Tech Tuesday - What a Negative Spring is and Why it Makes the Coil-Spring Nearly Obsolete

May 22, 2012
by Richard Cunningham  
Today's Tech Tuesday breaks down a couple of doors that have been locked for decades. The first to go is the revered belief that a coil spring delivers head-and-shoulders better performance than an air spring. The advantage of a coil-spring is that it has a finite length at rest. In suspension terms that means, as the coil-sprung shock or fork extends to the end of its stroke, rebound damping begins to overpower the spring as it runs out of stored energy and comes to rest at a static state. This creates the butter-soft feel that once was the sole domain of a coil-over shock. A simple air-spring must be set at some static pressure in order to produce the proper ride height and that pressure is quite high (about 200 psi in the case of a shock). The air-sprung shock's rebound damping must fight that static pressure all the way to the end of the stroke, which, until the the invention of the negative spring, increased the amount of rebound resistance required and caused the shock to ride roughly.


Video: Air vs Coil Springs and why the Negative Spring is Important



Views: 31,397    Faves: 98    Comments: 7




Enter the Negative Spring

Suspension engineers discovered that placing an opposing spring that engaged at the end of the rebound stroke would fool an air-spring into acting like a coil type. In short, the negative spring counters the static pressure of the main air-spring as it reaches the end of its stroke and causes it to hover in place a small distance before full extension. Essentially, the air spring performs exactly like a coil spring at the beginning of the shock's (or fork's ) travel, giving it equal sensitivity over small bumps, and smoothness moving into the mid-stroke where the coil-spring once dominated. Fox and RockShox use an air negative spring, but a hybrid design using a coil spring to oppose the static pressure of the main air spring is used effectively by X-Fusion.


Simple air spring and how the negative spring works

This illustration depicts a simple air spring - a piston in a cylinder - to explain how a negative spring functions. (From left) Without a negative spring, 200 psi in the air canister forces the piston to the end of its stroke, hard against the travel limiter. The addition of a second air valve (center) below the piston, like the RockShox Dual-Air forks, equalizes pressure of the positive spring and suspends the piston slightly above the end-stroke limiter. As the positive air spring is compressed (right), the minimal volume of air in the negative spring quickly loses pressure and has no effect on the positive spring rate.




The boxing match is not over, however, because the coil spring is essentially linear. For instance: compress a 300-pound spring one inch and it stores 300 pounds. Compress it three inches and it stores 900 pounds. Simple math. Gasses, by nature, compress in a non-linear fashion. Left to its own devices, an air spring ramps up considerably near the end of its stroke. As it turns out, however, some degree of a rising rate spring is beneficial in both forks and shocks, and suspension engineers have learned to add or subtract air volume from the air spring to tune exactly the right spring rates for mountain bike suspensions. With the tables turned, suspension designers now use an end-stroke damping booster or add an air-spring in series with the coil (like Marzocchi's 55 and 888 forks) to emulate the air-spring's beneficial rising rate.


Fox Graphic Float RP23 cutaway

Fox Racing Shox provided this cut-away illustration of its Float RP23 shock. The air canister above the shock body replaces the coil spring of a standard damper. The negative spring sits just below the air-spring piston. Air pressure from the positive spring is fed to the negative spring through the air-volume sleeve via a tiny transfer hole near the bottom of the can. Every time the shock is compressed, the air piston passes the transfer hole and the negative air spring is recharged with the static pressure of the positive spring.




Coil-Spring Fails

Unless you are rich, the big fails for coil spring are cost and weight. The linear nature of a coil spring, and the fact that it derives its rate from a combination of coil-spacing and wire diameter, means that coil springs are only useful for a narrow range of rider weights and/or riding intensities, so you'll have to purchase a new spring to experiment with different preload and spring rates. Most riders use the spring that came on the shock - some are willing to buy one with a different rate, and darn few own more than two springs. An air-spring can be set to many rider weights and preferences - with a air pump. Last time I checked, air was a bit less expensive than coil springs sold by Fox and RockShox. Weight? Well you can figure that one out. Coil springs weigh between 400 and 600 grams (more than a dropper seatpost).


Fox Float Negative Spring Explained

In this simplified graphic, RC illustrates the function of the Fox Float RP23 negative spring.(From left) The negative spring is formed by the space between the main air piston and a seal at the lower end of the air can. An air sleeve surrounds the positive air spring. When the shock is compressed beyond a certain point, a pair of holes in the air-can (center) allow air to bypass the main air piston and fill the negative chamber. As the main air piston returns and passes the transfer hole (Right), it traps air in the negative chamber, and because the effective piston area of the negative chamber is smaller than the positive side, the air is compressed slightly. The activation zone (where the negative spring kicks in) is about one centimeter of the stroke, from the transfer hole, to the point where the negative spring equalizes with the positive spring.




Air-Spring Fails

Air springs have a couple of fails as well. Heat can expand the gas inside the spring canister and increase the spring rate midway through a ride. Most riders, even downhill racers rarely heat their shocks up enough to make this an issue. Perhaps in a 45-minute Super D situation, where a rider is using an under-sized XC air shock like the Fox RP23 for an extended super-techy descent would create a heat problem, but that said, it's a rare descent when an RP23 damper gets beyond warm to the touch. By nature, an air-sprung shock has more seals than a coil-over type, so starting friction is greater. Low-leverage suspension designs are susceptible to starting friction issues, as well as some fork designs. That said, super-slick coatings like the (dare I say the word?) Kashima treatment used by Fox have narrowed the disparity between coil and air-sprung suspension.

So, Coil-Over or Air-Sprung - Which is Best?

The bottom line, at least for mountain bikes, for the air-vs-coil-spring debate is that the performance gap between the two has been whittled down to nearly nothing by the invention of the negative spring and air canisters with variable volume. The versatility of an air spring simply kills a coil-over type. If you love coil-over shocks, by all means, ride one. If you want to save 400 grams and have the ability to change your suspension setup anytime you want for little or no cost, the modern air-sprung shock and fork is your first pick.


Did you find the Tech Tuesday information about coil and air springs useful?





Past Tech Tuesdays:
TT #1 - How to change a tube.
TT #2 - How to set up your SRAM rear derailleur
TT #3 - How to remove and install pedals
TT #4 - How To Bleed Your Avid Elixir Brakes
TT #5 - How To Check And Adjust Your Headset
TT #6 - How To Fix A Broken Chain
TT #7 - Tubeless Conversion
TT #8 - Chain Wear
TT #9 - SRAM Shift Cable Replacement
TT #10 - Removing And Installing a Headset
TT #11 - Chain Lube Explained
TT #12 - RockShox Totem and Lyric Mission Control Damper Mod
TT #13 - Shimano XT Crank and Bottom Bracket Installation
TT #14 - Straightening Your Derailleur Hanger
TT #15 - Setting Up Your Front Derailleur
TT #16 - Setting Up Your Cockpit
TT #17 - Suspension Basics
TT #18 - Adjusting The Fox DHX 5.0
TT #19 - Adjusting The RockShox BoXXer World Cup
TT #20 - Servicing Your Fox Float Shock
TT #21 - Wheel Truing Basics
TT #22 - Shimano Brake Pad Replacement
TT #23 - Shimano brake bleed
TT #24 - Fox Lower Leg Removal And Service
TT #25 - RockShox Motion Control Service
TT #26 - Avid BB7 Cable Disk Brake Setup
TT #27 - Manitou Dorado Fork Rebuild
TT #28 - Manitou Circus Fork Rebuild
TT #29 - MRP G2 SL Chain Guide Install
TT #30 - Cane Creek Angleset Installation
TT #31 - RockShox Maxle Lite DH
TT #32 - Find Your Tire Pressure Sweet Spot
TT #33 - Three Minute Bike Preflight Check
TT #34 - MRP XCG Install
TT #35 - Stem Choice and Cockpit Setup
TT #36 - Handlebars - How Wide Affects Your Ride
TT #37 - Repairing A Torn Tire
TT #38 - Coil spring swap
TT #39 - Trailside help: Broken Shift Cable
TT #40 - Installing a Fox Float Air-Volume Spacer
TT #41 - Replace the Seals on Your 2011 RockShox Boxxer World Cup Fork
TT #42 - Clean and Lubricate Your Fox F32 Dust Wiper Seals
TT #43 - Thread Locker Basics
TT #44 - Install a SRAM X.0 Two-By-Ten Crankset
TT #45 - VPP Suspension Bearing Service
TT #46 - Rotor Straightening
TT #47 - Finding and fixing that creak
TT #48 - Bleed and Service Magura Marta Disc Brakes
TT #49 - Cup and Cone Hub Basics
TT #50 - Install and Adjust Pedal Cleats
TT #51 - Cup and Cone Hub Rebuild
TT #52 - Converting Mavic Crossmax SX Axles
TT #53 - Cassette Removal and Installation
TT #54 - Cane Creek AngleSet Installation
TT #55 - American Classic Tubeless Conversion
TT #56 - Wider Rims Are Better and Why Tubeless Tires Burp Air
TT #57 - Pedal Pin Retrofit
TT #58 - Bleed RockShox Reverb Remote Lines
TT #59 - Cutting Carbon
TT #60 - Silence That Squeaky Disc Brake
TT #61 - Five Minute Wheel True
TT #62 - Removing Bike Rack Rattle
TT #63 - Inside Shimano's Shadow Plus Mech and How To Adjust It
TT #64 - Steerer tube length
TT #65 - Marzocchi 44 Rebuild
TT #66 - RockShox BoXXer TLC
TT #67 - Ghetto Tubeless Tire Inflator
TT # 68 - RockShox BoXXer Seal Replacement
TT #69 - Ghetto Dropper Post
TT #70 - FSA Orbit Option Install
TT #71 - How to Bleed Formula Disc Brakes
TT #72 - Crankbrothers Kronolog Cable Replacement
TT #73 - Three Ways to Save A Leaky Tubeless Tire
TT #74 - Chain Length Basics
TT #75 - Tech Tuesday: DH Helmet vs. Motocross Helmet
TT #76 - RockShox Vivid Air Tuning 2012




180 Comments

  • + 120
 had to switch the mattress back to coil, air was giving me a harsh ride.
  • + 22
 Pretty sure the new Coleman uses a negative air chamber, check it out! Plus, it's way lighter than a traditional coil mattress.
  • + 17
 All it takes is bottoming out a few times or for things to get rough and suddenly you're sleeping on a hot mattress. Nobody wants to sleep on a hot mattress.
  • + 16
 Tried water too, hydraulic damping spot on, but rebound poor, tends to give too much sag, back to coil too! Smile
  • - 5
flag santacruz-syndicate (May 22, 2012 at 9:03) (Below Threshold)
 i personally will stick with coil for now. at least on my dh bike. i tried air but im on the bigger side (6'4" 210) and i felt like the amount of psi i had to run comprimised the shock and made it feel choppy and rough. for now, ill stick to coil
  • + 5
 It depends on the application. I mean you save weight with the Air and sure while the coil might provide a more supple ride you just can't justify the added weight if you are deep in back country...

How could you debate this setup for a long ride Shark555?

At the end of the day you just want to make sure like cydaps says you don't have too much sag and that your properly sprung
  • + 2
 The only problem I have with air shocks and forks, is that in order for me to run it stiff enough to resist bottoming, I lose any form of small bump absorption. This is for a freeride and DH application though. For XC they have no equal...BUT, I also run all air on my dirtjump and slopestyle bikes, and the reason I love air so much on there, is the fact that it IS rock hard off the beginning with no small bump ability at all...If I understand it right, neg. springs get rid of this? This could be bad and good for me...Good for DJ, bad for FR and DH...hmm...
  • + 1
 My buddy and I did a few runs on the lift at Big Bear and the Fox RP2 on the rear of his Enduro was blazing hot! Wouldn't want an air shock on my DH bike when I'm riding even harder than on a AM bike. They're good for AM and XC though.
  • + 1
 I have a vivair and i fucking love it super supple and responsive and stays pretty consistent from my experiences with it....and i've had it for almost 2 seasons without any issues at all....I like but some people find it hard to shy away from the coil shock witch I can understand I just haven't noticed too much of a difference so it works for me!
  • + 2
 I agree.... I ran a Vivid 5.1 for a full season at whistler. No complaints.... even if suspension specialists say they are a 'junk' shock compared to the BOS Stoy or CCDB. I've now been running the vivid air for two seasons of full DH. Not on complaint at all..... I would easily choose this over the coil every time and if I had the money, I would be jumping straight onto the CCDB air. Weight plays a big part though. I'm not a big guy so I run a lot less PSI in the can too
  • + 34
 For downhill nothing beats the feel of a coil shock
  • + 22
 It depends. I have an air shock on my bike, and it has a fun and unique feel to it. Cornering feels more firm too. I like both coil and air, and I think this article has a very good point to it.
  • + 6
 I think, if you're going to have something top end like a CCDB air or a RS vivid air then they're probably just as good if not better than a coil, that said, I've not felt something as plush and responsive as my push tuned Van RC in a long time, wouldn't mind giving air a try though if I could afford it!
  • - 6
flag TyranT21 (May 22, 2012 at 4:40) (Below Threshold)
 If anyone isw orried about heat go to a tyre shop and get your shock filled with nitrogen. it will still heat up but not expand so the performance will not change at all
  • + 1
 heat issue not an issue? lol, i get my dhx 5 coil warm to the touch after any 2+min runs. same thing was for a friends rc4 on a scalp, if an air can is holding heat against it instead of letting it escape like a coil does surly its going to cause much bigger problems?

why do you think santa cruz went to a 3" stroke shock on the v10 after using a 2.75 for years? cos they were constantly blowing them up in the syndicate. with heat being a part of the problem.

air will work for xc but never dh racing, far too much depends on suspension remaining consistent.

as for people not changing coils? its the first thing every one i know does when they get new suspension, normally they just to a straight swap on coils for free. hardly a problem now is it.
  • + 9
 Sooo TyranT21 liquid nitrogen has the same volume as nitrogen at ambient temperature? The tire shop saw you coming! All gases expand as they heat up, particle size affects rate, scuba divers use argon in dry suits to slow heat loss, larger particle requires more time to covert heat energy into kinetic energy..!
  • + 14
 "normal" air is 78% nitrogen anyway.
  • - 5
flag kev-roberts (May 22, 2012 at 6:09) (Below Threshold)
 did anyone actually mention heat being a problem?

I never read the whole article, just a brief scan over.... Coil's aren't overly expensive to buy anyway and I do have 2, one on the bike and one as a spare which is a different weight...
  • + 8
 Agree with bxxer-rider, I ran a DHX air which would get hot enough to bake wet mud dry on the shock body on a 4 min run, on 10 min+ Alpine descents there is no doubt it was getting so hot that its performance was adversely affected.
Its a brave statement to say that a negative spring makes the coil spring nearly obsolete. This is only true where the overall weight of a bike is of more importance than the performance of the suspension.
When I see top flight Rally cars and MX bikes running coil free air suspension, I'll be ready to believe there is no compromise in performance.
  • - 10
flag northshorebmx (May 22, 2012 at 8:53) (Below Threshold)
 For DH and any aggressive freeriding for non Pro/Sponsored riders coil is the best bet. Cost is much lower and proven reliability. Let's get real, how many normal riders fine tune their shocks that often, I almost never touch my adjustments. Negative air shocks obviously have their place, shorter travel bikes for people who love to touch their adjustments and sponsored riders who don't pay for their bikes. Why does everything in mtb always have to get more expensive? The coolest man bike out with an air shock is the V10 carbon, most expensive bike ever, no one I know that has one payed retail, but SC sales tons of lame Blur's, Tallboy's and Nomad's with air shocks to lawyers and bankers. Pinkbike needs an exclusive DH/Freeride site to avoid confusing less experienced riders that just want to ride. If you want a great bike comparison check the bikes and prices of Santa Cruz to Intense, I'll let you decide which one is for your banker dad and which one is for someone who wants to shred everyday instead of working to pay for their bike. Don't overpay for the most high-tech bike on the market or you won't have time to ride it.
  • + 1
 He's not sating its the same volume he's simply saying pure nitrogen gas is slightly more stable when heated than air, which is true. The molecules of air we breath are of a different (smaller) shape and size than nitrogen. however I doubt it would have any noticeable effect on performance. Nitrogen definitely does have its place in the tire industry, but not for our everyday road cars. The only advantage to it in everyday tires is that it leaks out of the tires about 3 times slower than regular air, and it protects against oxidation of the inside of the tire (which is basically pointless because you still have regular air in contact with the outside. I agree with both of you, he was just trying to provide a simple solution, but as you said it rlly wouldnt make a difference. I bet some race team has tryed it over the years though.
  • + 1
 @bxxrrider, i doubt they switched to the longer stroke b/c of the shocks blowing up. newer generation bikes lowered their leverage ratios making 3" stroke shocks more practical.
  • + 2
 different gases, molecular size, temperature and pressure.... herd of Mr Avogadro?? you're off the mark with air vs nitrogen, back to the books gents
  • + 3
 if it really was better you would see top DH riders on air not coil because of the performance advantage, but this is not the case
  • + 3
 Yes I realise that everything expands when it heat up and that air is 78% nitrogen but its the moisture in the air that expands the quickest as it heats up. I was talking to someone who was a mechanic for suspension on moto gp bikes and thought the same as you guys in that it all expands anyway but he was saying that its the water in the air that is the problem and thats why they all use nitrogen in high performance things. It would make a much bigger difference in the motorsport industry as teh suspension works so much faster then on a mountain bike. And just for intrest he also made titanium fork legs on his own lathe for trials, really cool to see.
  • + 3
 dear SRAM, just give Vivid air to SamHill, let he take the 1st spot dear FOX, just give 'air thing' to Gwin, let he take the 1st spot
  • + 1
 Tyran that sounds quite interesting about the water vapour in the air, I should try dry compressed air and see if that helps.......
  • + 5
 Avogadro... that's the dude who invented guacamole
  • - 1
 I read some of the dumbest comments on pinkbike, you guys gotta go and ride sometime. Nitrogen, cmon. Anyone who cares about that probably rides a road bike in spandex. Good to know I'll never see you on my trails.
  • + 1
 Yess, because road bikes have suspension and all.
  • + 14
 For me an issue with air springs is not harshness - it is their tendency to dive into the mid travel, you need both less SAG and more LSC to make them similar to coil. I'm more than fine with that on the shock but with forks - mnaaaeh, dunno - MZ RC3 Ti makes it click for me with only 200g of weight penalty over Revelation or Float.

Does anyone know if companies give different compression/rebound tunes depending on spring type?
  • + 5
 i know that mz does..u can buy different shim stacks from them..dunno about the others
  • + 1
 Yeah i totally agree. Its like like the sag is way too loose but after that its all good, rebound can be an issue but this article seems to explain why thats no longer an issue. So much jargon here but it seems to make sense. Wish i had the cash to try both out.
  • + 7
 I have a bike that I switch between a RP23 air and a DHX 5 Coil depending on the day ahead of me. I really like the RP23 more for trail riding and not just due to weight. It just has a really good feel at slower speeds, which are typical in the tight woods of the northeast. I get a really good pop off lips when I preload, and corning at mid-speed also feels great with the RP23. However, if this bike goes to a lift access situation with long downhills, lots of high speed breaking bumps, bigger hits, etc - the DHX 5 goes on the bike. I was skeptical of air systems for years, but have really grown to love the feel of a quality shock like the RP23 for day-to-day trail riding. I also just recently switch from a coil fork to a X-Fusion Vengeance air fork and have been very happy with that. Old habits die hard, but the air technology now has come along way.
  • + 1
 I can see the advantages of air over shadowing coil but I don't believe it is fair to say that coil should die completely, even if in the future coil will be a treat for conneseurs, coming mostly in ti version. It is a bit like with semi- and open bath damping. Semi will always be lighter providing only slightly harsher performance but still, open bath has it's sweet cream topping taste. Maybe some companies will specialize in manufacturing coil spring kit replacements for various forks. Air is great for manufacturers, great for majority of users - it is a very socialist idea Smile
  • + 1
 I agree with WAKI. The best would be that both coil and air shocks stay on the market, because it's all down to personal preference. Both systems are great, air shocks are more reliable than they were 7 years ago, both has their pros and cons so one can't say for either (coil or air) one that they are bad.
  • + 5
 I think it's worth remembering that the leverage ratio of a particular frame will also influence the sag/ mid-stroke/ progressive performance of a given shock.
  • + 1
 Well for me it is mostly about the stiction with air dampers: They need a lot of breaking in due to the many seals and still after some time they have way too much starting friction. Though I see this problem more with the forks than with latest set of rear dampers available.
  • + 2
 Well trickn0l0gy that is because as stated by RC a rear shock has leverage on it, a fork is worse than even 1:1 because of headangle.

But other than that, if you want less dive and have a fork at less than its max travel, make the negative air chamber smaller by putting the largest diameter custom spacer you can get. I have a Reba lowered to 50mm for street- the air spring feels awful. In fact, it never even gets progressive, it is stuck in the digressive part of the stroke because of the ratio of the size of the negative chamber to the positive chamber. Customizing the size of the negative chamber is one more way to tune your ride.
  • + 1
 As far as my logic goes, the leverage ratio alone has nothing to do with either linear or progressive characteristics of spring medium. It just makes you need to use more/less air pressure isn't it? Sure, that will make it slightly more progressive but to my understanding it is the changing leverage ratio and frame rate (like VPP) that does make a big difference.

If I'm wrong please explain.
  • + 1
 @WAKIdesigns, you mention leverage ratio and frame rate in your comment, can you distinguish between the two?

As far as I am aware, a frame's leverage ratio imparts a force on the shock (spring) for a given rear axle movement. The shock (spring) will provide a resistance to the applied force. The combination of the frame leverage ratio and shock resistance characteristics give the wheel rate - which is essentially how the bike will 'feel' under compression through the stroke. Some bikes have a progressively stiffer resistance (bottomless travel), whilst others may be more compliant mid-stroke.

Frame leverage ratios can be linear or non-linear, therefore applying a different force onto the shock through the stroke. Most bikes tend to have a linear progressive rate these days. A traditional coil spring has a linear resistance (Hookes Law), as RC explained in the video. Air shocks (springs) have traditionally had a non-linear, exponential resistance, i.e. the rate of resistance increases the more load that is applied.

So, if you combine a coil shock (linear) with a linear leverage ratio frame you'll get a linear progressive wheel rate.
If you combine a coil shock (linear) with a non-linear leverage ratio frame you'll get a non-linear wheel rate.
Etc...

That's my understanding - hope it makes sense!? ;+)
  • + 14
 I literally lol'd at the title... The negative air spring isn't even close to making the coil obsolete and air shocks still have some VERY large shortcomings they need to address before that will ever be a possibility.
  • + 11
 Engineer in me gets annoyed about you describing energy in terms of lbs, that's a weight, which is a force induced by gravity Razz
  • + 0
 winner
  • + 1
 Weight is not a force induced by only gravity. Although I agree with you how annoying it is to hear lbs instead of in-lbs for energy.
  • + 0
 Weight is a force and gravity is the only thing that induces it. You're probably thinking of mass
  • + 0
 Nobody knows, what mass is. To check one theory they build LHC in Europe and other did experiment more then 1 year in Fermi-lab.
  • + 0
 lol at Bowen, couldn't be more wrong. Weight is the force gravity puts on an object... that is literally the definition.
  • + 2
 What he means is that lbs can be used to define any force, not just weight, which is true.
  • + 8
 YAY tech tuesday video ! yay Richard Cunningham ! i've missed this a lot. and this was very interesting aswell ! i don't mind weight and although i don't ride very hard and an air shock would do the job, i'd rather stick to coil spring. i like it's look and feel.
  • + 5
 "If you want to save 400 grams......"

I can save double that by taking a dump before I ride. I'm very happy with my 'obsolete' coil fork mainly because I doubt I could get anything near as reliable or smooth in an air fork in my price range (think £200/$300ish). I'm sure that a super kashima coated uber air fork/shock is fantastic if you can afford one. But for me I just want something simple that works reliably....and air suspension is anything but simple.
  • + 2
 Actually, they are pretty much the same. The only difference is in the spring. And although you have a good point in low cost/reliability, you are not right if you think that it's the same if your bike is lighter by 400g or you are lighter by 400g. Maybe you can't feel it, but there is a difference.
  • + 1
 That comment was (slightly) tongue in cheek Big Grin . I'll grant that 400 grams is a much better weight saving than that ridiculous carbon air shock that was on a while ago (15 grams saving...) and at least its sprung weight so it will make more of a difference. I'm just one of those riders that pretty much shuts down if someone starts trying to sell me a part by first banging on about the weight reduction. As I said if I had the money I'd be rocking a full suss with air at both ends. As it is my coil sprung hardtail keeps me going...well actually the forks are away getting serviced since the rebound failed...so much for coil being more reliable eh.
  • + 1
 Well it's not the coil or the seals that's broken, it's the rebound cartridge? Big Grin

In my opinion, 15 grams is only important when you are a pro racer... and for people who brag with their bikes, not their riding.
  • + 3
 @Richard Cunningham: Loved the Tech Tuesday - absolutely brilliant. I do have a question which maybe you could answer? I understand the theory about the coil spring returning to a static position at the end of the rebound stroke, however what happens if you've applied pre-load to the coil? Surely then you have stored energy in the coil spring at the end of the stroke?
Keep up the good work!!
  • + 1
 The shock cannot extend more than it's full travel. Say for a 57mm travel coil shock, even if you preload the shit out of your coil, it won't become a 60mm travel shock. It is set internally that this particular shock will have an overall length of 200mm and an available travel of 57mm (most 57mm shocks are 200mm in eye to eye length). The Preload is just a way of "cheating" to get the right SAG ^^

That also applies when you lower a fork, you clip to the rod, next to the negative spring some internal travel spacers to prevent the forks from getting its original full travel back.

I hope that answered Wink
  • + 2
 If anyone thinks their air shocked Nomad rides as smooth and plush as my RC4 coiled/push linked Nomad, lets do a swap for 5 minutes. There is no substitute for coil without some kind of compromise in performance, and with a Ti spring I'll take the 200g penalty. Same goes for my 55 RC3 Ti. I've yet to feel a similar travel fork that can compare in small bump sensitivity, with amazing bottom resistance at the same time. Some things are worth carry a little extra weight for. Suspension and tires affect your ride more than anything, so why cut corners there to save an amount of weight you will barely notice?
  • + 2
 Never thought I'd admit to it, but I'm preferring air to coil at the moment. Got a Cane Creek DBAir and after hours of trying to set it up correct, it's just about perfect now. Smoothest ride ever on my TR250, it's lighter, more responsive and I can easily change the spring rate for different terrain. Tends to be a bit hard still towards the end of the stroke, but just removed to high speed compression and have nearly fully travel now. I definitely feel that riding the same terrain with the DBAir compared to the Fox DHX4 with steel spring before I have a more responsive rear wheel, and I feel more in control of the bike.
  • + 1
 I totally agree! I have made the same experience with the DBAir on my Slayer.
  • + 2
 I think X-fusion, Vivid Air and Cane Creek Double barrel Air have it right. Who cares about pedal platform and a small window of rebound adjustment, I want true compression and rebound adjustment. The only reason I love my Enduro Evo with RC2 Fox shock is because I can truly tune it, that is way more valuable than being able to adjust the spring/ air pressure, especially once you get the right spring on it. It is way easier to change a $25 spring than it is to get a RP23 shim stack adjusted or PUSHED.
  • + 1
 Yeah, was soooo glad the DBAir didn't bother with any pedal platform, the shock feels buttery smooth without all that stuff trying to reduce pedal bob! Smile
  • + 2
 But what if your bigger like over 200lbs? I don't know if that air shock would do it for a man of my size. I think they need to do a Tech Tuesday for bike set up for Big Boys. It has been hard for me to find set-ups shock settings, tire pressure for my down hill bike (the jump bike I run the fork at 100 and the tires at 60-80 psi works awesome lol) most of this stuff is for a 140-180 pound rider well big boys need help too.
  • + 1
 Exactly my problem my rp32 is at like 280+ psi i weigh about 240lbs, same for my tires 60+ or they just don't work! it all gets very frustrating haha
  • + 1
 so then run a coil?? and yeah the tire pressure thing really sucks
  • + 3
 @Banders Switch to ghetto tubless, use 20" tubes as rim strips on existing rims, pick a tire without a super stiff sidewall (all Maxxis work great), pour in your stans. Done and Done. I'm over 200lbs. I've used this for years DH, 4x, Freeriding. Low air pressure, no flats, great performance. Message me if you have questions.
  • + 1
 @northshorebmx it's the truth! I run my Minions at 30PSI for downhill, and I weigh in at 230lbs with gear.

@The-Banders the newer Rockshox stuff has set-up guides available on the SRAM website. I just use my weight and dial in the settings according to the charts to get a good starting point. Every fork and shock should come with something like this as far as I am concerned!
  • + 1
 Yeah. I have a boxxer up front and a cane creek double barrel in the rear on my legend the bike is new so I'm just starting to figure things out. On my amp I just pump the xfusion up to 100psi and that works well.
  • + 1
 Banders for us big boys pump that rear shock to 180-200, for tire pressure on a downhill rig i always run less, usually 35-40, want my tires to grip, as for the rear I have a rc4 with a 600 lb ti spring seems legit enough
  • + 1
 600lb ti-spring holy crap. mine is a 450 but I just got a DH bike so it's still getting set-up.
  • + 1
 Yeah dude 600 is prime, I was shocked to see it came with my sx trail when I bought it, works great though
  • + 2
 Don't know about shocks since I have a hardtail, but I installed dual air fork last year and will NEVER go back to spring forks. Negative + positive chambers give you SO MUCH control, that I already forgot about compression and rebound settings. You can do whatever you want with just one fork and one pump. Just a few strokes of pump into right chamber and you go from ultra plush extra linear fork for commuting to stiff and progressive one for dirt jumping.
  • + 1
 Exactly.
  • + 2
 What? The word "durability" not in the article or any of the comments?

Coil and air both have advantages and disadvantages. One of the biggest advantages of coil/oil suspension is durability. Durability as in a coil and oil shock or fork can last years with zero maintenance. Bike fanatics wouldn't do this but the vast majority of riders aren't bike fanatics.
  • + 1
 totaly, i wanna be riding my bike not adjusting,repairing, servicing it, i pretty much tweak my vivid coil then just adjust the compression knob for how fast/hard im riding
  • + 5
 nice job RC right to the point. wondered how the air shocks "stuck down" very informative!
  • + 1
 If performance is the same - why don't we see the use of air shocks in mx, Moto GP or off road racing? Heat can be managed easily through cooling systems and larger air volumes so that can't be it. In those sports where weight is critical, wouldn't air have become the spring of years ago if it was viable ?
  • + 0
 Good point. I can see the advantages for XC, but in the aggressive sports industry Coil is still king. RC would never run an air shock, neither would James Stewart, Napalm, Casey Stoner, or TheDoctor. For DH, coil shocks are for men, air shocks are for weight weenies. Air is marketing hype, coil is necessary for high speed chaos and aggression. For alot of action sports athletes, the big advantage of coil is that it improves your traction, because the tires stay on the ground better. Negative air springs have been used with mountain bikes ever since the Rock Shox Mag 21 about 20 years ago. The same claims were made back then, and while they have been improved, so has coil technology, so I don't think it's fair to say that air springs are closing the gap.
  • + 1
 All the pro MX riders you are name-dropping would in fact ride whatever-the-hell their sponsors paid them to ride. This is the very essence of pro anything and factory racing teams. The "aggressive sports" you are talking about clearly includes motocross, which has weight minimums, which were set to accommodate heavy-ass four-stroke bikes with coil suspension. This limits any incentive to adopt and advance air suspension for motos. Ricky Carmichael would _never_... he a close confidant of yours? Get a grip, man.
BTW, you might be surprised by all the unaggressive sports for which Fox makes air suspension, their website is only clicks away.
  • + 1
 Idk my experience with an air shock on a dh bike was, at the proper pressure it sat way too low, blew through the travel, and was harsh off the top, if i increased the air pressure so it rode at the proper height it still blew through the travel and was WAY too harsh off the top, of course i could have re-valved it and i might have got it close but that takes a lot of time, testing, know how and MONEY. People need to stop worrying how light there bike is and worry about getting it setup properly, I cant believe people are too cheap to look around and get the proper springs for their bikes.
  • + 1
 This is a pretty cool article, definitely worth reading, and very interesting.

But I gotta know...Do those guys who go out and just rip, and you all have the friends I am talking about, really spend time thinking about stuff that is this tech? Perhaps... but my guess is they are too busy riding to worry about it.
  • + 1
 the negative air sring is nothing new in any terms.....but its one hell of a marketing ploy for the bike companies to use.
most mountain bikers may not be engineers and therefore their knowledge of such things limited to the sport of mountain biking.

but the air spring will never make the coil over obsolete....what a stupid thing to even concider implying!

the matter of fact is unless your pro and every little gram counts in a race then to the rest of us it doesnt matter.

ok there are your weight weenies and bike tarts that MUST have what is marketed as the BEST shock ever, wether it makes a difference in their riding or not.

how many of you guys have been out on your bike (not top of the range) and seen other guys with TOP OF THE RANGE bikes and shocks and body armour and jerseys then been astounded at how badly they ride?

it really only comes down to the user.

plus the reliability and cost of a coil over seems to far out weigh the cost and reliability of an air shock.
  • + 1
 Yeah, another overly simplified article from RC, that leaves out large bits of nessescary information and any form if counter point... I see you're going back to your preachy "magazine" writing style RC... knew you couldn't stay away for long. Both have their place and both have their drawbacks. Its just too bad RC has never been out much if a "gravity" guy or he might get that. WTF is he doing writing here anyways???
  • + 1
 Oh, and the poll at the end of the article should be removed or done properly. The options are so poorly written that absolutely no meaning can be gleaned from tallied answers. Attempting to derive meaning from such a badly structured poll will actually lead to a worse understanding of the opinions of those being polled. Seriously, the poll sucks.
  • + 1
 lol you can vote for all four options and call it good Big Grin
  • + 1
 Coil shocks are also a little bit effected by generated heat. On some shocks the piggyback is pressurized with x amount of air so if that amount of air heats up it increases its pressure. The amount of increased pressure doesn't effect it as much as an air shock, but it is is still there. So what can we do about it? Depressurize the piggyback, compress the shock to full travel and then pressurize it with Nitrogen. Would it make any difference? Oh and very nice Tech-Tuesday!
  • + 2
 Air shocks, event hose with neg/pos chambers will never achieve the same plush feel as a coil spring shock, this has probably already been said, but worth saying again. They can get close but will not be the same.
  • + 2
 lol i voted for all four of the options in the poll Big Grin i dont think you are supposed to be able to do that. The video was very informative. i have always wondered about the diferances between coil and air.
  • + 1
 I run air both front and rear (MZ888 ATA WC and MANITOU evolver ISX-6) on my gambler and i am in heaven! I had to send my shock to a mechanic to get it more progressive, in order to get sensitivity on small bumps without bottoming on the big ones, and now it's just perfect, butter smooth! and the fork, well, it's just brilliant, go slow and it is kinda harsh on the small stuff, speed up and it floats trhough anything! (i run maximum low-speed compression and minimum high-speed) it's just great without too much brake dive and unnecessary suspension action on slow terrain while opening up on the fast and rough stuff. I'm totaly sold...AIR FOR ME!!
  • + 1
 one thing not covered where the advantage goes to coil is maintenance. Fox recommends servicing the air sleeve every 30 hours. For a lot of guys, that's too much. The difference between a dhx and a ccdb air for a 2.25 X 7.875 rear shock is around half a pound - "big deal"...
  • + 1
 the only problem of the dual air is leakege the negative air spring but that is because people don't service their forks-shocks i like the air or coil but i ride the coil because there is less maintenence (i am a slob for maintaining forks and shocks)
  • + 1
 There are a number of incorrect statements made in this article. The main one is this: "the air spring performs exactly like a coil spring at the beginning of the shock's (or fork's ) travel, giving it equal sensitivity over small bumps". If you consider how a positive and negative air spring works, the reason the suspension will sit at full extension is because of the surface area differential between the upper and lower side of the air piston. The pressure on the upper side has a greater surface area to act on, and for this reason there will always be a certain amount of air preload force acting on the fork to hold it at full travel; thus producing a degree of harshness at the start of the stroke compared to a coil sprung equivalent.
  • + 1
 Excellent topic, very informative and good video. However allow me to offer my different perspective which is that air shocks more than air forks are way behind coil shocks from A. a design and construction perspective and B. by personal testing.

A. Compared to the lower pressures required for a fork the high pressures of a shock require much tighter seals and higher friction on the shaft and the protruding stanction. One can argue about the Kashima or special oils with friction additives like I ve used in air Totems with success. I ve tested an Intense tracer with Kashima shock and one without and could not notice a difference either when pedaling or on the trail. On a 36 fork I think I could, but also note that the non kashima was well prepared for a ride.
Negative and Positive piston area ratio create a slope of the force as the shock compresses and it would be nice for the manufacturers to post that as well the spring rate so we can choose accordingly.
So what existed before the negative chamber? was there vacuum or was there a rubber bump or just a hole?
Unless you try a bike and continuously bunny hop and feel the extension of the suspension , on the trail you are always somewhat compressed and the feel there is what is more important, not how it feels when you drop the bike in a LBS.
Agreed that the weight difference for a trail bike is considerable with a steel spring.
Regarding tunability, the negative pressure is dependent on the positive pressure so back to the fixed ratio. Scott with their equaliser shock had separate adjustment for positive and negative pressures as does the new Cannondale. Read some reviews about them and the riders comments about small bump compliance. Forks generally have pos and neg adjustments so are more tunable.
  • + 3
 B. Personal testing.
I have a Tracer 2 on which I changed the rp23 to RC4. The bike was a joy to ride but with the rc4 it can do everything. You could go to maximum sag with the pr23 and for example go relatively comfortably on a rocky trail but then forget any drop more than 4-5 ft. One could argue using a DHX air with bottom out compression but this shock has even less mid stroke support.( the ratio we talked before)
Going to the lesser sag ( within allowance) , meaning higher pressure on the rp 23 led to stiff bike feeling it has less travel. For example I ride a Tazer vp with minimal sag and on drops the two bikes did not feel far apart.
The tracer with the rc4 is simply amazing. You can blast trough any trail or dh track which indeed is not what it is supposed for, with comfort and surefooting.
Indeed the rc4 is heavier, but one can also bump up the pressure in the rear tire which reduces its friction and makes for a faster bike balancing some of the weight handicap.
  • + 1
 I'm agree for the equaliser shock and cannondale fox dyad rt2... I own a Jekyll and the felling of the rear shock Yes it have smal bumb compliance and I really like the fact to adjust the 2 chambers pressure individually it allow you to get more personalised settings than my previous rp23 from my old bike. sorry for my english I'm not bilingual!
  • + 1
 with the issues of air shocks over heating you could just put a buffer zone just inside the external wall of the shock with a cooling fluid inside to help disapate the heat that causes air shock to become inconsistent and/or fail im 13 and able to figure this out. come on the guys at rock shox foz marrizochi ecxt. couldnt figure this out? it would ad about 20 to 30 grams to the air shock also for heavy riders theres always the piggy back system also as for adjustability for push shocks ad more chambers that you can lock off to increase or decrease travel like a pull shock. peaple should think more and there would be so many question tho i understand as it took me about 5 days of studying air system and spring systems to understand the concept of both i prefer air systems i jump my local trails and hit 5 to 6 foot drops with my air shock often and have no issues i run around 80 psi on my rear tire and 75 on my front and 150 on my shock and i cant remember the pressure on my fork and i get both small bump complience and can still hit hard on the landings so i dont see the problem of them
  • + 2
 I do love the feel of my roco wc coil on my DH bike but air shocks are definitely more versatile, it would suck to blow a seal on a air shock while riding tho...and it'd be pretty hard to break a spring haha
  • + 1
 I blew a seal on my fork last ride, the last section of the trail was really bumpy. Yes it sucks
  • + 1
 wow that would be horrible, the worst ive had is to blow the valve stem seal and it had a super slow leak. I couldnt add any more air or it would strip my shock pump(kinda confusing?) so i was stuck running like 50 psi haha
  • + 1
 fantaman if you read the article, it would explain how that is not necessarily true. i have been on a vivid air and an elka stage 5 this season, the vivid performed just as well if not better then the elka. with the newer technology these days, air shocks are just gonna keep getting better and better.
  • + 1
 easy to choose... downhill is going to really work the shock so its best to use coil ... xc ix not going to work a shock so much so a shorter travel bikes don't need the heat resistance of a coil spring. its the mid ground that gets confusing between 140 and 170mm travel, a lighter rider will not run as higher pressure so the shock wont have as much compressed air friction in the air chamber this means that it will heat up less and therefore they will not need a coil spring on a longer travel bike, a heavy rider will need more air pressure which will cause more heat build up so they might see the need for a coil shock on a shorter travel bike the biggest factor though is rider aggression, a more aggressive rider will put a shock through more work and so may need a coil shock over a lighter or smoother rider who will find they don't push a shock as much.. allowing them to reap the weight advantage of air without really loosing performance...

on forks its much the same but is less significant because lower pressure
1>the leverage ratio is 1:1 meaning significantly lower pressure is used
2> as stanction size increases the volume increases allowing lower pressures to be used
3> much larger surface area allows heat to be dissipated more efficiently
lower pressure reduces heat build up and so is better for air really its as simple as that really
this means that where a rear shock might need to be a coil at 160mm of travel you may be able to use an air fork for a 180mm bike without any problems
  • + 1
 A balanced informative article on a real topic debated by many cyclists Eek i am still on pinkbike right..

Really enjoyed this article, more like it please pinkbike. I'll still most likely always be coil, purely from a reliability standpoint, but educating people is always good!
  • + 1
 I have heard talk of "Hammock" effect on air shocks,(weak mid-stroke I believe)
Think this why Fox added the "Boost Valve" to some of their air shocks,
anybody know about this?
  • + 0
 3 years back I tested a DHX air on a specialized Big hit, the older model. It absolutely minimized pedal bobbing, behaved actually quite well in jumps and drops but this frame had a rising rate suspension making it very progressive, but on a rocky trail or rock garden you thought you had 5-6 inches of travel and the tires not glued to the ground like the cheaper van rc coil shock. A SC nomad in a German magazine was test winner with a coil shock in one year and almost last with an air shock a year later, had the not been a sigle pivot bike with an air shock. So I d think that an air shock is preferable for trail bikes up to 100mm travel, like the bike on the second part of the video. An air shock could possibly be acceptable by a world champion in a particular track, but on an all mountain bike, the joy, quality, smoothness of operation of the suspension with a coil shock and tunability with different spring rates and preload , can help tune any bike with any leverage type to the requirements of its rider.
  • + 3
 Some good points you made there. My opinion is that it's down to personal preference and riding style.
  • + 0
 All I can say is I've seen way to many air shocks blown at Highlands. Until someone can make an air shock thats lasts I will go with coil. Compressed air has more density and creates more heat. That causes failure at the seals.
  • + 1
 I don't know about you guys but I love my ti coil over air. You tend to loose a bit of air after some ride and the shock don't function that well after you loose it. IMHO coil feels plusher when I do DH.
  • + 1
 Not sure if this is any of the other comment but what about for larger riders over 200lbs. I have heard in the past that the high levels of pressure required to for larger guys cause issues with the shock.
  • + 1
 My DRCV gets smoking hot and definitely changes feel significantly every time I go ride. If you ride in a place where every ride is an enduro run that happens. Pisgah destroys air shocks.
  • + 1
 Just by a zocchi 44/55/66/888 rc3 and you`ll have both a coil and an air spring, and adjust air pressures and adjust oil volumes to alter the rate and/or the progressiveness. Versatility and longevity.
  • + 1
 fox coil DHX 4.0 all day Helmet long riding days on the mtn will crush an air shock if u ride real hard. i like coils if i had the money i might run a air shock on my race bike....maby..... nice video guysSalute
  • + 1
 Awesome video...really nice explained the stuff !! Airshox are the way ...ridin for 4 years now nothing else and Iam close to 220lbs Wink
  • + 2
 Very good Tech Tuesday. This was very informative and enjoyable to read and watch.
  • + 1
 Performance is one thing, but reliability is quite another. I think coil is more reliable as there are less moving parts. I'll be saving for a Ti spring.
  • + 2
 I like RC's tech tips so much better than his bike reviews. Without the sales / booster mentality his writing improves.
  • + 1
 I've been using a fox 180 talas which has been brilliant both in 140 and 180 mode.

Waiting on a CCDB air and i'm hoping that "air is the new coil"
  • + 1
 You won't be disappointed with the DBAir mate, got on my one TR250 and now it's set up (too bloody ages) it's beautiful. Sooooo plush and so much rear wheel control. Definitely a more confident rider now, tracks the ground beautifully.
  • + 2
 title is missleading this is aimed at xc/trail riders,not DH/park riding.
  • + 0
 The tech applies to every shock, xc DH or automotive. The opinions are debateable but that is the nature of opinions. I personally race super d and prefer an air shock for being able to up the pressure for pedally stuff. Also, as DH weights come down air becomes more sensible.
  • + 1
 theres is a reason why most wc riders still run a coil. Dh is brutal air shocks dont hold up as well
  • + 1
 true reliability will always be the winner in the end for non-pro DH riders who need their stuff to last.
  • + 1
 even with pro riders a lot rode vivid air when they were prototypes but now a lot are back on the coil.
  • + 1
 This was a brilliant tech tuesday, explained a perhaps confusing buzz-term in a really straightforward way.
  • + 1
 Weird, i actually watched over half of an hd video with it not having to stop to buffer, on a mac....
  • + 1
 well now i know why my totem single air sucks so much compared to my fox 36
  • + 3
 It's only Monday :o
  • + 1
 I wanna go hard.
  • + 3
 Depends where you are.
  • + 1
 Really? You don't say... Tell me more?
  • + 1
 excellent note! I enjoy using spring coils in my DH bike whilst for Trail/AM/XC I love the air ones.
  • + 1
 What about ti springs?
Also, does elevation effect air sprung shocks? (8000' vs sea level for example).
  • + 1
 nah cos it's a sealed unit pressures remain constant, external temp might make some difference but the internal pressure is so high that this will probably be negligible (will be quite cool anyway as the molecule's kinetic energy is restricted by the pressure like in an aerosol can)
  • + 2
 What about ti springs? It's just a different material.
Elevation does not make a difference since the shock is an isolated system.
  • + 0
 Elevation causes relative pressure inside the shock to increase marginally I think. It shouldn't be enough to greatly effect your ride though.
  • + 2
 Relative pressure doesn't have anything to do with it. Pressure inside stays the same, shock works the same.
  • + 0
 take it to the bottom of the ocean and it will compress more and more easily the deeper you go. (sharky boys should no that. . .) In the air the effect is too small to notice, but it is there.
  • + 1
 know*. And I refute to argue any further.
  • + 1
 *refuse. And we must look like two armless dudes fighting. Big Grin
  • + 2
 Sorry, this spell check isn't particularly advanced.
  • + 1
 I was typing from my phone at work and didn't think about it.
  • + 1
 what about fox float fork ... they have an coil spring instead of a negative chamber. Interesting solution too.
  • + 1
 I want a rear shock that has the decals of a redbull can. It would give me winggssssssssssssssss!
  • + 1
 Did I read somewhere that rockshox did away with the neg. air spring on the new Reba forks?
  • + 1
 -Thanks PINKBIKE ......... Just got new Dual Air ROCKSHOX .....15mm thru........
  • + 1
 has any1 read my comment that just made coil overs even more obsolete?
  • + 1
 can you make an air can out of a redbull can?
  • + 1
 but wouldn't the red bull be awfully fizzy after a long downhill?
  • + 1
 Any info about "Hammock" effect of air shocks?
  • + 1
 Or just ride a hard tail. Big Grin
  • + 1
 Does the Vivid AIR R2C come with the negative spring system?
  • - 3
 Airshock is a onesize fits all sock for the industry which has a problem with stocking (pun intended) different springs and ratios thereoff.

I use both for Dh and limit the use for air for shortstroke parkbikes where you want to filter forcespikes so as not to damage the frame. Coilspringdamper effectively split the forces between damper and spring - protecting each other and the frame and the rider. That is why they rarely fail.

Air is fine for light-use-xc-bikes.

And I just got rid of my last airfork yesterday - a Marzocchi 66 - that was a crappy piece of equipment. Set when cold, nosettings when hot, reset when hot - oh you need to bring a pump with you on the track... Now its coilsprung Domain and Boxxer allover. There is a reason why dh is the pacesetter - junk has no acceptance with the community.
  • + 2
 Wow, you should say that to the engineers of the suspension industry, maybe they haven't thought about that!
  • + 2
 Oh yes, and tell them slopestyle riders to use coil shocks on their bikes, because obviosly air is for sissy XC bikes.
  • + 5
 Haha dude is runnin a domain and talkin' about junk being unacceptable hahahaha
  • + 1
 air is fine for slope style and xc. Slopestyle is short duration and lots of cooling time. Xc is slow and stroke is short. I have an complete airbike for slopestyle...doing dh ruins the seals in a hurry.

Domain is a perfectly capable and durable dc-fork with long service intervalls. Try to see beyond the hype. Also run Boxxer - give and take.

Again - airshocks are prefered by the industry because they are cheap to make and sell for a better price and there is no stocking cost with various coilsprings. OEM like airshocks because they only need one shock and no springs. Resellers like airshocks because they do not have to stock springs. Who fixes and services airshocks? Specialized aftermarket outlets. Are airshocks better for riding? Hell, no.
  • + 1
 Does the rockshox boxxer worldcup have a negative spring?
  • + 1
 Used to think I was intelligent until I read this !
  • + 1
 Very informative. Good Tech Toosday. (As Mike Levy pronounces it!)
  • + 2
 how do you guys say it? tchuseday? Razz
  • + 2
 Not far off actually! lol
  • + 2
 hahah Razz
  • + 1
 jaja Wink soon to be tuesday here in england
so he aint far off
  • + 1
 well done RC. thanks for the info!
  • + 1
 Still heavier than air!
  • + 1
 Amazing thansk a lot for the info
  • + 1
 Sympatic guy and good explanation tup
  • + 1
 What a good video! Very informative!
  • + 1
 i run and love my air fork. but will stick with coil rear for now.
  • + 2
 what about a Ti Spring?
  • + 1
 if you want to save weight, drink redbull?
  • + 1
 That guy is ace. Like
  • + 0
 Seems like a coil is mostly good for Reliability and that is it.
  • - 3
 Sat here... Read all that... Haven't the slightest clue what it all means :L why don't they write it so it's simple for all to understand
  • + 4
 It's probably as simple as they can make it. Shocks are pretty complex, especially these days with their negative air chambers and such. That's why I just let the guys at Fox do all the hard thinking!
  • + 2
 It's basically just saying that normally air shocks at rest have x amount of pressure acting on the inside of the chamber and piston head, and to make the piston move you have to overcome that x pressure in order to move the piston - leading to a "stickiness" because there is no head movement until x amount of pressure is exerted. In this system we can say that for simplicity sake the piston has a net pressure of 1x that must be overcome. With a negative chamber there is a sort of air pillow, so the piston head has x amount of pressure on both sides of the head, so a net pressure of 1x on both sides of the piston allowing it to sort of hover within an amount of its travel. A pressure of 1x on both sides of the piston (1x in the chamber, -1x in the negative spring) allows the shock to essentially have a net pressure of 0 since the two chambers cancel eachother out. This hovering means that while you may still have 1x pressure in the piston, you don't have to overcome any of that static pressure since the shock is balanced. So; to wrap things up, in order to move a regular air shock you need to apply at least 1x pressure, since that is the amount in the piston (force needed to engage must be = or > 1x pressure acting upon piston head) but with a negative shock, you only need to exert any pressure above 0x pressure (force needed to engage must = or be > essentially zero since [-1x + 1x = 0]).
  • + 2
 I understand the concept but I'm gonna be honest... I don't think that simplified things. haha
  • + 1
 Haha well for callum's sake: think of a shock as a balance scale, the piston head being the centre point, and the amount of pressure on either side are the weights to each end. A regular air shock is unbalanced in that, one side of the piston has more pressure in it than the other, rendering the shock unbalanced.. imagine a heavy weight on one end of a scale, the scale tilts to that side. In order to raise that weight (or move the piston) you must put an equal amount or more weight on the scale (equal or more pressure on the shock in order to move it). Now with a negative spring, there is closer to equal pressure on either side of the piston (almost equal mass on each end of the scale), so although one side of the scale is still lower than the other, you need less weight to become equal... which means! there is close to or equal to a net mass of zero on the scale, making it easier to move either side... or in the case of the shock, making it easier to engage movement of the piston. I'm not sure if that makes sense but I hope it did.
  • + 2
 sort of got it. ive a dhx5 and i dont have a problem with it. infact i think id prefer to ride with it than an air shock, even with the weight advantage thanks for explaining it tho!
Below threshold threads are hidden

Post a Comment



Copyright © 2000 - 2019. Pinkbike.com. All rights reserved.
dv56 0.142862
Mobile Version of Website