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Old 5th May 2009, 14:51   #436
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To put certain laws of Physics into place, before too many get misguided!

1) Nitrogen expands with temperature to EXACTLY the same extent as DRY compressed air. Both are gases and ALL gases behave the same in these respects.
2) Nitrogen does NOT cause wear of rubber tyres!!! Compressed air, if it contains much moisture will cause steel rims to rust but will have no adverse effect on alloy rims!

It is beyond debate hat if Nitrogen gives you a 'feel good' benefit you are welcome to use it.
But, PLEASE, do not try to back your claims with the laws you know little about - the laws of Physics or Chemistry!
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Old 5th May 2009, 14:53   #437
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anup is right. All gases follow the gas law P1V1=P2V2
Nitrogen will give advantage in very extreme conditions(race track) which you will not be able to replicate inhouse. Only if your driving style means your tires wear out within 500kms, you should go for nitrogen in your tires
Otherwise a little extra moisture is not going to hurt
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Old 5th May 2009, 15:52   #438
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Default The KEY is "Dry Air"

The real question is "are you filling dry air", or "are you filling air + water vapor (moisture) mixture".

Case A: If you are able to get and fill DRY air (no moisture content), then, except for the possible oxidation (due to the presence of O2) (if your metallic part can be oxidised) there would not be much difference at "domestic" speeds.

Case B: But, if you are filling a combination of air + moisture, then a number issues come into play. Two issues that I can immediately think of, are (a) the variation in partial pressures between dry air and water vapor, and (b) the variation in the co-efficient of expansion, between pure dry air and dry air + moisture combination.

Case A is closer to filling pure N2 - it has only N2 (79%) and O2 (21%). here, you need to only worry about the relative change in co-efficient of expansion (with T) between N2 and O2.

Case B is a little complicated. Here you'll have to take into account the amount of moisture that you inject into the tyre in order to reach the recommended pressure in your tyre (say P = 30 psi) - this is because dry air (molar mass 0.029 kg) (Case A) is DENSER than moist air (molar mass 0.018 kg) (Case B).

At room temperature (low speeds) the contribution of moisture will be negligible. At higher T (faster speeds), the variation to the total P, because of moisture will become significant.

If you fill N2 (Case C), then all the variables are removed - the only remaining issue being the co-efficient of expansion of N2.

If you wish to dive deeper into this, among other standard textbooks such as Resnick and Halliday, you can see:

Humid Air and the Ideal Gas Law
Density of Dry Air, Water Vapor and Moist Humid Air
Moisture in air
Dalton's law - Wikipedia, the free encyclopedia
Partial pressure - Wikipedia, the free encyclopedia
Water vapor - Wikipedia, the free encyclopedia
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Old 5th May 2009, 17:02   #439
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Quote:
Originally Posted by Tempelhof View Post
The real question is "are you filling dry air", or "are you filling air + water vapor (moisture) mixture".

Case A: If you are able to get and fill DRY air (no moisture content), then, except for the possible oxidation (due to the presence of O2) (if your metallic part can be oxidised) there would not be much difference at "domestic" speeds.

Case B: But, if you are filling a combination of air + moisture, then a number issues come into play. Two issues that I can immediately think of, are (a) the variation in partial pressures between dry air and water vapor, and (b) the variation in the co-efficient of expansion, between pure dry air and dry air + moisture combination.

Case A is closer to filling pure N2 - it has only N2 (79%) and O2 (21%). here, you need to only worry about the relative change in co-efficient of expansion (with T) between N2 and O2.

Case B is a little complicated. Here you'll have to take into account the amount of moisture that you inject into the tyre in order to reach the recommended pressure in your tyre (say P = 30 psi) - this is because dry air (molar mass 0.029 kg) (Case A) is DENSER than moist air (molar mass 0.018 kg) (Case B).

At room temperature (low speeds) the contribution of moisture will be negligible. At higher T (faster speeds), the variation to the total P, because of moisture will become significant.

If you fill N2 (Case C), then all the variables are removed - the only remaining issue being the co-efficient of expansion of N2.

If you wish to dive deeper into this, among other standard textbooks such as Resnick and Halliday, you can see:

Humid Air and the Ideal Gas Law
Density of Dry Air, Water Vapor and Moist Humid Air
Moisture in air
Dalton's law - Wikipedia, the free encyclopedia
Partial pressure - Wikipedia, the free encyclopedia
Water vapor - Wikipedia, the free encyclopedia
Just a simple question to all the technical gyan posted by you. What happens if the N2 contains 5% - 10% moisture?
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Old 5th May 2009, 17:09   #440
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Quote:
Originally Posted by vikram_d View Post
Just a simple question to all the technical gyan posted by you. What happens if the N2 contains 5% - 10% moisture?
It Cannot contain Moisture if its Pure Nitrogen. Ideally something like 99% Nitrogen.
Air on the other hand is a mixture of gases.

I however don't agree with the Nitrogen theory and in the light no significant argument in its favour, don't bother about it.

One question though.
How can air corrode the rim or any metal when its sitting trapped inside a rubber tube. (for tube type tires).
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Old 5th May 2009, 17:19   #441
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It Cannot contain Moisture if its Pure Nitrogen. Ideally something like 99% Nitrogen.
My point is that there are very very few sources of 99% pure N2. The blue commercial cylinders that we see in most of the tyre shops are not pure N2. They almost always contain 5 - 10% moisture.

And I have done enough research to figure out that N2 is absolutely not worth it.

FYI - I used to be a N2 fan once but not anymore.

To all others. I use normal compressed air and the pressure in my tyres has not dropped below what I had filled in the last 6 months. So much for N2.
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Old 5th May 2009, 17:37   #442
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Originally Posted by vikram_d View Post
To all others. I use normal compressed air and the pressure in my tyres has not dropped below what I had filled in the last 6 months. So much for N2.
Then your one of the lucky guys.

I use to check my tyre pressure every sunday and each time i see a drop of atleast 2psi when it was filled with normal compressed air.
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Old 5th May 2009, 17:57   #443
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Quote:
Originally Posted by vikram_d View Post
Just a simple question to all the technical gyan posted by you. What happens if the N2 contains 5% - 10% moisture?
If the N2 contains moisture, it is as good as filling normal air (Case B).
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Old 5th May 2009, 18:21   #444
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I use to check my tyre pressure every sunday and each time i see a drop of atleast 2psi when it was filled with normal compressed air.
That is way too much! You should have got the tyres checked for slow leaks and/or leaking valves.
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Old 5th May 2009, 18:33   #445
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Originally Posted by mobike008 View Post
Then your one of the lucky guys.

I use to check my tyre pressure every sunday and each time i see a drop of atleast 2psi when it was filled with normal compressed air.
That means that your tyre has a leaky valve or a small puncture or something.

I've been using a foot pump (atmospheric air) and a handheld pressure gauge to maintain correct tyre pressures on my cars for several years and the pressure remains constant for atleast a month - even in the ancient cross ply Ceat tyres on my Premier Presidents stay at the correct pressure for a month.

A properly fitted and puncture free tyre (if tubeless) or tyre + tube should easily go 4 weeks without the need to pump in more air.
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Old 5th May 2009, 19:09   #446
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Where do you get Nitrogen in Mumbai????? or on the highway enroute to Gujarat???
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Old 5th May 2009, 19:39   #447
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How do they ensure that the tyre is filled with100% N2? Will it not require initial 100% deflation. And will not the total deflation result in temporary deformation of the tyre and hence damage to it, especially if it is steel belted?
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Old 5th May 2009, 20:25   #448
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Originally Posted by mobike008 View Post
Then your one of the lucky guys.

I use to check my tyre pressure every sunday and each time i see a drop of atleast 2psi when it was filled with normal compressed air.
Mobike008, my car's tyres lose about 3 PSI over a month. And these are no hot rod high perf tyres but plain Jane BS Turanza ER300 OEM shoes.

You definitely had a slow leak possibly caused by an iffy tyre valve especially if you're on tubeless tyres.

Guys, I love cars, but also love my wallet. Rs 200 to fill N in your tyres is not a big deal nowadays but I am looking at it from the convenience and maintenance point of view.

Rgds,

Last edited by R2D2 : 5th May 2009 at 20:28.
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Old 5th May 2009, 20:31   #449
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Quote:
Originally Posted by anupmathur View Post
It is beyond debate hat if Nitrogen gives you a 'feel good' benefit you are welcome to use it
Hear! Hear!! This mirrors my POV.

Rgds,
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Old 5th May 2009, 20:40   #450
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Originally Posted by GTO View Post
You tell 'em, R2D2. This situation is similar to the one on MHP (mental horse power)
LOL! I am trying to!

Cheers!
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