Nitrogen in tires?

[John U.]

Thank you, I knew someone would have the answer.

[Rocketman]

Molecular weight verses atomic diameter are different.
While Nitrogen has less mass, it has a triple bond which causes the actual molecule to be larger than a double bonded oxygen pair.
O2 has a covalent radius of 66 pm where N2 has a covalent radius of 71 pm.

I have a hard time believing that 5 PICOmeters (<10%) makes a significant difference.  Not at the relative pressures we're dealing with.
The moisture makes sense, and I'm willing to listen to arguments about the heating.  Additionally, the fact that 79% of the air is nitrogen anyway kinda makes it less useful.  That's why I think the moisture is the biggest difference.
Race cars and jet planes run at much higher speeds, obviously.  What is important in race environments can be good in a city street environment, but of such a small benefit as to not make it worth even thinking about.

[SgtBunny]

I was just providing info about the difference between the N@ and O2 molecule.

I believe the heat expansion and water content are the prime factors to use Nitrogen.

The Oxidation argument I also believe is week since my tires wear out faster than they could oxidize.

[srbarclay]

Yesterday I did the nitrogen "thang" on my Valk.
I put each tire into a vacuum then inserted the nitrogen.
100% pure without any atmospheric air to corrupt the tire.
I'll run them this way for a while and then check for pressure levels and tire wear.

[XXTi]

If running nitrogen in your tires makes you feel better, by all means do it.  In reality, I don't believe it makes one bit of difference if you can find fairly dry air.

All gasses in our normal world behave very closely to the ideal gas law.  PV=nRT.  Nitrogen is not exempt from this general law.

[Farther]

The ideal gas law may not be a good application here because it doesn't deal with molecular size.  But I could be wrong, it has been almost 40 years since I took high school physics.  All things being equal, nitrogen does a slightly better job than ambiant air.  If your tire installer offers it free then it is a good deal.  If you have to search out a vender and pay more for it then it is not such a good deal.  I purchase my auto tires at Costco and they install nitrogen at no additional cost and their tire prices are better than any other dealer.  Works for me.

[XXTi]

The ideal gas law describes the relationship between pressure, volume and temperature of most gasses.  It has nothing to to with molecule size.

In my opinion, the difference between the size of a nitrogen and oxygen molecule is insignificant in this discussion.  It may be an argument for those who sell nitrogen.

As for the comment that pure nitrogen heats up slower than air, I doubt that's true either.  I'll look up the heat capacity of both when I get back to work on Monday.

[Rocketman]

As for the comment that pure nitrogen heats up slower than air, I doubt that's true either.  I'll look up the heat capacity of both when I get back to work on Monday.

Heat capacity of air (dry, at 0 deg C)=1.0035
Heat capacity of nitrogen=1.0040

Difference is less than 0.1%.  That is statistically insignificant.
Moisture would actually drive the heat capacity of air UP.

Seems like a dry air source would be indistinguishable from nitrogen in every way.

[XXTi]

Thanks for posting that.  I forgot to look it up this week.

[fudgie]

I'm trying to understand how it cools the tires? I assume, the tires warm up from the outside in. Friction. If the hydrogen atoms are 'to big' to squeeze through the rubber, then how does it cool? To me, I have seen no tire on a vehicle or bike ever get hot enough to pop. Even when cars are stuck on the ice they heat up but never to hot to pop. Take that back, burn out pits pop tires. I associate that with the tread being wore off tho.

[valkyriemc]

As for the comment that pure nitrogen heats up slower than air, I doubt that's true either.  I'll look up the heat capacity of both when I get back to work on Monday.

Heat capacity of air (dry, at 0 deg C)=1.0035
Heat capacity of nitrogen=1.0040

Difference is less than 0.1%.  That is statistically insignificant.
Moisture would actually drive the heat capacity of air UP.

Seems like a dry air source would be indistinguishable from nitrogen in every way.

Just thought abt that myself. I had a HF tuner that handles 1KW fail to tune Friday, the idiot lights indicated low pressure up on the roof. Sure enough, it normally operates on 5 psi, but indicated 2. Options are to purge and fill with nitrogen or call for the dry air pump from HQ.