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#1
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Why nitrogen?
The thread on brakes raised a question from the past- why nitrogen in the
tires of big jets and heavies? Air is around 78% nitrogen anyway, and the coefficient of expansion of the remaining 20% that's oxygen can't make that much difference in volume. Why not just use dry air? I couldn't imagine that dry air or dry nitrogen could make that much difference in corrosion, either. I seem to recall someone giving me the rationale for this a long time ago, but also seem to remember thinking it didn't make that much sense at the time. |
#2
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Why nitrogen?
On Sep 15, 6:09*pm, "Viperdoc" wrote:
The thread on brakes raised a question from the past- why nitrogen in the tires of big jets and heavies? Air is around 78% nitrogen anyway, and the coefficient of expansion of the remaining 20% that's oxygen can't make that much difference in volume. Why not just use dry air? I couldn't imagine that dry air or dry nitrogen could make that much difference in corrosion, either. I seem to recall someone giving me the rationale for this a long time ago, but also seem to remember thinking it didn't make that much sense at the time. The legend is that the oxygen is reacting with the rubber. Even though compressed air has the same fraction of oxygen as does the atmosphere, the fact that it's compressed, it's been argued, increases its reactivity. I can't validate the legend. |
#3
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Why nitrogen?
On Sep 15, 6:20*pm, a wrote:
On Sep 15, 6:09*pm, "Viperdoc" wrote: The thread on brakes raised a question from the past- why nitrogen in the tires of big jets and heavies? Air is around 78% nitrogen anyway, and the coefficient of expansion of the remaining 20% that's oxygen can't make that much difference in volume. Why not just use dry air? I couldn't imagine that dry air or dry nitrogen could make that much difference in corrosion, either. I seem to recall someone giving me the rationale for this a long time ago, but also seem to remember thinking it didn't make that much sense at the time. The legend is that *the oxygen is reacting with the rubber. Even though compressed air has the same fraction of oxygen as does the atmosphere, the fact that it's compressed, it's been argued, increases its reactivity. I can't validate the legend. I got curious, did a quick check. The process also reduces water vapor, and N2 does not migrate through the rubber as fast as does O2, so pressure stays more predictable. So it's more consistent tire pressure, less corrosion. |
#4
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Why nitrogen?
"Viperdoc" wrote:
The thread on brakes raised a question from the past- why nitrogen in the tires of big jets and heavies? Air is around 78% nitrogen anyway, and the coefficient of expansion of the remaining 20% that's oxygen can't make that much difference in volume. Why not just use dry air? I couldn't imagine that dry air or dry nitrogen could make that much difference in corrosion, either. I seem to recall someone giving me the rationale for this a long time ago, but also seem to remember thinking it didn't make that much sense at the time. Consumer Reports noted: "The National Highway Traffic Safety Administration (NHTSA) has seen reduced aging of tires filled with nitrogen. Though the data does support that passenger car tires could benefit by all the claims made for nitrogen, tire manufacturers say that they already design tires to perform well with air inflation. And while nitrogen will do no harm, manufacturers say that they don't see the need to use nitrogen, which generally adds $5 or more per tire charge." From: http://blogs.consumerreports.org/car...nitrogen-.html Also CR's Q&A answers imply that if you have a lot of tires (as on a truck) then using N2 may be a net win, but probably not in other cases: "The positive benefits of nitrogen in high(er) service pressure applications, such as used in large truck tires, has been documented in the industry. Our test centered on passenger tires, only. We are not discrediting the use of nitrogen, but it is not a substitute for regular inflation checks." From: http://blogs.consumerreports.org/car...en-tires-.html |
#5
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Why nitrogen?
"Viperdoc" wrote in message
... The thread on brakes raised a question from the past- why nitrogen in the tires of big jets and heavies? Air is around 78% nitrogen anyway, and the coefficient of expansion of the remaining 20% that's oxygen can't make that much difference in volume. Why not just use dry air? I couldn't imagine that dry air or dry nitrogen could make that much difference in corrosion, either. I seem to recall someone giving me the rationale for this a long time ago, but also seem to remember thinking it didn't make that much sense at the time. My local automotive tire dealer now has signs up touting the availability of nitrogen. However, I agree with you that dry air should work about as well. The big contributor to pressure change is water--since there isn't enough CO2 in the air for its nonlinearity to be a major factor. The only difference that would make nitrogen seen really beneficial to me would be in the case of an aircraft which is kept hangared and seldom operated. Then, if the tire threads last a number of years, and the tires are sheltered from UV radiation, the inert nature of the nitrogen could be usefull. Peter |
#6
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Why nitrogen?
"Viperdoc" wrote in
: The thread on brakes raised a question from the past- why nitrogen in the tires of big jets and heavies? Air is around 78% nitrogen anyway, and the coefficient of expansion of the remaining 20% that's oxygen can't make that much difference in volume. Why not just use dry air? I couldn't imagine that dry air or dry nitrogen could make that much difference in corrosion, either. I seem to recall someone giving me the rationale for this a long time ago, but also seem to remember thinking it didn't make that much sense at the time. Well, the greasemonkies say it preserves the rubber. Having said that we go through them pretty quick and even considering retreads there wouldn't be years of exposure or anything.. Wheel fires may be another good reason... bertie |
#7
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Why nitrogen?
"Bertie the Bunyip" wrote in message
... "Viperdoc" wrote in : The thread on brakes raised a question from the past- why nitrogen in the tires of big jets and heavies? Air is around 78% nitrogen anyway, and the coefficient of expansion of the remaining 20% that's oxygen can't make that much difference in volume. Why not just use dry air? I couldn't imagine that dry air or dry nitrogen could make that much difference in corrosion, either. I seem to recall someone giving me the rationale for this a long time ago, but also seem to remember thinking it didn't make that much sense at the time. Well, the greasemonkies say it preserves the rubber. Having said that we go through them pretty quick and even considering retreads there wouldn't be years of exposure or anything.. Wheel fires may be another good reason... bertie Right, they are called Napoleon tires. You heard of "Napoleon Blown Apart" haven't you. :-) -- Regards, Bob F. |
#8
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Why nitrogen?
It all sounds like BS to me- if it's the tire we're discussing, there's no
contact with the nitrogen, just the inner tube. The outer surface of the tire is in air of course, along with exposure to UV light, salts, etc. The tire is going to lose its rubber well before it starts to oxidize and crack. A tube perhaps might be more subject to oxidation, but it's dark in there, not a lot of UV to make stuff that cause oxidation like free radicals and ozone, and the increase in the partial pressure of oxygen at 200psi is only around 15fold, or from around 140mm Hg to around 2000mm. If it'sdry air, I can't believe it would make that much difference. Need to see the aging data on rubber kept in air versus nitrogen. Just realized I was starting to sound like you know who, so will stop this and have another cocktail. |
#9
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Why nitrogen?
"Bob F." wrote in
: "Bertie the Bunyip" wrote in message ... "Viperdoc" wrote in : The thread on brakes raised a question from the past- why nitrogen in the tires of big jets and heavies? Air is around 78% nitrogen anyway, and the coefficient of expansion of the remaining 20% that's oxygen can't make that much difference in volume. Why not just use dry air? I couldn't imagine that dry air or dry nitrogen could make that much difference in corrosion, either. I seem to recall someone giving me the rationale for this a long time ago, but also seem to remember thinking it didn't make that much sense at the time. Well, the greasemonkies say it preserves the rubber. Having said that we go through them pretty quick and even considering retreads there wouldn't be years of exposure or anything.. Wheel fires may be another good reason... bertie Right, they are called Napoleon tires. You heard of "Napoleon Blown Apart" haven't you. :-) groan! A guy i used to work with witnessed the aftermath of someone trying to fill a 707 nosewheel wiht an incorrect type reduction on the bottle. The guy was pretty much vaporised. My friend spent months as a witness in the subsequent lawsuit. Bertie |
#10
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Why nitrogen?
"Viperdoc" wrote in
: It all sounds like BS to me- if it's the tire we're discussing, there's no contact with the nitrogen, just the inner tube. The outer surface of the tire is in air of course, along with exposure to UV light, salts, etc. The tire is going to lose its rubber well before it starts to oxidize and crack. Yeah, I kinda thought that myself which gave me the notion that the fire thing wiht heavies might be more relevant we run anything up to 300PSI as well, which might be a factor. I must ask around again. Bertie |
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