Nitrogen instead of nomral air in rear shock??- Mtbr.com
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  1. #1
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    Nitrogen instead of nomral air in rear shock??

    Would it be beneficial to fill a DHX 5 with nitrogen (or another gas) instead of just regular surrounding air?

    If so, what would be the benefits and how could I go about doing so?


  2. #2
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    Nitrogen has thicker molecues then air so it stays in the chamber longer (less chance of it slowly leaking out)

    that is the only benefit.....IMO I would just stick to air unless the nitrogen is easily attainable
    Last edited by SHIVER ME TIMBERS; 12-30-2009 at 11:55 AM.
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  3. #3
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    Ignore the assclown.

    Nitrogen CAN seep out less if a system already has a problem with normal air leaking out. Bike stuff gets the pressure checked often enough for it to be a non-issue.

    The more noble reason is to keep the shock running cooler. Nitrogen can transfer heat out of the shock oil much more effectively than normal air can.
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  4. #4
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    Nitrogen is also less affected by temperature changes if I recall, although a shock will probably warm up pretty quickly during usage anyway.
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    nitrogen = less prone to heating up, that's why race teams use them for air in their tyres, to maintain the optimum PSI on their tires.
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    One of my friends had his rear shock rebuilt by his moto mechanic with nitrogen and im pretty sure thats what screwed his shock up
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    I think the moto guys use nitrogen for heat reasons, and it apparently makes a huge difference in their shocks...

    but would it really make a difference in a DH shock? anyone have experience?

  8. #8
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    Air is 78% nitrogen , you would reap very little benefit from using 100% nitrogen .

  9. #9
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    The reason nitrogen gets used in shocks is because of the lack of moisture.
    Dried air could be used for the same reason.

    If a shock filled w/ 'normal' is cycled fast and often enough, it will begin to heat up. Moisture will expand and change the dynamic of the shock (basically increase spring rate).
    MTBs typically do not go fast enough to heat up the shocks significantly and warrant nitrogen (or other arid gasses)
    Honestly... ahh I give up

  10. #10
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    Quote Originally Posted by Metanoia
    nitrogen = less prone to heating up, that's why race teams use them for air in their tyres, to maintain the optimum PSI on their tires.
    no less chance of seeping out
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  11. #11
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    Only took 10 posts to get the right answer.....

  12. #12
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    Quote Originally Posted by highdelll
    The reason nitrogen gets used in shocks is because of the lack of moisture.
    Dried air could be used for the same reason.

    If a shock filled w/ 'normal' is cycled fast and often enough, it will begin to heat up. Moisture will expand and change the dynamic of the shock (basically increase spring rate).
    MTBs typically do not go fast enough to heat up the shocks significantly and warrant nitrogen (or other arid gasses)
    Ah yes very good answer. This is one of the main reasons we use it on aircraft. Moisture can also form corrosion on the internal components and start to wear things such as seals much quicker. It is also effected less by altitude changes. The only thing I will disagree with is that a MTB shock runs hotter than most because they hold a smaller volume of oil and have more duty cycles due to their short stroke compared to a moto or something like that.
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    2nd that. Hit a run that is 10 minutes long or more, and rough as hell - constant suspension activity. Then reach down and touch the reservoir of your shock.
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    Quote Originally Posted by Metanoia
    nitrogen = less prone to heating up, that's why race teams use them for air in their tyres, to maintain the optimum PSI on their tires.
    bingo.

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    Try a 4 minute run at Northstar!
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    A 4 minute run at Northstar is nothing.
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    SMT, you need to take a chemistry class. Nitrogen gas is (obviously) ~100% Nitrogen. Normal air, that would surround a tire for instance, is ~78% Nitrogen. Gas will diffuse from high concentration to low concentration, meaning the Nitrogen in the tube will diffuse out of the tire. Also, because nitrogen is fairly low in molecular weight, it will diffuse fairly quickly.

    As someone correctly noted, Nitrogen gas is used because it is anhydrous.

  18. #18
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    Quote Originally Posted by Diggidy
    SMT, you need to take a chemistry class. Nitrogen gas is (obviously) ~100% Nitrogen. Normal air, that would surround a tire for instance, is ~78% Nitrogen. Gas will diffuse from high concentration to low concentration, meaning the Nitrogen in the tube will diffuse out of the tire. Also, because nitrogen is fairly low in molecular weight, it will diffuse fairly quickly.

    As someone correctly noted, Nitrogen gas is used because it is anhydrous.
    contrary...the reason they use nitrogen in car tires is it seeps out slower because they are thicker molecues....therefore tire stay at same pressure longer then just air...
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    Quote Originally Posted by SHIVER ME TIMBERS
    contrary...the reason they use nitrogen in car tires is it seeps out slower because they are thicker molecues....therefore tire stay at same pressure longer then just air...
    I'm sure that's an advantage SMT but it's not the primary reason people use nitrogen in their tires. Highdelll hit the nail on the head. Really, the only reason nitrogen is even used over other gases is because it's the easiest to isolate. CO2 is cheaper but it has other downfalls.
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  20. #20
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    Isn't there already nitrogen in some rear shocks?

    Seems to me that my fox van r has nitrogen in it.
    Just curious
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  21. #21
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    Quote Originally Posted by ridefreeride
    Isn't there already nitrogen in some rear shocks?

    Seems to me that my fox van r has nitrogen in it.
    Just curious

    yes fox does a lot of their coils with nitrogen
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  22. #22
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    Quote Originally Posted by Bikesair
    I'm sure that's an advantage SMT but it's not the primary reason people use nitrogen in their tires. Highdelll hit the nail on the head. Really, the only reason nitrogen is even used over other gases is because it's the easiest to isolate. CO2 is cheaper but it has other downfalls.
    for everyday passenger cars that is the primary reason....for people who don't check air pressure in tires as much....just less maintenance
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  23. #23
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    the only difference is that nitrogen is clean and dry. compressed atmospheric air, even in the driest places, has water in it. especially in a air shock that gets heated up, water is going to make an impact on performance.

    if you had a compressor setup with driers, pure nitrogen would be useless. since most people dont, nitrogen fills sort of make sense.

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    Quote Originally Posted by SHIVER ME TIMBERS
    contrary...the reason they use nitrogen in car tires is it seeps out slower because they are thicker molecues....therefore tire stay at same pressure longer then just air...
    I don't know what you mean by "thicker", but the three main components of air are Oxygen, Nitrogen, and Carbon Dioxide. N2 is the smallest of the three diatoms, as well as the least dense at 0* C.

    You can't really argue against physical properties. If you concentrate a gas inside something higher than in naturally occurs in our atmosphere, the gas will follow its concentration gradient until it reaches an equilibrium. This is why a balloon filled with helium that floats, after a few days no longer floats. The balloon leeches helium into the air surrounding it. Also, because of the root mean square velocity equation, nitrogen having a small molecular mass, will have a very fast velocity, meaning it will diffuse faster than the other gas molecules that naturally occur in air.

  25. #25
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    Has anyone filled their shock with nitrogen? How much would it cost and where can I get some?

    ...if it's cheap, I may as well give it a shot

  26. #26
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    Race cars use nitrogen in their tires to prevent moisture from entering the tire, race car tires temps easily exceed the boiling point of water at which point that moisture turns to steam causing tire pressures to increase dangerously. Tire temps commonly hover around 200F-250F once hot on the race track.

    Dried air will achieve the same function but nitrogen is commercially bottled in high pressure cylinders making them easy to procure and a small bottle can fill a lot of tires making them convenient to use and store. The other stated reasons to use nitrogen are miniscule in practice and rarely assist a tire in retaining its pressure or aid in its cooling although it is measurable (if only slightly) so not entirely untrue.

    NASCAR Information

    Fundamentally; air, oxygen and nitrogen will all behave exactly the same in terms of pressure change for each 10 degrees of temperature change. However temperature alone is not the whole story.

    Ambient air contains moisture, nitrogen does not. If moisture is present it contributes to a greater change in pressure simply because at lower temperatures water condenses to become a liquid. The liquid form of water occupies very little volume and contributes only a negligible pressure to the tire. But at higher temperatures, such as those in a running tire, water evaporates inside the tire and becomes a gas which increases pressure in the tire.

    Ambient air contains about 21% oxygen. Oxygenís smaller molecular size allows it to permeate through the rubber of the tire. By inflating with nitrogen, which is much less permeable than oxygen, the pressure changes due to oxygen loss are greatly reduced.

    The racing industry is correct; nitrogen is more predictable. Because nitrogen is dry it has no moisture to contribute extra pressure changes with temperature. Because nitrogen permeates out much slower than oxygen pressure changes due to that leakage are almost eliminated compared with ambient air.
    http://www.getnitrogen.org/sub.php?view=nascar
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  27. #27
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    Quote Originally Posted by Diggidy
    I don't know what you mean by "thicker", but the three main components of air are Oxygen, Nitrogen, and Carbon Dioxide. N2 is the smallest of the three diatoms, as well as the least dense at 0* C.
    .
    Um where did you read that N2 is the smallest. I know that nitrogen is a bigger atom than oxygen so I would be inclined to believe that the diatom of each would fallow the same principle...
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  28. #28
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    Soooooo much ignorance. I don't think we need more answers as several bright dudes in the forum have answered correctly, but just to make sure:

    Pressurized nitrogen is used because it's almost inert and lacks moisture, two properties you definitely want in an application in which you need constant/predictable pressure and corrosion resistance; shocks.

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    Quote Originally Posted by Bikesair
    Um where did you read that N2 is the smallest. I know that nitrogen is a bigger atom than oxygen so I would be inclined to believe that the diatom of each would fallow the same principle...
    Yeah, I don't know why I said that. Got my periodic trends reversed. Still, as far as atomic radii is concerned, nitrogen is a very small molecule, and smaller than the carbon atoms that compose the majority of rubber's chemical makeup.

  30. #30
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    nitrogen sounds cooler.....
    I'm GNARcissistic

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    Lol, I love it when people talk about stuff on the internet which they obviously have no practical experience with.

  32. #32
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    Quote Originally Posted by 4JawChuck
    Race cars use nitrogen in their tires to prevent moisture from entering the tire, race car tires temps easily exceed the boiling point of water at which point that moisture turns to steam causing tire pressures to increase dangerously. Tire temps commonly hover around 200F-250F once hot on the race track.

    Dried air will achieve the same function but nitrogen is commercially bottled in high pressure cylinders making them easy to procure and a small bottle can fill a lot of tires making them convenient to use and store. The other stated reasons to use nitrogen are miniscule in practice and rarely assist a tire in retaining its pressure or aid in its cooling although it is measurable (if only slightly) so not entirely untrue.

    NASCAR Information

    Fundamentally; air, oxygen and nitrogen will all behave exactly the same in terms of pressure change for each 10 degrees of temperature change. However temperature alone is not the whole story.

    Ambient air contains moisture, nitrogen does not. If moisture is present it contributes to a greater change in pressure simply because at lower temperatures water condenses to become a liquid. The liquid form of water occupies very little volume and contributes only a negligible pressure to the tire. But at higher temperatures, such as those in a running tire, water evaporates inside the tire and becomes a gas which increases pressure in the tire.

    Ambient air contains about 21% oxygen. Oxygen’s smaller molecular size allows it to permeate through the rubber of the tire. By inflating with nitrogen, which is much less permeable than oxygen, the pressure changes due to oxygen loss are greatly reduced.

    The racing industry is correct; nitrogen is more predictable. Because nitrogen is dry it has no moisture to contribute extra pressure changes with temperature. Because nitrogen permeates out much slower than oxygen pressure changes due to that leakage are almost eliminated compared with ambient air.



    http://www.getnitrogen.org/sub.php?view=nascar
    there it is right there....Nitrogen molecules are bigger
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  33. #33
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    Quote Originally Posted by Diggidy
    I don't know what you mean by "thicker", but the three main components of air are Oxygen, Nitrogen, and Carbon Dioxide. N2 is the smallest of the three diatoms, as well as the least dense at 0* C.

    You can't really argue against physical properties. If you concentrate a gas inside something higher than in naturally occurs in our atmosphere, the gas will follow its concentration gradient until it reaches an equilibrium. This is why a balloon filled with helium that floats, after a few days no longer floats. The balloon leeches helium into the air surrounding it. Also, because of the root mean square velocity equation, nitrogen having a small molecular mass, will have a very fast velocity, meaning it will diffuse faster than the other gas molecules that naturally occur in air.
    wrong.....Nitrogen is a bigger molecule then oxygen
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  34. #34
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    I knew I would not be disappointed with this thread when I saw "Nitrogen" in the title, and 35 posts already...



    The real question is how many people would actually notice a difference in bike/suspension behavior during their runs due to use of air instead of pure nitrogen in their shocks ?

  35. #35
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    Quote Originally Posted by Iceman2058
    The real question is how many people would actually notice a difference in bike/suspension behavior during their runs due to use of air instead of pure nitrogen in their shocks ?
    Probably no one, if you didn't tell them.

    I've read that many suspension tuners in the moto world will use air when making many changes on a shock during a day or testing weekend. They just fill ~5 psi less than they would with nitrogen to compensate for the expansion from moisture. Once everything is sorted out and final valving is picked most will fill with nitrogen.

    How hot do MTB shocks get? I've gotten my motorcycle shock hot enough that you can't touch it plenty of times. I've read that 200+ degrees is common, and one tuner mentioned a pro topping 275F on a hot summer day in the whoops. Just the unsprung weight in the rear of a motorcycle is probably equal to or greater than the weight of some complete bicycles. Takes a lot of damping to deal with those forces.
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    Quote Originally Posted by SHIVER ME TIMBERS
    wrong.....Nitrogen is a bigger molecule then oxygen
    First, we already got that out of the way a few posts up. Phenomenal reading comprehension.

    I still don't quite get what you think that proves though? Other people, including myself, have said the real reason N2 is used is because it's anhydrous, and so it has more consistent thermal expansion.

    You seem to have a pretty tenuous grasp on what we're talking about, so I'm just going to stop.

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    Here's a technical explination of oxygen vs nitrogen in respects to rubber permeation.

    http://www.getnitrogen.org/pdf/graham.pdf
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    Quote Originally Posted by adam728
    Probably no one, if you didn't tell them.

    I've read that many suspension tuners in the moto world will use air when making many changes on a shock during a day or testing weekend. They just fill ~5 psi less than they would with nitrogen to compensate for the expansion from moisture. Once everything is sorted out and final valving is picked most will fill with nitrogen.

    How hot do MTB shocks get? I've gotten my motorcycle shock hot enough that you can't touch it plenty of times. I've read that 200+ degrees is common, and one tuner mentioned a pro topping 275F on a hot summer day in the whoops. Just the unsprung weight in the rear of a motorcycle is probably equal to or greater than the weight of some complete bicycles. Takes a lot of damping to deal with those forces.
    Nitrogen is cheap. I worked as a mechanic at a yamaha shop for years, I would just take are whole bottle to the track.

    Fox builds air shocks for quads and pitbikes. I noticed on long motos some change in low speed compression and rebound but it wasn't that bad. I had a float on my KLX110 and tried using nitrogen a few times instead of air. It wasn't enough of a differnece for me to bother doing.


    I am supprised that people are not more concerened about running a lighter weight oil then running nitrogen. Modern MX suspension uses 0 Wt so the viscosity does not change with heat. It would be a much more notcieble difference in getting consistent dampening to set up this way.

  40. #40
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    Quote Originally Posted by 181picklz
    Nitrogen is cheap. I worked as a mechanic at a yamaha shop for years, I would just take are whole bottle to the track.

    Fox builds air shocks for quads and pitbikes. I noticed on long motos some change in low speed compression and rebound but it wasn't that bad. I had a float on my KLX110 and tried using nitrogen a few times instead of air. It wasn't enough of a differnece for me to bother doing.


    I am supprised that people are not more concerened about running a lighter weight oil then running nitrogen. Modern MX suspension uses 0 Wt so the viscosity does not change with heat. It would be a much more notcieble difference in getting consistent dampening to set up this way.
    Nitrogen may be cheap, but zero-loss chucks and the regulators cost a bit more than your average DIY guy will probably want to spend.

    Oil weight has little to do with viscosity change due to temperature. Viscosity Index shows how a oil reacts as temp changes. A 15W oil may be more stable than a 0W, or vice versa.
    A great link for suspension fluids, put together by PVD, a regular here.
    https://www.pvdwiki.com/index.php?ti...spension_Fluid

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    I have NITROGEN in my Avalanche FORK and rear shock on my Canfield I love the way craig at AVY sets it up nothing but the best suspension out even better then ELKA. I know i am going to here about that comment but if you have ridden AVY you will know what I am talking about. just my .02 stiff and bottomless suspension ....THANKS CRAIG AVY RULES ...

  42. #42
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    Yes, and I love my new Avalanche shocks, but what the hell does that have to do with this thread? (yes, theyare better than Elka because there are more tuning parameters and even more fluid flow, but that's also why they costs so much).

    Also, pretty sure that there is no nitrogen charged reservior in the Avalanche fork. The avalanche fork is an open-bath fork, as such it doesn't use a nitrogen charged reservior. This was feature on some White Brothers and BOS forks that use closed-cartridge dampers, not very common due to minimal cavitation that forks encounter.
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  43. #43
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    Ok, thread wrap up thus far.

    Nitrogen sounds cooler, has larger molecules than oxygen, nitrogen is not effected by heat, builds no moisture, both push and cr1 use it when they tune shocks, SMT has little to no idea of the actual benefits of it


    Did i miss anything?

  44. #44
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    Quote Originally Posted by Dynamatt
    Ok, thread wrap up thus far.

    Nitrogen sounds cooler, has larger molecules than oxygen, nitrogen is not effected by heat, builds no moisture, both push and cr1 use it when they tune shocks, SMT has little to no idea of the actual benefits of it


    Did i miss anything?

    The part about where you can buy some nitrogen?

  45. #45
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    Quote Originally Posted by Diggidy
    You seem to have a pretty tenuous grasp on what we're talking about, so I'm just going to stop.

    Have you not read anything else posted by SMT? Nothing new....

  46. #46
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    Quote Originally Posted by [email protected]
    The part about where you can buy some nitrogen?
    Your local welding shop should carry Nitrogen in MANY different size tanks. But i found this that you could probably retrofit to use via schrader valve and a regulator to set propper pressure


    http://www.wineenthusiast.com/nitrot....asp?AfID=ZNXT

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    Oh this thread is brilliant, please don't stop people.

    Trained scientist here, so could advise the reason all of this works, but it is more fun to watch.

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    Could you put helium in tires to save weight?
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  49. #49
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    Quote Originally Posted by huntandride
    Could you put helium in tires to save weight?
    Holy S##T, Watch out for that brick wall!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! AAAAAAHHHAHAHAHAHAHAH!!

    If you watch mythbusters you'll get the answer to that question
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  50. #50
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    Quote Originally Posted by Diggidy
    First, we already got that out of the way a few posts up. Phenomenal reading comprehension.

    I still don't quite get what you think that proves though? Other people, including myself, have said the real reason N2 is used is because it's anhydrous, and so it has more consistent thermal expansion.

    You seem to have a pretty tenuous grasp on what we're talking about, so I'm just going to stop.
    I just read what you wrote...not reading down to everyone else....

    and you are right the main focus is lack of moisture and slower temp difference
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  51. #51
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    Jeez, a brand new thread on this subject.....

  52. #52
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    Quote Originally Posted by Demodude
    Holy S##T, Watch out for that brick wall!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! AAAAAAHHHAHAHAHAHAHAH!!

    If you watch mythbusters you'll get the answer to that question
    what happen
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    Appologies for bringing this back from the dead, but, who would know how much cooler a Fox X2, RP23, or CTD would run with nitrogen V's air when at race conditions in the summer heat ? I know its a daft questions but I would realy appreiciate an answer from someone who actually knows or has a rough idea, no guessing, thats my job.
    Thanks in advance.

  54. #54
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    Quote Originally Posted by karpiel View Post
    Appologies for bringing this back from the dead, but, who would know how much cooler a Fox X2, RP23, or CTD would run with nitrogen V's air when at race conditions in the summer heat ? I know its a daft questions but I would realy appreiciate an answer from someone who actually knows or has a rough idea, no guessing, thats my job.
    Thanks in advance.
    The heat shedding abilities of the shock are unchanged going to N2.
    N2 is just moisture free whereas atmosphere air has varying amounts of moisture (humidity).
    All air expands when heated, this is unavoidable. But N2 with no moisture will always expand at a known/ consistent rate whereas air with varying amounts of moisture in it expands at an unknown/ inconsistent rate as a result of the moisture content being dependent on other factors (i.e. time of day, location, weather).
    Hope that helps.

    Sent from my SM-G892A using Tapatalk

  55. #55
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    Thank you very much, I knew someone would help, 👍🏼

  56. #56
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    Gas laws don't take into consideration what the gas actually is. The gas law just works.

    p1/t1 = p2/t2. So as temp rises, so does pressure. Mixed gas, pure nitrogen, doesnt matter. Temp goes up, gas pressure goes up. They all go up the same.

    But air in a shock or fork doesnt overheat. The damper oil does. The best way to fight this is with a high quality high VI oil.

  57. #57
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    Quote Originally Posted by One Pivot View Post
    Gas laws don't take into consideration what the gas actually is. The gas law just works.
    Not true at all. Taking short cuts is a real trend in society, and 'science' has become so perverted in the last 50 years. It no longer is based on facts. But rather opinion and theories. It's a sad truth.

    Taken straight from Wikipedia.
    Ideal Gas Law.
    "The ideal gas law, also called the general gas equation, is the equation of state of a hypothetical ideal gas. It is a good approximation of the behavior of many gases under many conditions, although it has several limitations."

    Avogadro's law.
    "The law is named after Amedeo Avogadro who, in 1812,[2][3] hypothesized that two given samples of an ideal gas, of the same volume and at the same temperature and pressure, contain the same number of molecules. As an example, equal volumes of molecular hydrogen and nitrogen contain the same number of molecules when they are at the same temperature and pressure, and observe ideal gas behavior. In practice, real gases show small deviations from the ideal behavior and the law holds only approximately, but is still a useful approximation for scientists."

    N2 is cheap, readily available and has a number of advantages over 'air' for both tires and dampers.
    Please don't spread incorrect theories and information that we know is wrong. Just because it is 'close enough'

    If your whole argument is that air is good enough then say the truth. 'nitrogen is better, but air is close enough (because you're a hack)'.
    Sort of how to some people using white sugar instead of brown sugar might be good enough, and not noticeable or measurable to most people......

  58. #58
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    Please explain Grand Wizard.

    Elaborate, go into detail.

    Demonstrate that you know what you are talking about.
    Why would I care about 150g of bike weight, I just ate 400g of cookies while reading this?

  59. #59
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    ... are you seriously trying to discredit ideal gas laws? Thats not internet hack science, its an established gas law.

    I assure you, the basic principals of science are plenty sufficient for bicycle use.

  60. #60
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    Quote Originally Posted by One Pivot View Post
    ... are you seriously trying to discredit ideal gas laws? Thats not internet hack science, its an established gas law.
    Only trying to discredit misinformation.

    A statement such as "Gas laws don't take into consideration what the gas actually is. The gas law just works." is very misleading and deceptive, without proper context. Because going by the ideal gas law you are technically correct. They don't take into consideration what the gas actually is. But the ideal gas law itself is wrong. Since actual laws of gas do take into consideration what the gas actually is.

    As I said in my last post. This is common in engineering to take short cuts. It's the same culture that brings us cheap shit in every day life. Taking short cuts to cut time/cost.
    Your comment about the ideal gas law being 'plenty sufficient for bicycle use' is a prime example of this. It's good enough.......
    But unfortunately good enough or sufficient doesn't make it right.

    This is a discussion about whether using nitrogen instead of air is better. The answer is a clear yes. That is known just by looking at some simple facts about the different gases, and also by the fact that we are talking about a bottle of quality controlled gas compared with an unknown air quality.
    If you want to question whether people will notice it, or if one is better over the long term then you are welcome to discuss that.
    All I know is that one is better than the other. How much difference is really hard to measure and I will leave someone else to argue that.

  61. #61
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    One other advantage of N2 that can have some value is that the total lack of moisture can prevent corrosion caused by the water in normal air on delicate parts.

    Sent from my SM-G892A using Tapatalk

  62. #62
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    This is like putting nitrogen in car tires.

    What do you do when you have to refill them?

    I, cynically, believe that most if the benefit goes to the shop.

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