Has anyone tried nitrogen in air forks?

I use it in my MTB shocks and such... Not sure if it really makes that much of a difference to be honest.

The air you pump in is 80% nitrogen. Pure Nitrogen reacts exactly the same way to changes in pressure and temp as any other gas.

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.

ando wrote:

The air you pump in is 80% nitrogen. Pure Nitrogen reacts exactly the same way to changes in pressure and temp as any other gas.

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.

Then why do truckers use nitrogen to purposely keep their tires from changing pressure throughout changing tempatures?

m.hardesty16 wrote:

Then why do truckers use nitrogen to purposely keep their tires from changing pressure throughout changing tempatures?

Uhh, you should look up the ideal gas law...

ando wrote:

The air you pump in is 80% nitrogen. Pure Nitrogen reacts exactly the same way to changes in pressure and temp as any other gas.

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.

m.hardesty16 wrote:

Then why do truckers use nitrogen to purposely keep their tires from changing pressure throughout changing tempatures?

zehn wrote:

Uhh, you should look up the ideal gas law...

Im no science teacher but ive seen trucks pull up next to me with stickers claming to fill tires with nitrogen. Even googling it mentions that its less likely to escape through rubber.

Nitrogen acts under the same laws as any other compressable gas, and still changes with temps. From my understanding the larger molecule and lack of oxygen makes that process sliglhly slower. I have used it in my own SFF TAC forks, and still exprience pressure change. My biggest gripe with this is outside of some crazy temprature swing, the majority of the riders out there can't ride hard enought for the forks to heat up and affect their performance.

I drag race regularly. We have tested air vs nitrogen Set tires at 6.5 cold, do burn out and make run. recheck at turn off road. Air pressure is at 8.5-8.5 depending on track surface temp. Use nitrogen in same manner and start at 6.5 lbs. Recheck at turn off road and have 7.1-7.2 lbs of pressure. Now starting at 7.5 lbs cold. The tires hit better and with better reaction time compared to air starting at 6.5 lbs.

AND so why do nascar cars use the nitrogen? Have you heard a crew chief lowered his tire pressure .25 of a pound?

And the theory of losing less air is hard to swallow. We don't use tubes any more. We use Dawn to seal sidewalls of tires

PV=nRT

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

Anytime you heat a gas you will experience pressure change. Thermal transfer rates of different gases is huge, and why truckers keep a consistent blend for efficiency in their tires. Outgassing through the rubber is a old wise tale. Yes a tire can outgas but not nearly at the rate you will destroy it with use lol.


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.

Use nitrogen in the SM tyres, carry a tank in the truck. Better temp stability as the tyres get hot, which is noticable in an 18+2 race when its hot

FHKRacingZ wrote:

Anytime you heat a gas you will experience pressure change. Thermal transfer rates of different gases is huge, and why truckers keep a consistent blend for efficiency in their tires. Outgassing through the rubber is a old wise tale. Yes a tire can outgas but not nearly at the rate you will destroy it with use lol.


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.

What exactly do you mean by “thermal transfer rate”? Oxygen and nitrogen have identical heat capacities. And they both conform to Boyle’s Law.

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?

I suspect that the differences people are seeing in using air vs nitrogen are due to the moisture content.

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.

ando wrote:

I suspect that the differences people are seeing in using air vs nitrogen are due to the moisture content.

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.

Nitrogen won't carry moisture in any case...at least not at a percentage that makes a measurable difference

If you could empty it into balloons at the end of the day, I'm in.

NJKawi913 wrote:

Nitrogen acts under the same laws as any other compressable gas, and still changes with temps. From my understanding the larger molecule and lack of oxygen makes that process sliglhly slower. I have used it in my own SFF TAC forks, and still exprience pressure change. My biggest gripe with this is outside of some crazy temprature swing, the majority of the riders out there can't ride hard enought for the forks to heat up and affect their performance.

I notice a pressure change every time i ride, and i wouldn't consider myself a very fast rider by any means. I'm a 30yr old guy that can hang with 16 year olds in the C class, and hang with B class Vet riders.

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.

Nitrogen is not a true inert or noble gas but it still works well as an inert gas because it doesnt react with anything else for the most part . We use it as an inert gas to prevent oxidation in welding refrigeration pipe. Any true inert gas would be too expensive.
I think one advantage would be preventing condensation inside suspension components.

Sincerely,
Not an engineer,

ando wrote:

What exactly do you mean by “thermal transfer rate”? Oxygen and nitrogen have identical heat capacities. And they both conform to Boyle’s Law.

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?

Very well aware of nitrogens bond and the parameters it takes to react. None of which would ever be met in a fork tube, which in most applications nitrogen is used, is inert "enough"...

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.

SCR wrote:

Nitrogen is not a true inert or noble gas but it still works well as an inert gas because it doesnt react with anything else for the most part . We use it as an inert gas to prevent oxidation in welding refrigeration pipe. Any true inert gas would be too expensive.
I think one advantage would be preventing condensation inside suspension components.

Sincerely,
Not an engineer,

You are 100% right! My company builds hydrocarbon gas and alcohol extraction equipment. We burn through bottles of argon back-purging all the time.

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

This is exactly why I posed the question, it's got some people thinking. I'm an engineer as well, though electrical.
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.

Whoever said moisture wins. Although there are some differences, they are very minuscule when comparing to the effects of a little water in your air. Vaporizing liquid makes a huge difference.

Sincerely, all chemical engineers.

Does any of this discussion make a real world difference?

Sincerely,

Not an engineer

The only thing that made a real difference with my air forks was putting the glide kit in. Air forks by their nature have more resistance. Eliminate as much of the resistance as possible and they start feeling like normal forks.

I would think regular air increases pressure as the fork increases in heat.

ando wrote:

The air you pump in is 80% nitrogen. Pure Nitrogen reacts exactly the same way to changes in pressure and temp as any other gas.

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.

m.hardesty16 wrote:

Then why do truckers use nitrogen to purposely keep their tires from changing pressure throughout changing tempatures?

Cause they got suckered into the marketing gimmick and paid an extra $100 to have a sticker put on the tire.

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.

The nitrogen works.... I'm no science nerd, but I do have a friend that had a business building nitrogen compressors and tested with trucking companies. It does work in tires.....

i have a pic somewhere from mxgp lommel where you see filling up the HRC honda showa forks with nitrogen . so i suppose it will have it benefits.

Street car, would never waste the money. Race tures and shocks, yup. H2O,H2O,H2O.
It is noticeable. You couls use oxygen or acetylene and see the same result.

Why aren't more of you riding with air in your shock instead of nitrogen LOL!


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....