[Jiro]

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.

[jdurg]

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.  

[Jiro]

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

[Borek]

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...

[Jiro]

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.

[Mitch]

Might as well fill them with Helium, so that your car can weigh less!

[Borek]

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.

[Dude]

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.

[jdurg]

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).

[Borek]

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).

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 17^th - Oct 17^th 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

[hmx9123]

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.

[Borek]

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.

[jdurg]

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 17^th - Oct 17^th 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.

[Borek]

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  

[constant thinker]

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.