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Nitrogen in Car Tires
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Apr 24, 2023 16:12:15   #
RCJets Loc: Virginia
 
As a retired airline pilot, I seem to remember some talk about large and high pressure tires in Aircraft. One of the facts mentioned was that nitrogen molecules were larger than the other elements in regular air. This being the case, it will not bleed through the tire rubber as Oxygen or some of the other gases can do. Another fact, already mentioned, is that it does not support combustion. This could be a major reason it for using it in aircraft tires, as a hot brake fire in a wheel well could be less dangerous.

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Apr 24, 2023 17:10:12   #
TriX Loc: Raleigh, NC
 
RCJets wrote:
As a retired airline pilot, I seem to remember some talk about large and high pressure tires in Aircraft. One of the facts mentioned was that nitrogen molecules were larger than the other elements in regular air. This being the case, it will not bleed through the tire rubber as Oxygen or some of the other gases can do. Another fact, already mentioned, is that it does not support combustion. This could be a major reason it for using it in aircraft tires, as a hot brake fire in a wheel well could be less dangerous.
As a retired airline pilot, I seem to remember som... (show quote)


The molecular sizes of oxygen, nitrogen and argon are 0.299, 0.305, and 0.363 nanometers (nm) respectively. Air is 78% nitrogen 21% oxygen and the other 1% trace elements such as argon. Nitrogen molecules are only 2% larger than oxygen molecules which only occupy 21% of the volume, so difficult for me to see that the molecular size makes any difference in diffusion through the tire sidewalls. I’d guess (but can’t prove) that leaks around the bead and valve stem are more significant. The absence of water and oxygen leading to corrosion, and as you mention, nitrogen not supporting combustion at high temperatures such as those encountered by airline tires seems the reason for it’s use in aircraft tires as mentioned in the post above.

If leakage through the rubber sidewalls is the real reason, Argon would be the obvious choice. In automobile tires, it’s all about preventing corrosion of the tire pressure monitoring sensors by moisture and oxygen.

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Apr 24, 2023 17:43:41   #
burkphoto Loc: High Point, NC
 
TriX wrote:
The molecular sizes of oxygen, nitrogen and argon are 0.299, 0.305, and 0.363 nanometers (nm) respectively. Air is 78% nitrogen 21% oxygen and the other 1% trace elements such as argon. Nitrogen molecules are only 2% larger than oxygen molecules which only occupy 21% of the volume, so difficult for me to see that the molecular size makes any difference in diffusion through the tire sidewalls. I’d guess (but can’t prove) that leaks around the bead and valve stem are more significant. The absence of water and oxygen leading to corrosion, and as you mention, nitrogen not supporting combustion at high temperatures such as those encountered by airline tires seems the reason for it’s use in aircraft tires as mentioned in the post above.

If leakage through the rubber sidewalls is the real reason, Argon would be the obvious choice. In automobile tires, it’s all about preventing corrosion of the tire pressure monitoring sensors by moisture and oxygen.
The molecular sizes of oxygen, nitrogen and argon ... (show quote)


My experience with TPMS sensors is that their non-replaceable batteries die before corrosion is an issue. I don't use Nitrogen in my tires.

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Apr 24, 2023 17:46:51   #
HOHIMER
 
sippyjug104 wrote:
Jerry, There is a reason why one does not want to mix the gases in their tires and it is due to Dalton’s law, which is the statement that the total pressure of a mixture of gases is equal to the sum of the partial pressures of the individual component gases. The partial pressure is the pressure that each gas would exert if it alone occupied the volume of the mixture at the same temperature.

In simple terms, each gas produces a specific pressure based on its temperature. In a mixture of gases, it means that the resulting pressure will be the sum of each of those gas's pressures. Because the tire is a confined space, those pressures will be the aggregate of the pressure of each of the gases in the tire.
Jerry, There is a reason why one does not want to ... (show quote)


So? How does that relate to the fact I fill my tires with 32 psi of Air vers. 32 psi of pure Nitrogen?

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Apr 24, 2023 17:49:53   #
petrochemist Loc: UK
 
TriX wrote:
The molecular sizes of oxygen, nitrogen and argon are 0.299, 0.305, and 0.363 nanometers (nm) respectively. Air is 78% nitrogen 21% oxygen and the other 1% trace elements such as argon. Nitrogen molecules are only 2% larger than oxygen molecules which only occupy 21% of the volume, so difficult for me to see that the molecular size makes any difference in diffusion through the tire sidewalls. I’d guess (but can’t prove) that leaks around the bead and valve stem are more significant. The absence of water and oxygen leading to corrosion, and as you mention, nitrogen not supporting combustion at high temperatures such as those encountered by airline tires seems the reason for it’s use in aircraft tires as mentioned in the post above.

If leakage through the rubber sidewalls is the real reason, Argon would be the obvious choice. In automobile tires, it’s all about preventing corrosion of the tire pressure monitoring sensors by moisture and oxygen.
The molecular sizes of oxygen, nitrogen and argon ... (show quote)


Your quite right, diffusion through the tyre wouldn't differ significantly between air & nitrogen. It would be a different matter with hydrogen, which gradually diffuses through steel, but that's not a popular choice for other reasons!

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Apr 24, 2023 17:50:40   #
TriX Loc: Raleigh, NC
 
RightOnPhotography wrote:
It is definitely not a gimmick. For the last four years, my Audi dealer fills my summer and winter tires with nitrogen every time I swap tires for the season (twice a year) and this works wonderfully. Never need to add air to my tires and I don't even remember when was the last time I had to do it. Yes, it costs $35, but my peace of mind is worth every penny.


How often do you check your tire pressure and with what gauge? A more likely explanation is since you change tires twice a year, the dealer checks and adjusts your tire pressure.

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Apr 24, 2023 17:52:44   #
Dannj
 
marine73 wrote:
Interesting about the nitrogen, the military uses nitrogen filled tires on their aircraft especially for carrier ops. It seems that nitrogen filled tires will not skid on the carrier deck. On another note I recently had to add air to a tire while on my way to work, the closet place was a costco and when I pulled up to the dispenser I read it and it said that it puts out nitrogen to fill the tires, you set the pressure for the tire and the inflation valve locks onto the valve stem. Keep in mind that this is for costco members.
Interesting about the nitrogen, the military uses ... (show quote)


Does this imply that the nitrogen affects the tread’s ability to grasp the surface?

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Apr 24, 2023 17:54:06   #
TriX Loc: Raleigh, NC
 
Dannj wrote:
Does this imply that the nitrogen affects the tread’s ability to grasp the surface?


Yep, I’m wondering about the mechanism of that also…

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Apr 24, 2023 17:55:09   #
petrochemist Loc: UK
 
HOHIMER wrote:
So? How does that relate to the fact I fill my tires with 32 psi of Air vers. 32 psi of pure Nitrogen?


It's not relevant but the partial pressure from nitrogen will be about 25psi if filled with air, and 32psi with pure nitrogen. In the case of air the remainder will be made up as 6.7psi partial pressure from oxygen & 0.3psi from the remaining gases.

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Apr 24, 2023 19:24:10   #
SteveFranz Loc: Durham, NC
 
sippyjug104 wrote:
Jerry, There is a reason why one does not want to mix the gases in their tires and it is due to Dalton’s law, which is the statement that the total pressure of a mixture of gases is equal to the sum of the partial pressures of the individual component gases. The partial pressure is the pressure that each gas would exert if it alone occupied the volume of the mixture at the same temperature.

In simple terms, each gas produces a specific pressure based on its temperature. In a mixture of gases, it means that the resulting pressure will be the sum of each of those gas's pressures. Because the tire is a confined space, those pressures will be the aggregate of the pressure of each of the gases in the tire.
Jerry, There is a reason why one does not want to ... (show quote)


Not only that, you need to be diligent every spring to change you winter air for summer air - and in the fall replace the summer air with winter air.

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Apr 24, 2023 19:52:59   #
Drbobcameraguy Loc: Eaton Ohio
 
thegrover wrote:
The air in Earth's atmosphere is made up of approximately 78 percent nitrogen and 21 percent oxygen.Sep 12, 2016


BINGO. It's a great scam. The only reason it is used in race cars is it doesn't expand as much due to heat. Lol.

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Apr 24, 2023 22:17:13   #
Flyerace Loc: Mt Pleasant, WI
 
When my vehicle hasn't been used, the tire pressure runs 34-35. Once on the road, that moves to 36-37. They stay pretty even while running. The standard on the door states the tire pressure should be 35, but they still look brand new at 37. (not a big diff, but just advising the little diff between a cold tire and a warm tire)

My car is just 1 year old this month. Just over 10,000 miles.

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Apr 24, 2023 23:05:10   #
Lucasdv123
 
I do it every 2 months. The car get 36 psi and the truck get 40 psi.we never carry any load in the truck.the old tires wore out on the sides so that is why we go to 40 psi.i use a ryobi compressor that looks like a little suitcase.you program the psi and connect it and turn it on .it will stop at the programed psi.it can also be used as a blower to blow up air beds and swimming pools.

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Apr 25, 2023 02:09:52   #
AzYooper Loc: Sun Lakes AZ (Almost Phoenix)
 
I bought a set of new Michelins for our car at Costco. (Arizona) They fill them with nitrogen, rotate them for free and have a free nitrogen pump at service center. Anyone know why they would do this? I never asked why they use the nitrogen
Anyone know?

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Apr 25, 2023 05:44:52   #
HOHIMER
 
AzYooper wrote:
I bought a set of new Michelins for our car at Costco. (Arizona) They fill them with nitrogen, rotate them for free and have a free nitrogen pump at service center. Anyone know why they would do this? I never asked why they use the nitrogen
Anyone know?


Catering to an implausible social construct that pure Nitrogen is required in tires driven in a conservative way. Race cars, maybe, but not necessary for a day to day driver. Nitrogen tends to not change the tire pressure as much (as the tire heats and cools during hard driving), as contrasted to air.

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