matter how good they are, or how fancy your coating is, it's still not as good as not having the seals there at all.

@Spaced, you're half right. I know that the Totem doesn't work as well as a lot of other forks with skinny legs, I think the seal surface area on the 40mm legs has a lot to do with it. But they also don't look as good as the Totem. All things considered, including my riding level, the Totem is the best product, not a shitty one.

As for the Monarch Plus, you're right - it is shit. Problem is, the only coil shock I could easily get at the time in a 190 was the CCDB, which is too expensive. I got a sweet deal on the Monarch, and according to the reviews it should have done the business. I don't believe it's any worse than any other air shock, but I do believe that air shocks are shit in general. You don't see air shocks in MotoGP or F1 as far as I know. The only reason people want them is because they are lighter, not because they are better, because they aren't better.
  • + 1
 Yes it won't be as sensitive. The problem is how noticeable the difference is during riding and how does it influence your traction. As for totem - it's a good fork but the 2 step is a shitty system.
  • + 1
 There is no gas that will not expand with temperature. If you control the gas going in, you can know precisely the expansion but you can't avoid it. Planes would use nitrogen because it is easy to dry and you don't want rust or ice anywhere near a plane. I know I am a little late, but I don't see how you could get good loaded performance from an air shock. Hit a rock or root on a berm and the coil moves the same as on flat ground, air is already rising in rate from the compression.
  • + 1
 But rising rate isn't necessairly bad if the frame is designed around a rising rate shock
  • + 1
 @suicidedownhiller

Think you need to work on Damping not spring rate to prevent bottoming. Spring rate is there to make sure the suspension sag is right and that is it! You do not tune travel characteristics with it, that is damping. Bottoming means you need more high speed damping, which will not effect small bump sensitivity.
  • + 2
 You are partially correct but you DO tune the fork with sag/stiffness/air pressure if you have air. If it wasn't the case the pros wouldn't use stiffer suspension. If your arms can handle it for racing you should use as hard suspension as possible if at that setting you still have traction (Set it up right at the fringe). For casual riding, yeah. Set it up softer.
[Reply]
  • + 25
 For all doubters / haters of air, I'm willing to challenge anyone that's willing to travel to my local riding spot (Aston Hill) in a "blind test challenge"

I own a small bike shop, and have 2 demo bikes kitted with top end gear. One Makulu has BOS coil on it and the other has BOS air on it.

I'm willing to let you ride both, and then I will challenge you to tell me, which you think is best / or which one you can tell is air or not.
I will give you a free shop race shirt, if you can, without a doubt, tell me which is which

So there.
  • + 5
 ^if therr is any truth to your words then i am very impressed
  • + 4
 By my challenge or my claim - either way I stand by both Smile

The bikes are in my profile for anyone doubting the validity of my claim that I have the bikes to test.
  • + 16
 50% chance of getting a free jersey!
  • + 4
 Haha, sh!t, didn't think that one through :p
  • + 1
 Surely you could tell by the adjusters (whether it has an air valve or preload adjuster) without even riding the bikes, though they may have a similar ride?
  • + 1
 @sup3rcOw

Aston Hills is not a suitable challenge, because its a "short course" south-eastern UK downhill facility

what are we talking about on the one of the runs like DH3 or whatever they are now called? 1 min 20 seconds??

hardly a 'heat/stress' test or valid comparison for air sprung technology Wink


several years back, I have raced a 160mm all-mountain bike at Aston Hills (after not having ridden at Aston Hills for years) and been in the top 10 against guys riding 200mm DH race bikes...


try taking your Makulu to Whistler Bike Park and riding Garbanzo to Lower Bike Park repeatedly (a good 25 minutes of gnarl) and tell me you don't have issues with air spring rates and rebound control on an air damper / fork??

the old Devinci Wilson (FSR) came in 2005 with air sprung fox shock to save weight, but they soon returned to speccing a coil sprung fox shock for good reasons Wink
  • + 1
 I'll report back then when I'm back from France if you want. Things have changed an awful lot since 2005 Rob.
  • + 1
 thealmightybryn - the forks you wont be able to tell just by looking at them and for the shock... well the idea is not to look, aka blind test Wink
  • + 1
 @sup3rcOw

let us know what you find...

of course I use an air sprung fork on my current 29'er trail bike, but if I bought another DH bike it would be coil sprung front and rear, damn the slight weight penalty, I would always prefer the consistency of coils for the gravity riding scenario
  • + 1
 I have been on the air fork for a good old while. Heating aside (in that as you say, I'll wait till after France to give my unbiased review...I own both after all), the Air fork pisses over the coil.
  • + 1
 A friend of mine was fully air sprung for the Garbanzo dh race and found it fine. on a 25 minute descent there would be a big altitude change but also I don't know if you actually had this problem or just assumed that it will occur on a descent of that length. I've had both coil and air forks, I could ride either but prefer an air fork due to it's progressive spring rate.
  • + 3
 Screw the jersey, getting to ride two bikes on Aston Hill would be awesome!
[Reply]
  • + 19
 It's about time the Fox 40 dabbled into air really, I mean the Boxxer have done it for around 6 years! Them new 40s do look pretty sweet! With regards to this matter, I personally think its what ever the wordcup riders get thrown at them, then us average joeblogs follows!
  • + 9
 aren't the Fox 40's on the Session 9.9 air? But yeah I agree an air 40 for everyone would be awesome!
  • + 7
 Hybrid air*
  • + 1
 www.pinkbike.com/news/Fox-Debuts-New-Downhill-Fork-40-RAD.html

some more details on the 40 Hybrid, I want some so much!
  • + 8
 I don't know much on the issue. However I have heard that air shocks heat up and then turn to balls? Whereas coils can live the dream at any temperature?
  • + 5
 Some coil shocks also have air chambers, its just they have the spring to take the load where the air shock is just an air shock, I believe older air shocks used to have problems but I think todays top end shocks dont fade out unless your on a 1 hour DH beat,

There always going to be air pressure difference when your riding, Heat and altitude will always affect the shock pressures Correct me if im wrong?.
  • + 1
 How much you willing to pay. I have a set.
  • + 0
 does anybody knows when fox is going to release the fox 40 rad ?
  • - 7
 Bos have produced an air triple clamp DH fork that's said to be just as effective as coil, though they always said you'd never get one as effective as coil they have designed a way of doing so, as for Boxxer lets be honest here no they ain't been doing it for 6 years they been trying to push it for 6 years, the first thing everyone does with air boxxers swap them for coil or get them converted LOL As for fox yes the pro's will ride what ever Fox say as they are the biggest sponsorship as for product it's shit I have just sold ever Fox suspension item I have had because i have had enough of the crap they make.
  • + 2
 Trying to push? so what your trying to say is.. they're crap? I agree there probably is a large percentage of people that converted back to coil, clearly people still buy them though? im sure Rockshox would of pulled the product if there was no market, not make the same model of fork with hardly any changes for 3-4Years...
  • - 8
 I think pretty soon everyone will be on these Fox 40s because they are 5mm wider stanchions than the Boxxer WCs, just as light, and have the Kashima coating, which helps a lot. RochShox have to make the Boxxer burlier because they're great for racing, but for everyday riding on agressive trails, everyone will go with a Fox 40.
  • + 1
 Force vs travel curve is not linear with an air sprung suspension. When you reach the end of stroke on an air suspension, the force required to compress the spring goes up exponentially forums.bajasae.net/forum/uploads/179/FoxFLOATForceVsCompression.JPG
An other major problem with an air spring is that the air gets progressively hotter (P*V = n*R*T) hence if the temperature goes up and the volume does not change, pressure goes up. All of these problems are not found on with conventionnal spring setup. Air makes sense in XC or AM applications where weight is more of a concern, but as far as DH goes, coil springs are here to stay.
  • + 1
 yes but a 40 air makes more sense than a boxxer wc, its larger internal diameter of the sanctions means that it will need significantly lower pressures to support the same rider weight, lower pressure means that the heating effect becomes less significant and if the lowers are aluminium as believed then it could be used like a heat sink to remove the excess heat from the chamber, basically the technology for an air spring is all there its just a question of have they pulled it off ??
  • + 1
 Am I the only one who finds it funny that Fox pulled out of the motocross game years ago because they wanted to do everything air and now they are only making a Coil DH fork, not air?
  • + 1
 erm... no mention that if you fill them with nitrogen (like most tuning companies do with rear shocks) there is much less effect on temperature and therefore pressure
  • + 4
 See what happened in motocross factory racers, James stewart and ryan dungey they switched back to springs because of lack of responsiveness. they said AIR was to lazy for hardcore tracks.
  • + 1
 I would actually think a higher pressure reduces temperatures: higher pressure means higher density means more molecules means more mass means more heat capacity means lower temperatures for same heat input. Also, the absolute pressures may be higher, the compression ratio is still the same.
  • + 2
 @JakeNeaves your right dude air fades very quickly, thats why they combined air, fluid and springs. I stick with what works lol. Im not like every one who has to have the lighest stuff. its like people that have iphones lol. "I make calls"
  • + 1
 I've had 2 air forks for dh and always ran a coil shock for dh. I've ridden tracks like fort bill on hot days (25-30 degrees) and never experienced any sort of fade from boxxer wcs and expect my dorados to be the same. I personally like thenon-linear curve provided by air forks.
  • + 1
 higher air pressure means more air molecules pressed up against each other so there will be more friction when they try and move around creating more heat which makes a larger difference to pressure, psi = pounds per square inch, the more square inches of volume there are the more lbs of force there will be per psi so larger volumes are better than small volumes. (pv=nrt)

its not damping fade you experience, as the shock gets ridden harder the spring rate gets firmer the more the shock heats up.
this means that more rebound is needed to control the spring rate etc....

shocks are harder to make work than forks as a rear shock needs higher pressures due to the leverage rate of the rear suspension,for example a 222x 70 rear shock operating 8 inches of rear suspension has approximately a 2.8 : 1 leverage ratio, for every 1inch the shock moves the wheel moves 2.8, so the shock needs around 2.8 times more pressure than a fork would to sustain the same spring rate, this means heat build up is a significantly larger factor, hence rockshox have been using solo air for years in their downhill forks but their air shock for dh bikes is a significantly newer addition
  • + 1
 Actually the internal friction (viscosity) of gases hardly changes with pressure at all; air only 5% more at 1000psi than at 15psi. Wikipedia on viscosity in gases: "So an increase in density due to an increase in pressure doesn't result in any change in viscosity". However changes in temperature cause significant changes in viscosity; easily 12% for 50 degrees.

Furthermore the compression and the expansion of air in an air spring are approximately adiabatic, the air cools down on expansion almost as much as it heats up during compression. There are small losses due to internal friction and due to heat exchange with the container though. The heat generated in the air spring is completely negligible compared to the heat dissipated in the damper. Almost all heat buildup in the air spring comes from heat exchange with the damper parts. Which makes perfect sense: you dont use a spring to dissipate energy, then it wouldnt spring!, the damper is there to dissipate kinetic energy into heat.

"square inches of volume"? Wink I though area was inches squared? Only the pressure on the cross sectional area of the piston matters. So it doesnt need 2.8 times more pressure, it needs the product of pressure and piston area to be 2.8 times more, to get the same force as the front; psi*A=force.
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  • + 16
 Ti coils forever. Watched my friend blow out his air shock 3 times in a year. I run a Marzo 888 up front and have ridden out of Black Rock dripping oil without much downfall. Then again, I hate racing and love jumping so I don't have the downhiller perspective on things... tis for you weight weenies who look into things too much IMHO.
  • + 7
 Have fun. If you ride DH or FR you are more privileged than 95% of society at least. Huck and shred. I really miss my BMX days... things were so simple
  • + 1
 Air is not for weight. You can set up your fork/shock for different trails. Steep - you make the front end stiffer not to go OTB, can also adjust it for bigger hits. Also not all air shocks suck
  • + 2
 Marrz 888,s use a coil and low pressure air to make up the spring.
  • + 1
 After 6 months on 888 evo v2 ti forks I'm glad to be off them and onto an air fork. Marzocchi aren't entirely problem free after having my stanchion coating flake off and they are very linear even with the volume adjust cranked up and on a heavy spring for a 150-160lb rider.
  • + 1
 I'm on an ava carted boxxer wc and I also have litle problems. Preference. Air isn't really inferior.
  • + 1
 @Spaced your spring (air or coil) is not to stiffen the suspension, it is to set sag. Want stiffer suspension then set the bloody Damping right!
  • + 1
 You are basicly arguing the definition of stiff suspension here. I know what damping does. Also more air makes the fork harder doesn't it? You can fine to it to your preference. Not just set it up to what some guy on the internet told you.
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  • + 11
 For a World Cup rider, sure. Why wouldn't you use air suspension? It only has to be reliable enough to last through one or two runs, then your mechanic will rebuild it for you.
  • + 2
 I run a pair of boxxer WCs and they have held their air perfectly; even over a five month period of recovery where the bike was garaged and untouched. However at slow speeds and low impact hits while seated i find them to have a little more stiction than coil versions, but this has never been noticable once my riding weight is off the saddle and moving
  • - 8
 The problem is the linearity. Every air-fork dives which feels like shit in steep sections.
  • + 1
 Tabletop, what nonsense. The general problem with air forks, that they are progressive - not being linear.
  • + 1
 If you;re referring to blowing through travel, that's entirely different.
  • - 5
 Just inform yourself about basic physics and you'll see that an air-sprugn fork will never be as linear as a coil-sprung fork. Blowing through travel is another effect of this. An air shock or fork "packs up" during many fast hits (brake bump chatter) because of how air molecules behave when they get compressed.
  • + 2
 Your post suggested that you were saying that Air forks were linear in nature - re-read your OP.
  • + 1
 all i use is air sprung forks and for me i find them way nicer and smoother then a coil sprung fork. no problems with mine and with coil forks all i have is problems.
  • + 1
 Diving, blowing through travel, too progressive, harsh bottom out, bottomless, mushy midstroke, whatever you want to call things, they can ALL be a characteristic of air suspension depending on the compression ratio (the ratio of volume at top-out to the volume at bottom-out) and the synergy between frame and air shock.
  • + 1
 tabletop, sorry to break it to you, but seriously.. you're full of sh*t!
Air shocks are more progressive than coil shocks. Period.
Engineers are just trying to get them as linear as possible to get a coil-like feel, but there was never a problem with too linear air suspension, ever! Besides that, the dive you are talking about comes from lack of (lowspeed) compression damping. Instead of talking (wrong?!) physics, you should better take a chance at learning to properly set up your fork... no offense, dude.

I'm riding full air setup front&rear for over a year now on my DH bike and I love it... I changed both from coil and I would never go back.
  • + 2
 "seriously.. you're full of sh*t!" .. "no offense, dude" Big Grin


They are not designing for most linear possible by the way, nor for coil-like feel. They are trying to design for best performance for intended purposes, which is rather linear but some amount of progression is generally preferred. They are actually trying to give air a springrate-curve that is advantageous over the linear rate of a coil.

Tabletop is trying(!) to describe air springs with much too big a volume btw.
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  • + 4
 There are already Race worthy air shocks (CCDBA and BOS Void), and forks (Boxxer WC, BOS Idylle R), so yes, for me, they all will eventually (as long as their sponsor has a DH capable air shock ... ). Hell even in the MX world they are starting to use air sprung suspension heh Smile
  • + 11
 Let`s differenciate between hype and physics/applied engineering.

Physics says airshocks are only half of the equation. In fact they are just dampers that exhibit a bit of non linear springiness. (It can be made to work but it is not a proper technical solution)
Airshocks with springs exhibit nonlinear damping and linear springiness. (Applicationspecific - can be ok)
Oilshocks with springs are linear damping and linear springiness. (Timeproven, reliable design)

Air heats up - all settings go out of the window.

Oilshocks can be designed to show very consistent performance over a wide range of temperature.

Air and grime will kill your shock in no time. Oilshocks will suspend grit in solution and keep the internal parts lubricated. They will wear better and last longer.

Hype: Driver X says prefers airshock X because the Mfg. told him so. That they have dozens of fresh shocks in the drawer at the race and mount a fresh one eachtime because they are afraid that it might fail in the next race.

Economics: Airshock are cheap to manufacture. Oil/spring shocks are more involved. Airshocks are easier on the dealer - he might find a setting,by luck, without having to invest in dozens of springs and fiddle around with something he still does not understand.

Now what do the big boys at Dakar and other venues use? Right, Coilovers with oil and inert gas top up - if space allows 4-6 per axle and large finned cooling tanks for the oil.

Maybe bicycles need more than two shocks? A way to cool the air? Or maybe they need more damping oil in an expansion tank?
  • + 3
 2Stage bike ran 2 air rear shocks! it was great to ride but trying to keep on top of worn bushings was terrible!

www.pinkbike.com/photo/4899279
  • + 8
 @Wakaba except the air is the spring, not the damper.
  • + 1
 I thought about this "air or coil" thing a lot and came up with something very similar you say. It is relevant to build hybrids but air alone won't get the job done. It is good if you want a light fork or maybe a very stiff one (for xc) but as you hit the rough stuff you will know that something is not right.
  • + 5
 I found what you say being a bit confusing.

Normally a shock contains a hydraulic (oil) damper and a mechanical (normally coil) or a pneumatic (air) spring. I also know of pneumatic dampers but they quite rare.

Mechanical springs are normally linear but can also be made progressive. It is also possible to vary the air springs characteristics by having different shapes of the air chamber.
  • + 1
 Exactly faktor66.
By the way, there are plenty of systems that let the air pressure of a separate chamber influence the damping, like the IFP ("instant floating piston") found on FOX shocks, or the bladder DVO will use in the Emerald.
  • + 1
 air shocks are cheaper to manufacture lol
  • + 1
 Karpiel Apocalypse ran one coil, one air. The coil handled the small-to-mid bumps, the air allowed the coil's shock mount to move on the big hits.
  • + 1
 @joefloath: An airshock is just a damper. it is not a spring. Only half of the equation. In the process of compression it turns momentun into heat and looses the heat.Not energy conservation like in a spring. It is something that collapses and then slowly rebounds because of negative suspension movement/rider movement. Only in equilibrium (if you sit quitely on your bike) can you talk of mm spring action. Move a little bit and it turns into a progressive damper. A proper coilover oilshock does none of the above.

@faktor66: If you make an coilspring nonlinear - something is seriously wrong with your suspension. Ex: VW uses nonlinear coilsprings on their cheap ass mcpherson premium. Cheap. If you upgrade - McPherson with airbags. Does it get better? No it is wrong from the beginning.

@baca: Yes, airshocks are cheap to manufacture - think spraycan with valve, two extra seals and a plunger. OEM is "shockingly" low.

As always gotta think why Mfg. push things. For your benefit? Hardly - it is always about bottom line.
  • + 1
 Haha wth are you on about wakaba. Lets be clear: a shock absorber is a unit/system that consists of a damping element combined with a springing element. Damper dissipates kinetic energy to heat. Spring stores and releases kinetic energy. So the airshock consists of a damper/dashpot AND an air spring. Air chambers sure as hell store energy and act like a bloody spring when compressed! How else could the bike come up again? How else could you even ride it? "negative suspension movement/rider movement"? Wth is that? Have you never blown up a balloon? Squeezed a balloon? Pulled or pushed on a syringe? Tried to manually turn over a combustion engine (i.e. kickstart)? Ridden air suspension? With compression and rebound all the way open (no piggyback pressure)? Have you ever felt damping? Removed the coil and moved the suspension? Go do it now please. If you only have air suspension you would have to remove the air chamber barrels/sleeves and remove all piggyback pressure and hold the piggy valve open, for the shock. For fork you'd have to remove the complete unit from one leg and and remove all pressure and hold the valve open, on the other.

Furthermore the rate of a coilspring is not perfectly linear anymore as soon as the diameter of windings or spacing of windings changes. Go look at the springs in your fork and car now please. There is a massive aftermarket for all kinds of springs for cars; linear, progressive, dual rate. Also in cars there is often support springs, which also make the overall rate non-linear.

Air suspension generally combines multiple inherently progressive air springs (separate chambers) to create an overall more linear rate.
  • + 0
 Oh and if you cant control secondary pressures, e.g. fox float stuff, you cant even remotely approximate pure damping, nor pure springing, cus they have a separate, fixed, chamber filled with air (nitrogen actually) that is influencing damping and acting as a light spring at the same time.
  • + 1
 Oh I'm sorry, I just tried, its fine just removing main air pressure really. If its on the bike, you have enough leverage on the rear, and handlebars in front, to work the suspension. Still lots of springing in there, but you can get an idea. Doesnt work with shocks on the bench as I did before though, too much stiction and springing, have to remove barrels and piggyback pressure then.
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  • + 3
 I dont trust air by itself on a suspenscion application, especially in free ride and DH racing. I have a off road background, so I know what will eventually fail We tuned our race truck suspecion wise, but ater so many times we eventually realized u can only tune air itslef so much before it fails or just dosent work. a combination of spring and air is were its at.. If u hammer hard enough especially at a pro level air alone will fail. But we will see in the future what happens.
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  • + 5
 My BOS RaRe air is already better than any other fork I've tried (BOS RaRe coil / Fox 40 kashima / Boxxer )
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  • + 2
 Make Titanium Coil affordable and available for all of the current forks & shocks and we will all be a lot happier!!

Coil for DH...I want to spend my season riding not tuning and rebuilding.

Coil &/ or Air for FR.

Air for AM & XC.
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  • + 4
 Why not use nitrogen instead of "air"? isn't that supposed to be better than just regular air?
I thought it was less prone to heating and stuff...
  • + 19
 why not use helium to save weight
  • + 1
 nitrogen is more stable and less susceptible to heat expansion than normal "air"
  • + 7
 because you need a nitrogen Tank, you can't use your shock pump anymore. and because air is 78% nitrogen
  • - 1
 Your right mate, forks should use nitrogen... When you buy the fork it should come with a tank in nitrogen ( not too big). At ur LBS you should be able to buy small tanks ( take them in your backpack) and the ones that originaly came with your fork... Brilliant ideaa!
  • + 0
 usually almost every car service for trucks has nitrogen tank for their tyres, I have the chance to fill shock and fork, I will try it to see if it make sense
  • + 0
 Actually, nitrogen has a slightly higher gas constant than air (54.99 vs 53.34) which means the pressure will vary MORE with temperature. The only reason nitrogen is used instead of air in some applications is if there are potential oxidation issues in the application (which there are not with a fork).
  • + 4
 Graphs I've been looking at show very little difference in the expansion rates of nitrogen vs air. The difference comes when there is moisture in the air. Pressurizing air changes the dew point. Altering the temperature changes the dew point also. As the moisture changes phase back and forth from liquid to gas, there are big changes in it's volume, which changes the pressure. Nitrogen is known as a dry gas and therefore phase changes are a non issue. This is why it has a reputation for being more stable. So filling your shock with air on a humid day may give less predictable pressure changes than on a dry day. If you did fill your shock on a humid day, let that moist air out on a dry day, and pump it up a few times to purge the moist air. Air springs in forks might be slightly less prone to phase change because they operate at lower pressures and temperatures.
  • + 0
 @patrick2cents

actually they use nitrogen in car tires so the pressure doesn't vary too much hey if it would vary more they would just use normal air : less expensive
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  • + 5
 Why? To save a few grams.

My Lyrik Coil runs much nicer than the air version. Just love its feel.
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  • + 2
 One thing that gives me massive confidence in air is BOS moving into air forks. From what I have heard BOS always states They would never goto air unless they could surpass or match coil. From reports the forks are actually as linear or close to that of coil. I have no doubt air will overrun the coil, with technology improving and overcoming the friction and heating issues and BOS developing a linear air fork add the addition of air adjustability/perfect spring rate and lighter weight forks it is deffinately the future.


I expect the next battle will become air vs USD and coil will slowly remain in the background. Just my opinion though Smile
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  • + 3
 All these technologies developed for air shocks/forks are to make them feel more like coil shocks. hymm.. I'll go with a coil.
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  • + 1
 My last fork was a boxxer world cup. Im now running a boxxer R2C2 and i have to say i like the coil better. Its way more active in its initial stroke. AKA small bump. I think coils will be here for a long time. Unless the air sprung fork can have better small bump, ill never buy an air fork again
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  • + 1
 coil springs are not linear through their compression without being engineered to do that (linear spring) and even when it is a linear spring it is never truly a linear rate but an artificially close to linear rate because as the spring compresses it eventually must become progressive due to the binding of the coils.
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  • + 1
 been riding air sprung front DH fork for 3 years, and i must say i love the feel and suppleness. As long as its a dual air chamber design. single air chamber designs just dont cut it. That being said i just purchased a new coil sprung fork just because it was time and my 3 year old fork wasnt gonna make it till DVO released, even though i wanted to wait. We'll see how a coil feels after so long on air. maybe i'll hate the coil. maybe i'll rediscover something i didn't know i was missing.
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  • + 1
 I believe air pressure changing can be compensated for by pressure sensitive valving in the dampning circut. Is that how the Curtnut valving works? Im curious how many pro DH racers have tried air sprung boxxers?
The weight is not worth mentioning. Ti sprung forks weigh almost the same as air forks. Air has the advantage of being able to fine tune the spring rate.
You could also have a one way check valve that blows off excess air when the pressure reaches too high. The air would be redirrected into an expansion chamber.
  • + 1
 That's right Sshredder, The blow off valve could be pressure adjustable too, reservoir size variable, but there would have to be another valve that lets the air back into the main chamber. This is sort of what I did with my old Sid shock.
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  • + 1
 I'd like to point out that decent adjust ability can be achieved with a standard coil and oil damper setup, provided your basic spring rate is decent for your weight. In the motocross world at least.

Spring preload will move the start point of your force curve, spring rate will decide the gradient. Then you have compression damping in the shock absorber/oil damper, which can alter the gradient based on the speed the fork blows through the travel. E.G a low compression damping will be lovely for small frequent bumps. higher to stiffen the fork up for those big hits. Then you've got rebound adjust as per normal.

Only advantage air has is its lighter weight, and sometimes the rising rate is actually useful. However, i just dont see them overcoming the non-linear curve/heating problems without an incredibly costly and intricate design that wont be practical for the general public
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  • + 1
 Gosh dayum the logic in some of these articles is labyrinthine at best.

"Granted, massive resources in the sport allow Showa and KYB to manufacture expensive one-off internal parts that have first-rate tolerances, as well as include insanely expensive stanchion and damper rod coatings that take suppleness to the next level, but it is a clear sign that air is better, even if it takes more money to make it so."

So something is better in spite of needing far more resources to get working to the same level as other designs?

Better isn't the right term! HOWEVER, if you look at it in terms of potential, then I'll agree whole heartedly that air has huge potential as the aforementioned issues are ironed out. Exceptional adjustability would be nice. :-)

In my eyes, and for another 3 to 5 years yet, a hybrid approach (spring coil/air assist) is a better one. But for now, I'm still yet to ride a pure air fork front end that I trust to track well and remain compliant over the small stuff in fast corners.
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  • + 1
 Maybe it's time to give Trek and Fox some credit for developing the Dual Rate Control Valve (DRCV) it's one advantage that IMO defines the ride that only a Remedy can provide. My air shock has small bump compliance and mad traction. I'm interested in seeing the incorporation of this technology into their DH bikes in the future.
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  • + 1
 I currently run a cheap suntour fork with a coil spring(it's the 100mm fork) and I have not had any expierience with any other fork. However I think that for racing we will see more people moving towards the air sprung suspension as it's lighter and is getting better in feel. For the everyday downhiller however, the air sprung system might not be as great. P.S. I really like that Fox 40 RAD.
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  • + 1
 This says it all, Dungey, Stewart, Reed all returning to Coil Spring. Moto has the best suspension engineers in the world working on this and they still can not make it right !

www.vitalmx.com/videos/member/Chad-Reed-My-Way-Suspension-Testing-For-Monster-Energy-SX,8524/ocscottie,405
  • + 1
 The video in the article has chad reed saying he is sticking with the air fork.

at 2:20 he starts talking about the air fork and says, "I believe it has more positive than negative".
www.youtube.com/watch?feature=player_embedded&v=R0bxMRp6cLk
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  • + 1
 Quoting ML "One trait of an air spring that no amount of smart engineers locked together in a room can solve is their inherent rising rate."
This is not so difficult, they can make an air shock or fork feel more linear than a coil if they make the air chamber big enough. I did that on an old Judy fork and a sid shock back in the day.
That's why they have air can volume spacers now.
  • + 3
 For sure, they can make it more linear (DRCV for example). But I was talking more about the inherent properties of coil vs. air. No matter how big the air chamber is, the rate will rise.
  • + 1
 Yep, in an air chamber the pressure will rise on a curve, though the steep part of the curve can be engineered out if desired. I think a bigger challenge with both types of shocks is tailoring rebound damping to match the spring ramp, and air pressure curve.
  • + 1
 @mikelevy

...the general consensus on DRCV I have heard from too many riders, industry people and suspension tuners, is that Trek took good Fox suspension and ruined it with DRCV
  • + 2
 From a man who just bought a trek remedy 8 with DRCV front and back, you've just scared the shit out of me. personally, i've heard nothing but good things about DRCV. Furthermore, the design makes good sense to me, switching to a larger volume air chamber as the suspension gets more compressed should combat the rising rate quite nicely. Or at least delay it another few mm of travel. A slight offset is better than no offset I'm primarily a motocrosser, but while i'm at uni doing my Aerospace degree, i can't afford it. I dont think coils can ever totally be replaced thanks to the heating of air when its compressed repeatedly. Must admit, moving to air forks was a bit of a change, having to get used to never bottoming them out xD
  • + 1
 @foghorn1 And here comes the interesting part: no matter what part of the curve you take, if you zoom in its the same! If you adjust so the curve goes from bottom left to top right of the PV-graph, they'r all the same! There is no "linear part", the curve is the same EVERYWHERE, this is the formula, pressure and volume on the bike merely dictate what part of the curve you are using. Since that curve is pretty useless no matter what part you use, people have come up with systems so the overall behavior is more linear. Easiest is adding springs so the overall spring curve is more linear, such as the 'negative chamber' which is just another air spring acting in parallel.

Stating "the benefits of infinite spring rate adjustment" is also rather misleading since we are dealing with a curve, and an equally important part of that springrate-curve is controlled by the volume.

DRCV is a dual-rate air shock. At a specific point in travel the volume and thus spring curve abruptly changes (where it would otherwise start to get too progressive). I dont know, but if you cant feel that on the bike or its somehow not inconvenient, then Trek did one hell of a job.
  • + 1
 @mikelevy: It's funny how I had to scroll ALL the way down here to see anyone mention anything about the size of an air chambers' influence on rate. Does the fact that a MX fork OR rear shock are substantially larger than MTB have anything to do with their use in MX? Also to stir things up further; don't coil springs also have a rising rate? Slightly so anyway? Maybe a 10 foot long coil spring will cure the pesky rising rate.

Oh yeah, COILS RULE!
  • + 1
 Coil springs have an essentially linear rising rate. For example 400 lbs per inch of compression. Air springs have a rate that rises on a curve. The first inch of compression will have a smaller rate of resistance increase than the last inch. Hypothetically, lets say we set up a shock so that the first inch of travel ramps up 400 lbs. the next inch might ramp up 450 lbs and the last inch 550. This is because the volume of air in the cylinder and chamber get smaller as the piston moves in, causing the pressure to ramp up faster at the end. Increase the size of the air chamber, and the second inch might ramp up 425lbs, and the last one 510lbs. Increase it more and the you might get 400, 420, and 475...
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  • + 1
 Pump the forks and shocks up with nitrogen (and tires too for that matter) and you eliminate the temperature / pressure changes. The reason the pressure of "air" changes is due to the moisture content of everyday air pulled from the atmosphere. Plenty of commercial sources around for nitrogen tanks, and some are small enough to fit in your car trunk so you can haul them to races yourself. Its commonly used by among other things, the refridgeration and air-conditioning industries. They use the stuff to test pressure fittings and lines before filling with the coolant gases.
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  • + 1
 BMW Motorrad adjusts their coil shocks with magnetic oil system. Air is not so good for motorcycles, even with the most advanced technology and the apparent facilities that air system would provide for high performance motorcycles as S1000RR, R1200GS and K1600GT.
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  • + 1
 I have a tire shop very close to where i live, so they can fill my fork/shock with nitrogen as they do with some cars. For shock is a bit more tricky so i made an adaptor to fill my Fox DHX5 bottom out chamber to the proper pressure without losing gas when disconnecting the hose (suspension manifacturers should have that option). So next im gonna get an air fork when i have the chanceand im gonna put nitrogen in it too. So overheating negative effect solved, stiction wont hurt me much.
  • + 1
 can you really feel the difference? I am about to try it too
  • + 1
 Will test that in more details soon i hope. In theory nitrogen also expands, but differently than the atmospheric gas mix we all breathe.
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  • + 1
 My manitou circus Expert has air/coil hybrid. I love it for dirt jumping and i even rode it at whistler. being able to have the Coil+Damper+Rebound and also the ability to infinitely adjust stiffness with air is great! I like air hybrids like the RAD 40 because i will never have to worry about losing my fork in a race, i may lose air preassure but the fork will keep working!
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  • + 1
 I was a die hard coil rider for many years. Then when I tried a friends Roco TST air rear shock I wanted one. Now, for the last 4-5 years I have been on nothing but air front and back. No more coil for me, ahahhahahhahha RideOn!
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  • + 1
 I'm trying the CCDBA and a Dorado Pro on my Legend MK2 this year, so we'll see how it goes. You'd think 200lbs would be a nice round number that fork springs and frame rates would be able to accommodate, but I always seem to fall right in between rates. Its either over sprung and underdamped(good for smooth/jumping but harsh in the rough) or undersprung and overdamped(plush but dives in the steeps and lacks pop). Hopefully the infinite adjustability of the air will allow me to get it spot on. Plus when you factor in the cost of a ti spring, the CCDBA is actually a great value while still being lighter.
  • + 2
 Don't know how true it is, but I've always heard that the industry optimizes for an average weight of 180 Lbs, and a height of 5' 10". This is all sizing, not just suspension.
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  • + 1
 Mike Levy says, "but it is probably fair to say that the average supercross racer is far more demanding and in-tune with their suspension than most World Cup downhillers."

Errr, based on what exactly? This statement seems like highly suspicious assumption.
  • + 2
 That is based on talking to numerous top WC racers, the large majority of which not only seem largely unconcerned with settings so long as it is quite stiff, but also don't turn a dial once the season starts. I'm not trying to bash those riders - they do spend time testing in the pre-season, and likely know more about suspension than any of us - but much more emphasis is put on suspension in the moto world. More testing and far more resources.
  • + 1
 Well, you could be right, but those statements seem to contradict everything I've ever heard in pit interviews with WC riders and mechanics. I've never heard of a WC racer who wasn't dialing in their suspension relative to each course (not that I know each and every rider).

Further, it would seem, to me at least, that suspension settings are probably more important in DH than moto. Now, I'm sure moto fans will probably give me an earful for saying this, but, it seems to me that the variety of terrain from one DH course to the next varies much more than from one moto track to another. Therefore, track-specific tuning would seem to be actually more important in DH than moto.

So, if what you are saying is actually true about moto racers being more demanding than WC racers, maybe it's just a result of the fact that the moto teams have more resources and support, and can afford to be more demanding (read picky) about their suspension set up.
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  • + 1
 I used to always ride coil on my bikes and thought nothing could be better until I tried out an air fork on my DJ bike and loved it. I then took a chance and switched to a full air set up (front and rear) on my DH bike and I can honestly say I love it and will probably never go back to coil just because of how much you can fine tune it and how it's just as reliable
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  • + 1
 I use air shock on the rear all the time, nice to keep weight off the back... I'll admit. I have used air forks. And I love them the 36 talas are great forks. But I'm also a huge fan of the boxxers wc. Oil and coil are great... I think my preference on air is due to no oil mess when you blow a seal. Other than the weight factor. The mess is why I prefer them.
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  • + 2
 As much as I love the feel of coil spings (they just feel nicer in my view) I think air will take over once the tech is more reliable and refined as people like saving weight too much
  • + 6
 I find this a difficult area to agree, air shocks have certainly taken leaps and bounds forward in their ability to perform in recent years and the new CCDB air is no doubt a well developed and researched shock. I use the coil version of this for its tuneability.

But take a look around at the various areas of sport where suspension technology has progressed for decades and coils still rule, over a short race an air spring may stand up, if you are looking for reapeatability in performance during all types of conditions then a coil again rules, although as previously stated by others on here you can rapidly tune an air shock to different rider weights quickly and easily, so it has its advantages.

Bike designers would also have to look at their designs a lot more closely if only air shocks were available, this may rule out some of the great designs we all love and enjoy.

I say there is room for both and always will be, bike stuff seems to be trend driven, its purchased used and discarded when a new idea/application comes along, there are those of us who look carefuly at the product and purchase based on our research and time on similar products, may the choices continue, it drives the industry and design forward.
  • + 1
 i agree with you totally both have there place, just simply think people will be grabbed by the headlines of less weight and more tuneability and for racing where the parts are usually disposable and just there to get the best performance in that all important 4 minutes or so i think air may be seen alot more as its refined and made better. i know loads of people running boxxer world cups and love them but i personally love coil to much simply for its fit and forget factor as well as plush feel, maybe depends what the companies do and the riders they support. as often is the case the rest of us will follow the pros like sheep. i think a hybrid system could end up giving the best of both worlds tho.
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  • + 1
 My 2 cents: With all this talk of AMA SX, Chad Reed went from the new air forks back to coil for St Louis last week and had a better race than usual.

More importantly who can forget when this happened to Dungey's prototype air shock, putting him out of the heat race.
www.youtube.com/watch?v=U7WMwLQGPBQ
www.youtube.com/watch?v=phsjwY1hEo0

Air forks and shocks are a long way from offering as good performance as coil.
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  • + 2
 I rode 40's from 2005-2011, and now have 2012 air sprung boxxers they came on a demo 8, I was going to change them for 40's but after 1 year on air, there is no going back.
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  • + 2
 Chad Reed has been on the air forks all season in the SX, swapped back to coil for the last race and he rode the best he has all season.
Coincidence?
  • + 0
 he had his best season you say , not only last race
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  • + 1
 I understand the advantages of a air fork but I would rather trust a spring fork than an air fork, mainly because I defnatley know there is something in the fork unlike and air fork.
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  • + 0
 For a pro with unlimited spring choice options, the "slight" difference in feel with a coil might be an advantage. For the average rider, the ability to change spring rate as needed with just a pump is a huge bonus. Secondly, people get used to what they are familiar with. Around the year 2000, most top riders were still using 2 strokes, but as the new generation of riders came up, they learned their skills on 4 strokes. No one will ride a 2 stroke at the pro level now. There are a lot of reasons for this, but the downside the experienced 2 stroke riders felt with 4 strokes wasn't an issue with those who rode 4 strokes all of their career.
  • + 1
 With the AMA rule changes. You are no longer allowed to ride a two stoke in the top classes. The two stroke will make a come back. Now that they are starting to fuel inject them and can map the ECU. Time will tell though
  • + 0
 There are no rules that disallow 2 strokes. They just can't compete with the displacement disadvantage.
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  • + 1
 What about using Nitrogen instead of Air? I notice some car companies and off-road suspension companies using Nitrogen shocks. I wonder if that would eliminate some "issues" with the air system. Time to scour the web!
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  • + 1
 They talk about air on the Moto forks?
They don't use air in the forks, they are nitrogen charged so as not to be effected with temps.

Would this be the next step in the down hill forks?
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  • + 0
 Without a doubt as soon as the pros a coil are adapted to air technology, then the weight savings would make it nothing but an advantage. Still don't seem to understand why fox has been so behind with making there fox 40 an air fork. All the other manufacturers pulled it off without any issues. Who con complain about there boxxer wc? Plus with the ability to have provided the fox 36 float platform that I felt was very capable as a dh fork, you'd think your just around the corner.
  • + 1
 @summit800

the 36 Float is a great fork, but still not as capable as the 36 Vanilla when talking about more aggressive riding on rough terrain

the 36 Float never had the same small bump sensitivity as the 36 Vanilla, even when regularly given "lowers servicing", seal lubing, Kashima and SKF low-friction seals. It was really about the difference in the spring technology between air and coil. coil will always win when it comes to sheer sensitivity

I have owned too many Fox forks to know, unfortunately Wink
  • + 1
 Then explain why the boxxer wc and vivid air are successful and why rs hasn't stuck to coil forks?
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  • + 0
 "but it is probably fair to say that the average supercross racer is far more demanding and in-tune with their suspension than most World Cup downhillers." So an "average" moto racer is smarter and more tech savvy than our top-level athletes, what a compliment!
  • + 1
 I find that statement in the article so wrong it is offensive. Especially since the variance of shock speeds and amplitudes is very limited compared to downhill racing, less variance than motocross as well. Supercross is rather specific, which is why they can/try to get away with air sprung forks.
  • + 2
 FYI you have to be a pro to ride supercross. Although I'll agree that there has to be some major differenes between moto/mtb, I'll argue that moto would have more demanding loads put on it, not only due to the extra weight but the extra speed. Those supercross tracks can get rough too, maybe not DH course rough but nothing to scough about. And then there is outdoor motocross...
  • - 1
 DH has nothing on outdoor motocross in terms of suspension. I have raced both, and MX is the most demanding sport I have ever tried.
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  • + 1
 I don't know how many peeps will read this but Nirogen is air! Air has moister in it. Compressed Nitrgen does not. I believe all gases expand at about the same rate.
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  • + 1
 Maybe air fork tech will progress, but it doesn't mean that coil won't evolve too, into something way better than any air shock could get to.
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  • + 1
 i think air suspension will be like spd pedals itll be widely adopted in the race circuit but there will allways be the old faithfuls that will stick by their coils
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  • + 1
 Don't the pros whose sponsors ask them to ride an air fork just stick I coil in anyway when it suits. Just that no one would know.
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  • + 0
 Can't say I know much about air sprung forks. But I ran a Dhx Air 5.0 on my Sinister R9 for 2 years and it worked great. I'll probably buy another for my Glory when I can afford it.
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  • + 1
 I personally run my zokes 66 with no spring and more air. This was a night and day difference for me being a lighter rider. With the stock spring the ride was rough.
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  • + 1
 Nobel gasses for the pro forks? I heard a rumour that F1 tyres are filled with nitrogen so that temperature changes don't affect the pressures inside.
  • + 3
 They aren't filled with nitrogen so it doesn't effect the pressure, its so when the nitrogen does expand its gives an constant rate of expansion due to there only being one gas present. The new Nissian GTR has it from factory also!
  • - 2
 Aah that's interesting. A Noble gass could be used however as they don't expand with temperature (if what I remember from high school hasn't degraded with trauma over the years...). Bit more expensive, but maybe worth it if the sponsors are going so far as to label up coil forks as air to promote them.
  • + 7
 Noble gases do expand, everything expands when its heated due to an increased internal energy. What makes noble gases noble gases is they don't react with anything, they are also known as inert gases
  • + 2
 I +1 for nitrogen being the new route for fork and shocks. World cup races have all the mechanics they need to look after the bikes for the racers so by simply changing the air to nitrogen it wouldnt be anymore effort. Nitrogen in aircraft landing gears and wheels have been used for a long time due to the compressibility not being as high as air. It can also withstand huge temperature changes along with pressure changes. Just my 2 cent
  • + 1
 Then, my memory of nobles has definately deteriorated! It would be interesting to read an article about nitrogen charged air forks which gives some idea on changes to performance.
  • + 4
 1. You're both right, pure nitrogen does expand much less than air and that's one of the reasons for using it.
2. It's not just an F1 or GTR thing, nitrogen has been widely available to everyday drivers for years. Or maybe it's just in areas with high daily temperature amplitudes, especially at some times of the year. Anyway, it's not a problem to pump your tyres with nitrogen where I live. Apart from not changing its volume so much because of temperature, it also does not react with the rubber as oxygen in the air does, so theoretically should prolong the tyres' life. Although this might come useful only to those who don't drive too much and reach the tyres' expiration date (yes, they do have it) before they wear out.
  • + 2
 My rear shocks have run nitrogen for years. nothing new. People running nitrogen in new MX air forks for more consistent feel - but most people riding at a high level are switching back internals to convensional mechanical springs.

Don't think the tech is quite there for high end performance & the reliability / simplicity for privateers.
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  • + 3
 no selection for I am running air front and rear already??
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  • + 1
 i have the nukeproof scalp comp and my mate has the pro model and hes bike is always in the shop due to his forks
  • + 2
 But the forks on both are coil, yours are boxxer rc on the comp and r2c2 on the pro.
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  • + 1
 I think it's totally preference. For example, Cam Zink likes air shocks and forks, but others might not.
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  • + 2
 just give me the Fox already!
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  • + 1
 i change from air to ti coil an fast rooty race tracks. on classic german dh races i run air.
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  • + 1
 Iv been running air font and rear on my enduro for about a year and have had no issues
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  • + 2
 air is for tyres and springs are for forks..................
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  • + 1
 only for DH makes sense the coils... no doubt better for enduro, am makes no sense putting 1kg more on your bikes
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  • + 2
 I run air up front and coil in the back and it works just fine for me.
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  • + 1
 When the air builds up in a motocross fork, you bleed it out to get it to perfom correctly again.
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  • + 2
 I thought they used air all the time . Well you learn somthing everyday
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  • + 1
 Bye bye roco, hello vivid air r2c, best change I ever made to my dh bike (if i don't blow the vivid)
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  • - 3
 It'll definitely be something driven by both consumers and suspension companies - the more consumers that buy air forks, the more companies will slowly ditch coil models, further enforcing the choice and perhaps only offering the top end adjustments in their air models.
I'm very sad that there will be no more 160mm VAN 36s anymore, but hey in a few years it I can get the same performance at 500g+ lighter - why on earth not ?!
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  • + 1
 Air will rule DH in future. Just as carbon over aluminum. It will happen.
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  • + 0
 just swapped out my van for a 180 float. dayum.... makes a world of difference.
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  • + 1
 This may be a dumb question, but cant you develop a lighter spring coil?
  • + 1
 As in the coil itself you would be looking at TI or carbon (inhave only seen one carbon sprin though) and I have no few if it even went into production.

Even then though people will still strive to drop weight so I think skipping that and going straight to the air eliminates not only the middle steps but doesn't cost money in production ad testing. Never understood why fox only made the normal spring TI,
  • + 1
 That makes a lot of sense. Ive never ridden seriously with a coil suspension so I dont know all the benefits but I sure like my air shock and they keep getting better.. It just seemed that so many on this forum were boasting of the superiority of the coil over air. If its that good then I'm sure companies wouldnt mind spending more money on more R & D. Otherwise go for the air like you said.
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  • + 1
 Counter Measrue in Vivids? Does anyone have any more info on that?
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  • + 1
 Bos air forks are pretty dialed.
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  • + 1
 air supply is very nice
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  • + 0
 My marzocchi 66vf2 has both coil n air..so that make my fork bad ass?
  • + 1
 it is heavy and not reliable... just joking Big Grin
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  • + 1
 those 40's though
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