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Just curious if anyone has tested running nitrogen in their air forks? You'd think maybe some factory teams toyed with it. I personally have never ridden on a set of air forks, but have read a lot about the inconsistency and how they change throughout the day. Seeing as how they rely on air pressure and you're pumping air into them, it makes sense that they change throughout the day. The air you're pumping in changes density with temperature and humidity. Nitrogen is an inert gas and doesn't react to temperature changes near as much as air.
I'd bet it would make a ton of difference in the consistency issues I've read about.
I'd bet it would make a ton of difference in the consistency issues I've read about.
Being in a sealed container the humidity can’t change. In any case the relative humidity of the air will be at its worst when the air is cold i.e. when you put it in, so heating during use won’t make any moisture condense.
If you are worried about the moisture in the first place you can dry the air before it goes into the fork with much less effort and expense than using nitrogen.
The Shop
AND so why do nascar cars use the nitrogen? Have you heard a crew chief lowered his tire pressure .25 of a pound?
The only difference between the two would be n
n is the number of moles
The n factor would be smaller for pure nitrogen (pretty sure about that) so the Pressure*Volume would change less with increase in T
The guy claiming nitrogen makes no difference than regular atmosphere must of missed a basic chemistry class. Atmospheric air, even if ran through a filter dryer, is totally inconsistent. Being inconsistent means different blend of gases that expand at different rates...Which means finding consistency can be hard.
On warmer days, you will heat soak the metal and transfer external heat into your air chamber (More than what is already generated by the mechanics of the fork). That is why using a 100% tested, inert gas is huge..Eliminates one variable from why your fork may/may not be working how you want.
Sincerely,
An Engineer.
And air is pretty much the same blend everywhere, last time I checked, so I’m not sure what you mean by inconsistent.
Do you have data to share that can explain?
Sincerely
Another engineer
PS you do know that nitrogen is not actually an inert gas?
If you use air, it comes from whatever compressor is handy, with or without a drying system. The most common source of nitrogen however is commercially produced and sold to a specification which includes (practically) zero moisture. Moisture will make a difference to the behaviour of the gas as it heats up.
There is nothing about the physical properties of oxygen and nitrogen that would account for them behaving differently in a tyre or forks.
The air pressures in all 3 of the chambers on my '15 SFF TAC forks increase by the end of a moto. My forks seem to soften up a tiny bit as they heat up. This is probably because the balance chamber volume is less than the inner chamber volume and the pressure increases more in the balance chamber than the inner chamber. My shock reservoir gets piping hot, to the point where it stings my right leg sometimes. That having been said, i still think my suspension works very well.
I think one advantage would be preventing condensation inside suspension components.
Sincerely,
Not an engineer,
Although air in the atmosphere may be very similar the moisture content sure is not.. Compressed air always contains water in both the liquid and gas phase. Anytime you increase the temperature of compressed air, you also increase its vapor holding capacity.
Oxygen and nitrogen do not have identical heat capacities. Although close, its around a 12% different if I remember correctly. What is important is water vapor carries a 50% heat capacity difference.
We didn't even mention aerosols in the air as well..
Is there going to be a noticeable difference in using nitrogen vs compressed air? Probably not, but as you know, if you dive into the numbers and had enough data, you could pin-point the difference.
Pit Row
Condensation is something that happens a lot as anybody who has seen dirty shock oil understands. Only way to fix that would be vacuum jacketed fork tubes. I don't see that happening anytime soon lol
I'd suspect the volume of air used in forks isn't enough to see a real improvement if filled with nitrogen. While the properties are different from air, it's not very much. I would suspect that there would be a measurable difference in pressure, though minimal. I think the biggest gain would come from the lack of moisture.
I'd be very interested to see a true test done with a pro level rider that would really get the components heat saturated over a 20-30 minute moto.
Sincerely, all chemical engineers.
Sincerely,
Not an engineer
For a daily driver there's really not going to be much difference. For a high performance application, like the drag racer or supermoto guy, there could be a slight increase in stability between cold and hot pressure. Less change would make it easier to hit your ideal hot pressure.
Unless you really need that extra 1% you're throwing your money away. As far as tires go anyway. I'd think the effect might be more noticeable in suspension.
It is noticeable. You couls use oxygen or acetylene and see the same result.
I have my own suspension shop now, we talked about it trying nitrogen in air forks, but after discussing it with my guru, "pun intended" and hearing his past experience with it, we realized it was not enough of a difference to bother.
I understand why HRC or other factory teams would use it. On that level at the end of a 30 min moto it may make a slight but enough of a difference to use it... 99.9% of riders would never know a difference....
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