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General Forums => Generic Discussion => Topic started by: Jiro on June 09, 2005, 07:05:36 PM

Title: Nitrogen vs Air For Tyres
Post by: Jiro on June 09, 2005, 07:05:36 PM
Its pretty interesting that more and more people are inflating there tires with about 95% nitrogen/air in their tires today. I haven't really looked into it yet but just from comments i gathered from car enthusiasts i can see the benefits though not yet confirmed... such as:

"tire pressure does not change or fluctuate with temperature such as nitrogen.. Nitrogen does fluctuate but not as much as air." That would make for more consistent car handling characteristics I believe.

or

"nitrogen have bigger molecules. if i am wrong,, please correct me.. they dont to "leak" out of the rubber as often as regular " air " ."

or

"it just makes the tire last longer...tires break down over time when exposed to just regular air, when exposed to pure or atleast 95% nitrogen the tire lasts ALOT longer and is much more resistant to breaking down.. its good for racing because the tire doesnt lose its pressure as easily as it does with regular air"

or

"regular air has a lot of other gases (oxygen/nitrogen/etc). so it will be inconsistent/unpredictable(?) when loaded with pressure and heat."

or

"its a proven fact that nitrogen holds its pressure better then regular air "

hehehe coool.
Title: Re:Nitrogen in Tires
Post by: jdurg on June 09, 2005, 07:10:42 PM
Heh.  Nearly ALL of that is pure rubbish and funny to read since air is about 78% nitrogen.  Perhaps the ONLY quote there that could possibly have ANY merit to it is;

"it just makes the tire last longer...tires break down over time when exposed to just regular air, when exposed to pure or atleast 95% nitrogen the tire lasts ALOT longer and is much more resistant to breaking down.. its good for racing because the tire doesnt lose its pressure as easily as it does with regular air"

Chemically, it may be true that a tire filled with pure nitrogen and no oxygen may not chemically break down as easily.  Still, the 'breaking down' wouldn't be very noticeable anyway, and if you were worried about chemical activity, then you'd certainly be filling your tired with argon.   ;D
Title: Re:Nitrogen in Tires
Post by: Jiro on June 09, 2005, 07:41:28 PM
ya...tires are a different science all on thier own... lol when tires are made they have an iner liner made with antioxidants, over time they get used up and if you use regular air, the oxygen in the tire (about 21% in regular air) begins deterioration. so if you use 95+% nitrogen you eliminate a large amount of that oxygen thats left in the tire that would be eating away the tire once the antioxidants have been used.. as well, when you use regular air and you race, most ppl have to reinflate every now and again thus only feeding more oxygen into thier tires with no antioxidants, your tires wear out exponentially.. but to a regular person this means nothing, to someone who races hard, this is a big deal
Title: Re:Nitrogen in Tires
Post by: Borek on June 09, 2005, 07:48:29 PM
I have read somewhere (but kill me I don't remember where) that in fact oxygen leaves tires faster then nitrogen due to the way it interacts with the rubber (is it a proper word?). However, if that is the case after few pressure checks you have already mostly nitrogen in the tire...
Title: Re:Nitrogen in Tires
Post by: Jiro on June 10, 2005, 02:57:50 AM
the science behind using nitrogen in your tires isnt chemistry,

its marketing!!

yeah, i saw those advertisements on teh back of the buses saying that some tire shop will fill your new continental tires with 99.9% pure nitrogen. sounds impressive huh.
Title: Re:Nitrogen in Tires
Post by: Mitch on June 10, 2005, 04:22:17 AM
Might as well fill them with Helium, so that your car can weigh less!
Title: Re:Nitrogen in Tires
Post by: Borek on June 10, 2005, 06:48:28 AM
Might as well fill them with Helium, so that your car can weigh less!

No. You will have to pump them every mile. Helium leaks from everything like hell.

Have you heard about experiment Precontinent 3? Group of divers spent several weeks at about 100 meters below sea level (it was back in sixities IIRC). They breathed He/O2 mixture. On decompression all waterproof watches exploded - they were filled with helium.
Title: Re:Nitrogen in Tires
Post by: Dude on June 10, 2005, 08:13:10 AM
As JDurg mentioned, most of the information about alternative gases in tires in nonsense.  There is a slightly reduced weight (on the order of less than one pound in all four tires-a straighforward calculation using an ideal gas law is applicable) using helium, however, that extremely slight weight improvement comes with a high permeability through the polyisobutylene tire inner liner.  Compressed air (at about 35 psi) will lose about 1-2 psi per month.  Helium will lose on the order of 10 psi per day.  The heat buildup INSIDE the tire (remember that rubber is an insulator) is not sufficient to promote signficant oxidation.  There is no benefit to using nitrogen.
Title: Re:Nitrogen in Tires
Post by: jdurg on June 10, 2005, 09:22:34 AM
No. You will have to pump them every mile. Helium leaks from everything like hell.

Have you heard about experiment Precontinent 3? Group of divers spent several weeks at about 100 meters below sea level (it was back in sixities IIRC). They breathed He/O2 mixture. On decompression all waterproof watches exploded - they were filled with helium.

Actually, that's a standard mixture used for deep sea diving.  Helium is far less soluble in the blood than nitrogen is, especially at high pressures.  (Such as you would find in deep sea diving).  By replacing the nitrogen in the air mixture with helium, you can prevent nitrogen from dissolving in the blood and then 'escaping' as you rise to the surface.  (A VERY painful condition known as 'The Bends').  The presence of Helium in place of Nitrogen GREATLY reduces the incidences of this painful condition.

As for the exploding watches, that really makes absolutely no sense.  The only way that would be possible is if the watches were filled with Helium while under the water.  In order to be waterproof, there has to be absolutely no way for water to seep into the watch.  The only way the watches could explode would be if they were decompressed faaaaaaar lower than normal atmospheric pressures, and in that case the people wearing the watches would not fare too well.  (Since the watches were filled with the gas above sea level, they would be filled to approximately normal atmospheric pressure.  If the divers went far enough below sea level, then the watches could implode due to the high external pressure).
Title: Re:Nitrogen in Tires
Post by: Borek on June 10, 2005, 10:52:25 AM
Actually, that's a standard mixture used for deep sea diving.  Helium is far less soluble in the blood than nitrogen is, especially at high pressures.  (Such as you would find in deep sea diving).  By replacing the nitrogen in the air mixture with helium, you can prevent nitrogen from dissolving in the blood and then 'escaping' as you rise to the surface.  (A VERY painful condition known as 'The Bends').  The presence of Helium in place of Nitrogen GREATLY reduces the incidences of this painful condition.

Yes and no. Helium dissolves in blood as any other inert gas does and fast decompression with the blood saturated with helium is just as dangerous as when you breath air. AFAIK helium mixtures are used to avoid nitrogen narcosis (AKA rapture of the deep AKA inert gas narcosis) - as heliox by pros and trimix by amateurs (from what I heard due to price mostly).

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As for the exploding watches, that really makes absolutely no sense.  The only way that would be possible is if the watches were filled with Helium while under the water.  In order to be waterproof, there has to be absolutely no way for water to seep into the watch.  The only way the watches could explode would be if they were decompressed faaaaaaar lower than normal atmospheric pressures, and in that case the people wearing the watches would not fare too well.  (Since the watches were filled with the gas above sea level, they would be filled to approximately normal atmospheric pressure.  If the divers went far enough below sea level, then the watches could implode due to the high external pressure).

You didn't get it. Durings the month (Sep 17th - Oct 17th 1965) spent under 10 atm pressure helium - with its high permeability, low viscosity etc - diffunded into the watches. They were waterproof, not heliumproof ;) After the experiment ended and the divers were decompressing deocompression was too fast for helium to slowly leave the watches, thus they exploded - they were built to survive external pressure, not internal.

This strory is cited in the book "Nouvelles plongees sans cable" by cmd. Philippe Taillez, one of the close coworkers of Jacques Cousteau, so that's not a source that can be easily neglected. Sorry for the French title, I have the book in Polish and I suppose it will be easier to locate using the original title than the Polish one - in fact French edition has over 800 hits in google
Title: Re:Nitrogen in Tires
Post by: hmx9123 on June 10, 2005, 01:41:35 PM
I agree with judurg and borek--I'm sure the watches did explode from helium pressure, but the story still makes no sense.  They were not normal diving--they had to have been inside a diving vessel of some sort like a submarine.

Anyway, I think we should fill tires with mercury.  Prevent all that nasty seepage. :)
Title: Re:Nitrogen in Tires
Post by: Borek on June 10, 2005, 02:11:12 PM
I agree with judurg and borek--I'm sure the watches did explode from helium pressure, but the story still makes no sense.  They were not normal diving--they had to have been inside a diving vessel of some sort like a submarine.

Please read carefully my posts. They spent a month at 100 meters. And yes, they have been in a specially built habitat (that's how French called the metal sphere built for divers :) ). Whole experiment was one of milestones in the history of diving.
Title: Re:Nitrogen in Tires
Post by: jdurg on June 10, 2005, 02:40:07 PM
Yes and no. Helium dissolves in blood as any other inert gas does and fast decompression with the blood saturated with helium is just as dangerous as when you breath air. AFAIK helium mixtures are used to avoid nitrogen narcosis (AKA rapture of the deep AKA inert gas narcosis) - as heliox by pros and trimix by amateurs (from what I heard due to price mostly).You didn't get it. Durings the month (Sep 17th - Oct 17th 1965) spent under 10 atm pressure helium - with its high permeability, low viscosity etc - diffunded into the watches. They were waterproof, not heliumproof ;) After the experiment ended and the divers were decompressing deocompression was too fast for helium to slowly leave the watches, thus they exploded - they were built to survive external pressure, not internal.

This strory is cited in the book "Nouvelles plongees sans cable" by cmd. Philippe Taillez, one of the close coworkers of Jacques Cousteau, so that's not a source that can be easily neglected. Sorry for the French title, I have the book in Polish and I suppose it will be easier to locate using the original title than the Polish one - in fact French edition has over 800 hits in google


Ahhhh.  Okay.  That part about them spending weeks inside a single container which had the pressurized helium in there was missing from the first post.  I incorrectly assumed that they were using breathing apparatuses which is why I wondered how the helium got into the watches.
Title: Re:Nitrogen in Tires
Post by: Borek on June 10, 2005, 04:39:26 PM
Ahhhh.  Okay.  That part about them spending weeks inside a single container which had the pressurized helium in there was missing from the first post.  I incorrectly assumed that they were using breathing apparatuses which is why I wondered how the helium got into the watches.

I wasn't precise enough  >:(
Title: Re:Nitrogen in Tires
Post by: constant thinker on June 11, 2005, 11:28:45 PM
Doesn't that kind of diving have a name. It's called saturation diving I believe. The "habitat" remains connected to a ship and every night the pull it up replace the air tanks for diving and habitat and then drop it in the morning. The divers will spend a month or so working underwater.
Title: Re:Nitrogen in Tires
Post by: Borek on June 12, 2005, 03:53:36 AM
It's called saturation diving I believe.

Yes.

Quote
The "habitat" remains connected to a ship and every night the pull it up replace the air tanks for diving and habitat and then drop it in the morning.

It doesn't seem a good idea to me. It must be anchored at the sea bottom and it is not an easy or safe procedure to pull it up and down on a daily basis. Much easier is to send supplies in a metal basket.
Title: Re:Nitrogen in Tires
Post by: Ashi_Starshade on July 21, 2005, 02:22:29 PM
HMmm... I think that it's this reason:
"tire pressure does not change or fluctuate with temperature as much with nitrogen"

It certainly does seem to me that nitrogen would be much closer to an ideal gas than air alone, and it may be that the pressure increases more rapidly with temperature for air.

Howstuffworks.com says that (at least for professional race cars) it's to prevent pressure from evaporation of small amounts of condensed water.  But even if you filled a tire with nitrogen, if it already had water adsorbed in the inner tube, it would still be adsorbed there?  Plus, even if this were the reason, one could use anhydrous air - which is still cheaper than nitrogen (I think).

Title: Nitrogen vs. air for tires
Post by: Maury on April 11, 2006, 09:27:29 PM
Nitrogen vs. air for tires

I have seen dry nitrogen being recommended for inflating automobile tires instead of air.  Reasons given are:
1. Air's 21% oxygen deteriorates the tire, while nitrogen is inert.  I can accept this, since I believe that oxygen under pressure and at elevated temperatures accelerates oxidation.
2. Oxygen in air plus moisture in air cause corrosion of metallic parts of the wheel.  This, too, seems reasonable.
3. Nitrogen does not penetrate the tire walls as readily as oxygen and so maintains proper pressure longer.  This I do not understand.  The molecular weight of nitrogen is 28 and that of oxygen 32.  Is the size of the nitrogen molecule *larger* than that of oxygen?  It must be so, since the two gases are separable by the use of a semipermeable membrane.  But it just doesn't seem logical to me.
4. Nitrogen-filled tires run cooler than air-filled tires.   How can this be?  Is nitrogen a better "thermal conductor" than oxygen, thus permitting heat from flexure of the tire's sidewalls to be conducted to the metal hub and dissipated by outside air?

If these are not an appropriate questions for this forum, would you kindly direct me to a more suitable one?
Title: Re: Nitrogen vs. air for tires
Post by: mike on April 11, 2006, 10:34:07 PM
Quote
1. Air's 21% oxygen deteriorates the tire, while nitrogen is inert.  I can accept this, since I believe that oxygen under pressure and at elevated temperatures accelerates oxidation.

I have never seen a tyre that has oxidised all the way through from the inside to destroy the tire. I think my tread always wears out faster, LOL.

Quote
2. Oxygen in air plus moisture in air cause corrosion of metallic parts of the wheel.  This, too, seems reasonable.

So what about the rest of the car? Are people only worried about the metal inside their tyres? ::)

Quote
3. Nitrogen does not penetrate the tire walls as readily as oxygen and so maintains proper pressure longer.

Who says? If anything this would be good as the concentration of oxygen would decrease compared to nitrogen ;)

Quote
Nitrogen-filled tires run cooler than air-filled tires.

I doubt it. Nitrogen and oxygen would have similar conductance. If there is any difference it would be between dry gas and wet gas as the conductivity of water would be different.

I am happy to fill my tires with "air" rather than "dry nitrogen", how pure is "dry nitrogen" anyways?



Title: Re: Nitrogen vs. air for tires
Post by: pantone159 on April 11, 2006, 10:57:00 PM
how pure is "dry nitrogen" anyways?

I'm sure it's at least 75% pure.   ;)
Title: Re: Nitrogen vs. air for tires
Post by: Mitch on April 12, 2006, 12:33:26 AM
You have a semipermeable membrane with no oxygen inside the tire. I'll be more interested in knowing how long it takes a tire to come into concentration equilibrium with the outside air. Less than a day would be my best guess.

Yes, I agree statement 3 is screwy and if true than Mike's comment would mean there is no need for their product.
Title: Re: Nitrogen vs. air for tires
Post by: Borek on April 12, 2006, 02:56:28 AM
3. Nitrogen does not penetrate the tire walls as readily as oxygen and so maintains proper pressure longer.  This I do not understand.  The molecular weight of nitrogen is 28 and that of oxygen 32.  Is the size of the nitrogen molecule *larger* than that of oxygen?  It must be so, since the two gases are separable by the use of a semipermeable membrane.  But it just doesn't seem logical to me.

Not only size matters. O2 particles are different from N2 particles and they penetrate through the rubber much faster. Interestingly CO2 is even faster - faster then He!

http://www2.dupont.com/Vamac/en_US/assets/downloads/vamac_gas_permeability.pdf
http://www2.ubu.es/quim/quimorg/polimeros/trab_pub/gas-meg.pdf

And some reasonable IMHO comments on nitrogen in tyres:

http://www.buyrite-tyres.co.uk/tyrecare-source.html
http://www.bridgestone.com.au/tyres/products/car/care/nitrogen.asp

This subject was discussed to death several times in my presence on different chemical forums. Apart from what laymans (and nitrogen sellers) say, most chemists taking part in theses discussions agree that apart from some highly specialized areas (F1, jet tyres) use of nitrogen is a waste of money.

Most interesting comment I have seen stated that liquid nitrogen is a byproduct in some processes and it must be used somehow ;)
Title: Re: Nitrogen vs. air for tires
Post by: mrdeadman on May 08, 2006, 06:41:43 PM
i don't think it really matters, air is made up of mostly nitrogen anyway and your reasoning will just make people lazy. :P
Title: Re: Nitrogen vs. air for tires
Post by: syko sykes on May 09, 2006, 07:17:21 PM
3. Nitrogen does not penetrate the tire walls as readily as oxygen and so maintains proper pressure longer. This I do not understand. The molecular weight of nitrogen is 28 and that of oxygen 32. Is the size of the nitrogen molecule *larger* than that of oxygen? It must be so, since the two gases are separable by the use of a semipermeable membrane. But it just doesn't seem logical to me.
Oxygen molecules are larger than nitrogen molecules despite the increase in mass. This is because the valence electrons on each molecule experience the same amount of shielding because of their location but the Oxygen atom has an extra proton attracting the electrons to the center of the atom and therefore making the atom smaller. This principle explains why atoms on the periodic table typically decrease in size (radius) as you move from left to right.

how pure is "dry nitrogen" anyways?

I'm sure it's at least 75% pure. ;)

i would hope it's more than 75% pure because air naturally consists of about 78% Nitrogen deeming it useless to use dry nitrogen as a replacement.
Title: Re: Nitrogen vs Air For Tyres
Post by: billnotgatez on August 01, 2006, 08:35:57 AM
http://news.yahoo.com/s/ap/20060731/ap_on_bi_ge/nitrogen_tires

just when you think you have heard it all
Title: Re: Nitrogen vs Air For Tyres
Post by: Borek on August 01, 2006, 08:44:20 AM
just when you think you have heard it all

Note how those commercially interested speak about benefits, while those not commercially interested doesn't offer any definitive opinion ("The National Highway Traffic Safety Administration has no opinion" & "Tire experts at Consumers Union, publisher of Consumer Reports magazine, neither endorse nor object to the use of nitrogen in tires").
Title: Re: Nitrogen vs Air For Tyres
Post by: constant thinker on August 01, 2006, 11:02:53 PM
Hey for a tire company it could be a great gimmick. A reason to charge extra for something that costs them very little over what it costs them now. That's the whole notion behind super sizing foods at fast food.
Title: Re: Nitrogen vs Air For Tyres
Post by: billnotgatez on August 02, 2006, 12:58:15 AM
It is interesting that the FAA condones the use of nitrogen in commercial aircraft tires.
Title: Re: Nitrogen vs Air For Tyres
Post by: Borek on August 02, 2006, 04:53:16 AM
It is interesting that the FAA condones the use of nitrogen in commercial aircraft tires.

AFAICT they go at much higher speeds and thus much higher temperatures than average car, plus they get cooled to -40 deg C every time plane gets high enough. These are not standard conditions, I suppose that's what makes the difference. But that's only my guess.