Contributor
Didn't know that....but (after reading a little bit)... THIS >>> https://www.tirebuyer.com/education/nitrogen-vs-airOriginally Posted by Dick Strauss
Takeaway: negligible difference for the typical car owner.
But if you still want it, don't pay the dealer...cheaper to join Costco...you get the nitrogen AND all the two-fers besides
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Most of our local tire dealers offer nitrogen fills as part of their standard installation package (~$20/tire for mounting/balancing). It is not worth paying for but it is nice to have.
I think the nitrogen fills may tend to make your tires last longer because nitrogen is inert while oxygen is very reactive.
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The tire inflation stations I assume are for anyone to use even if they didn't buy their tires there. Heck, someone doesn't have to even be a member to use them it looks like. Costco may have inflated any tires for free before, but if they did so before I had never heard of it and probably most members had not.
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Brian, they've only put in the nitrogen fill "parking spots" in recently at many of the stores. Prior to that, it was only available "in the bays" as part of install. I have not looked clost at the fill stations to see if there is any "member verification" or not, but I honestly suspect not.
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Nitrogen in tires is essentially a scam.
Here's an analysis of it, with some spicy language: https://autoexpert.com.au/posts/top-...elp-your-tyres
And another one. The mention of the Consumer Reports test is illuminating: https://www.lesschwab.com/article/ti...er%20vehicles.
But let's do a quick mathematical analysis:
Air is 78% nitrogen, and 21% oxygen. The nitrogen selling people say that air leaks out of tires faster than nitrogen. But that must mean that it's the oxygen leaking out, not the nitrogen. So let's say 10% of the oxygen leaks out (a very high estimate). So you refill your tire with air (of which 78% is nitrogen). Now you have a tire with 83% nitrogen. Let's say you fill your tire again 2 months later - now it's filled with 89% nitrogen. After a third filling, 95% nitrogen. So, after a few tire fillings, your tire is essentially filled with 100% nitrogen for free.
A little simplistic, but this does show that this is entirely bogus nonsense to get your money.
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Okay, so you buy new tires. They are installed on the rims and filled with nitrogen. Remember tires are hollow, so there is air inside when they are mounted. Did they pull a vacuum on the tires at any point to remove the initial air that was in it? Probably not, it would take additional special equipment. Did they purge the tires for a period of time or fill and release the pressure multiple time using only pure nitrogen to pressurize the tire each time? Probably not, that would take a lot of time and use nitrogen.
Ergo filling tires with nitrogen is a waste of time, money and effort. Just ask them to fill your tires with 78% nitrogen instead.
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I have heard the real advantage of nitrogen fill is they are using dry gas not water soaked air. Claim is many self serve air stations do not have much for a air dryer and no one drains it after it is full. What about Helium fill to reduce unsprung weight or maybe hydrogen for even more noticeable effect if it leaks out onto the hot exhaust pipe
Bill D
Contributor
Just guessing, but I think helium is more expensive than nitrogen
"What you see and what you hear depends a great deal on where you are standing.
It also depends on what sort of person you are.”
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You'd never be able to keep helium in your tires.
Confidence: The feeling you experience before you fully understand the situation
BS. Nitrogen is a single atom, Oxygen is two atoms. i.e. N vs O2. Oxygen is just slightly less than double the size molecule and permeates slower than just nitrogen. It is a bogus way to charge you Big dollars.
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Nitrogen commonly (actually overwhelmingly) exists as N2, a two atom molecule, same as Oxygen.
An N2 molecule is slightly larger (3%) than an O2 molecule.
Last edited by Patty Hann; 06-19-2023 at 11:25 AM.
"What you see and what you hear depends a great deal on where you are standing.
It also depends on what sort of person you are.”
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We just bought a new car for my wife after spending several days visiting dealerships and shopping on line. I have always felt that car salesmen (and real estate people were liars). After talking to several salesmen my opinion was confirmed. Generally by the time they had finished their second sentence they had lied. Not a single one was completely honest.
Car dealers have acquired remarkable skills when it comes to inserting scam fees into the transaction. None of the people we talked to were older than 35 so the tradition will continue. the other thing--these guys didn't know their product.
whoever commented that inventories were sparse was on the mark as far as St. Louis is concerned.
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I've heard the dry gas aspect is the reason Nitrogen is used on airplane tires, specifically on airplanes that operate at high altitudes. Tires that are repeatedly filled with moist air can accumulate a little water. When they spend time in below freezing temperatures that water is going to freeze. If the destination is near or below freezing that ice will not thaw and the tire is now unbalanced. I don't know how true that is but I do know that Michelin at least calls for Nitrogen. I can believe that an unbalanced small diameter tire going from 0 to 120 mph in the blink of an eye is not optimum.
Contributor
Physical Chemistry Professor (and former autocross racer) here.
There is a lot of voodoo about nitrogen in tires. In normal auto tires, it won't make a lick of difference. In some specific applications it makes a little difference (really small difference).
Nitrogen is a diatomic gas N2 two nitrogen atoms bonded. The atomic radius of a Nitrogen atom is 65 picometers (a pm is 10-12 meters) the molecular mass of an N2 molecule is about 28 g/mol
Oxygen is also a diatomic gas O2 two oxygen atoms bonded. The atomic radius of an Oxygen atom is 60 picometers. The molecular mass of an O2 molecules is about 32 g/mol
Dry air is about 78% nitrogen, 21% oxygen and about 1% other gases.
So nitrogen is slightly larger, so if there is a pore size effect it might leak out slower, but since it is lighter it is moving about 7% faster than the smaller (but heavier) O2 molecule which means it will find the pores that much quicker. My guess it is going to be a wash between those.
The moisture content is one area where there is a clear difference (but still probably not enough to be anything to care about except in special applications)
The comparison here is air from a compressor, and nitrogen from a gas cylinder.
The nitrogen from the gas cylinder is inherently dry (if you want super dry nitrogen, use the boil off from a liquid nitrogen tank which is at about -196 oC or -320oF so any water would be a solid )
Air from a compressor will have the partial pressure of water related to the temperature in the tank. So if the compressor tank is full and has time to cool to room temperature it will contain about 20 torr of water vapor (about 0.4 psi)) which in the vapor phase is not a big deal, it acts as a gas just like nitrogen. Where the issue is if it is not allowed to cool until it is in the tire. Say the air in the compressor tank reached 100F, theat would have about 56 torr (about 1 psi) of water. When the tire cools to room temperature about 36 torr of the vapor will condense to liquid. The liquid will add pressure based on the temperature of the tire (it will evaporate until it hits the vapor pressure of the water at the temperature of the tire). The application where this can be an issue is on racing slicks. Some of those types of tires can run maybe 15 psi so a change of 0.5 psi can be a big deal in performance (I raced in a stock class so I am not a slick expert)). Now to be clear this is on top of the approximate 7% pressure change just from the temperature change. Slicks are a pretty niche case here.
The other use case for nitrogen is aircraft tires. The FAA mandates dry nitrogen for commercial aircraft tires. FAA CFR final rule Federal Register: February 26, 1993 (Volume 58, Number 37)] [Page 11778] "SUMMARY: This amendment to the Federal Aviation Regulations (FAR) requires that an inert gas, such as nitrogen, be used in lieu of air, for inflation of tires on certain transport category airplanes. This action is prompted by at least three cases in which the oxygen in air-filled tires combined with volatile gases given off by a severely overheated tire and exploded upon reaching auto-ignition temperature. The use of an inert gas for tire inflation will eliminate the possibility of a tire explosion." If you read the FAA rule document auto-ignition temperature with air was around 500F, with nitrogen greater than 95% it was greater the 670F.
In normal automotive applications, probably not likely to get the tires that hot. (except for some of the yo-yos doing burnouts to combustion... but they want the fire)
The purpose of nitrogen in normal automotive tires is the separate you from your money.
John
Contributor
good chemistry lesson ...and excellent "takeaway" ...thanks for posting it
"What you see and what you hear depends a great deal on where you are standing.
It also depends on what sort of person you are.”
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