Nitrogen versus Air - 5th gear

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I have the green caps on my tires that I fill with air. I want people to think I gullible and then: BLAMO

Air from a compressor seems to absorb a lot of moisture when the temperature increases. Filling one hundred tires in a tire shop daily, perhaps. Their plumbing system might help cool it down a bit. The only time I have seen considerable moisture at home is while sand blasting. Moisture while just topping off is probably minimal.
 
More fuel for the fire:

What is the boiling temperature of water at 30 psig (45 psia)? about 275 degrees F

What is the normal temperature buildup in a tire? about 45 degrees F

Does water vapor act like an ideal gas (like nitrogen and oxygen do) at typical tire temps and pressures? Yes, except near the dew point (the saturation point)

If the air inside an air compressor is saturated with water vapor, does the tire get filled with water saturated air? No, the pressure in a tire is much less than the pressure inside an air compressor, so what was once saturated air, no longer is.
 
It's pretty basic, water is formed in compressors depending on the water content of the air. If you want water in your tires use undried air directly from a compressed air tank. If want dry, use nitrogen. Oxygen does not bleed back onto nitrogen filled tires from the atmosphere,it can't go that direction, and it is true nitrogen escapes less through the rubber than oxygen. The bead seam is not the rubber.
 
Originally Posted By: goodtimes
Oxygen does not bleed back onto nitrogen filled tires from the atmosphere,it can't go that direction,


I believe this is untrue. I'd like it to be true, but I think it isnt.

Gases move pretty independantly of one another and I THINK the diffusion of the O2 into the tyre isn't greatly affected by the pressure differential.
 
If there's 30 psi of nitrogen inside a tyre, and it's 100% pure, then there's about 3psi of oxygen pressure on the outside of the tyre, pushing oxygen inwards.

It works both ways. If oxygen can leak out due to the 6(ish) psi of O2 partial pressure between the insides and the outside when filled with air, it WILL leak in if the tyre us pure N2.

So what if there's some water vapour...the fact that you have to drain it out of the receiver means at least that much free liquid didn't make it into the tyre, and the expansion from 100psi to 30psi nearly ensures that there's no free water in the tyre.

Does seating lubricant contain water ?
 
A tyre that's filled with air at 30psi gauge is 44.7psi absolute. For the purposes of molecular diffusion filled with 9.3psi of oxygen 34.9 psi of nitrogen, and the balance of other gasses.

The atmosphere on the outside (14.7psi) is made up of 3.1psi of oxygen, 11.5psi of nitrogen and the balance other gasses.

The molecules move through the rubber according to their respective partial pressures.

So there's 6.2psi of differential driving the oxygen through the rubber.

If you make the partial pressure of oxygen inside the tyre 0, by having pure nitrogen in there, the 3.1psi of oxygen pressure from outside the tyre is pushing oxygen into it.

about 20 years ago, a transformer expert visited one of the sites and pointed out which Tx's were likely to suffer paper degradation...the ones with the oil leaks, as that was a path for oxygen and moisture INTO the Tx.
 
Re the water being a big deal, again, partial pressures.

We'll use the 1% measure, as it's pretty close to the total amount of water vapour that air inside a tyre can hold.

Here's the table linked to in the Jalopnik article
https://jalopnik.com/heres-the-deal-with-nitrogen-filled-tires-1795659391
http://intro.chem.okstate.edu/1515sp01/database/vpwater.html

Well pick zero C, and 50C as the bookends...4.6 and 92.5mmHg respectively...0.09psi and 1.8psi respectively.

Their contribution to the 44.7psi in the tyre is 0.0009psi, and 0.018 psi respectively.

So the pressure gain that you can link to water vapour in the tyre at 1% is 0.018psi...versus about 10psi just due to the air.
 
OK, looks like damp CO2 fill is a potential go.

Need to score an old fire extinguisher and see if it can be opened, or I suppose a big pop bottle, reinforced if necessary, would do, and might be less dangerous.
 
Originally Posted By: Ducked
Originally Posted By: SteveSRT8
Glad to see all the hype debunked in a thorough and complete comparison!


IF that's sarcasm, fair enough.

If you're serious, you must have seen a different video.

Most of these auto-journo "tests" on this type of topic are almost completely worthless, and the 5th Gear ones I can remember all met or exceeded that standard.


Good catch. Got me.

While they tried to be thorough they still implied a benefit, which I never saw in any of the info I read in a search several years ago when my tire dealer wanted to install new tires with N2.

Always felt it was snake oil for sale...
 
I've been putting nitrogen in thousands of tires for over 13 years for free. Sure compressed air will work, but other than availability, how is it better? It's not, and all kinds of things are nitrogen charged, like shocks, lift struts, fire extinguishers, etc. Yes the O2, and moisture will eventually equalize in a tire, but it takes a long time, so it helps to start with as little as possible. It really helps with bead seat corrosion especially in the winter, and it leaks down slower too. I have a refrigerated air dryer on my air compressor, but I never fill tires with just that. Dry nitrogen always, with a dew point of like -60 degrees, for free. Every time you top off your tires, you replenish the O2, and water. Oxygen, and moisture are of no benefit for tires, or wheels period.
 
Last edited:
Originally Posted By: Traction
I've been putting nitrogen in thousands of tires for over 13 years for free. Sure compressed air will work, but other than availability, how is it better? It's not, and all kinds of things are nitrogen charged, like shocks, lift struts, fire extinguishers, etc. Yes the O2, and moisture will eventually equalize in a tire, but it takes a long time, so it helps to start with none. It really helps with bead seat corrosion especially in the winter, and it leaks down slower too. I have a refrigerated air dryer on my air compressor, but I never fill tires with just that. Dry nitrogen always, with a dew point of like -60 degrees, for free. Oxygen, and moisture are of no benefit for tires, or wheels period.


From cylinders of compressed nitrogen ?

How do you start from "zero" with a mounted tire, how many purges and fills do you do ?

Do you provide the customers with "tire balloons" that keep their rotating assemblies free from contact with oxygen and moisture ?
 
Originally Posted By: Shannow
Originally Posted By: Traction
I've been putting nitrogen in thousands of tires for over 13 years for free. Sure compressed air will work, but other than availability, how is it better? It's not, and all kinds of things are nitrogen charged, like shocks, lift struts, fire extinguishers, etc. Yes the O2, and moisture will eventually equalize in a tire, but it takes a long time, so it helps to start with none. It really helps with bead seat corrosion especially in the winter, and it leaks down slower too. I have a refrigerated air dryer on my air compressor, but I never fill tires with just that. Dry nitrogen always, with a dew point of like -60 degrees, for free. Oxygen, and moisture are of no benefit for tires, or wheels period.


From cylinders of compressed nitrogen ?

How do you start from "zero" with a mounted tire, how many purges and fills do you do ?

Do you provide the customers with "tire balloons" that keep their rotating assemblies free from contact with oxygen and moisture ?

I edited that. I use a N2 generator which is 4% O2, which is what the tire will equalize to, and stay there. How is wet compressed air better? I wouldn't want to try it, but could you imagine how bad it would be if a tire was filled with pure oxygen instead. It's pretty powerful stuff, and for breathing, your dead if it drops to 15% oxygen.
 
Last edited:
Originally Posted By: Traction

I edited that. I use a N2 generator which is 4% O2, which is what the tire will equalize to, and stay there. How is wet compressed air better?


Sorry, I was responding to your direct statement, before you editied it.

Now that you've allowed oxygen to be in the inside (and the outside) of the tyre, and justified that as at an equilibrium level, I'll address your "How is wet compressed air better ?" strawman....

It IS a strawman, as you are asking me to explain the benefits of water in the system.

As I've already explained, the delta P due to the change in pressure of 1% moisture in the air is negligible (well you can't measure it between 0C and 50C, so it can't be a problem) in the scheme of things, when both the Nitrogen, AND the oxygen that you see fit to install free into your customers tires aren't a problem either.

Now, it's your turn to tell us WHY it (your water strawman) is so bad...and why you don't just dry the air (with the equipment that you already have) and stop fapping around like
a) it's nitrogen (which it isn't)
b) it's magic (which it isn't)

Or is it that some rat with a gold tooth sold you some gear to make "nearly" nitrogen, and "pretty dry" ?
 
Oh, and you edited while I was typing, with another "slippery slope" strawman logical falacy.

Yes, we've seen what pure oxygen does in a space capsule with polymers...very very nasty.

But your "I can't believe it's not Nitrogen" doesn't affect the 20.9% oxygen on the outside of the tyre, plus the UV and Ozone, and other junk at tyre level in a big city.
 
Originally Posted By: Shannow
Yes, we've seen what pure oxygen does in a space capsule with polymers...very very nasty.

OMG, I remember the Apollo accident. Sitting right here at home, what a terrible thing that was...
 
Originally Posted By: Shannow
It IS a strawman, as you are asking me to explain the benefits of water in the system.

Water cooled tyres?

I suppose you'd have to establish what ethylene/propylene glycol plus all the additives does to tyre structure, but IIRC tractors sometimes use water-ballasted tyres and I assume they have to prevent freezing, which would give a lumpy ride even for a tractor, so it might not be a problem.

Ideally you'd want fins on the inside and outside of your rims.
 
Originally Posted By: Shannow
But your "I can't believe it's not Nitrogen" doesn't affect the 20.9% oxygen on the outside of the tyre, plus the UV and Ozone, and other junk at tyre level in a big city.

Cmon, we dealt with that one last week. That's what shoe polish (preferably Kiwi), or, more speculatively, sunflower oil, is for.

But I know it can be hard to keep up with the pace of punk technology progress...
 
How about filling them with carbon dioxide and getting carbon credits for sequestrating it?
laugh.gif
 
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