BAC Forum
General Boards => Technical Support => Topic started by: Jim and Carol Contratto on June 18, 2009, 02:32:39 AM
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Hi All BAC Members:
Just wondering if anyone has any information regarding Nitrogen fill in motorhome tires, if anyone has done it, are you satisfied??!!!, I have Goodyear G-70's.
Jim Contratto
06 Patriot Thunder
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From the research that I have read, there are some benefits to using nitrogen in tires. However the benefits of slightly less air loss and less tire aging and more stable tire pressure with temperture changes are only marginal. Therefore the cost and inconvenience of using nitrogen in your tires is rarely cost effective if you check your tire pressure and maintain it regularly as you should.
Gerald
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Nitrogen molecules are larger than air molecules. Therefore tires leak more slowly. Nitrogen filled tires run much cooler and as heat is a huge factor in tire wear, tires last longer.
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Jeremy,
I have never heard that nitrogen filled tires run cooler and for the life of me I cannot rationalize why that would be. I could do a google search but if you already have some insight let us know.
Thanks Ed
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I dont know about run cooler much, but are more Heat stable yes i agree.
the tires are more predicable at temeperature.
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Here's a link to the straight scoop on N2 in tires.
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=191&affiliate=HM5&s_kwcid=AL!3756!3!55250840053!b!!g!!_cat:tires&ef_id=U7hK7gAABVtQCMzP:20140728044321:s
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It would seem. To me that if Nitrogen molecules are larger that oxygen or co2 molecules, that over time, more O2 and CO2 molecules would leak out or our tires, and eventually, all we would have left would be Nitrogen anyway.
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Clearly there are some benefits to using Nitrogen in MH tires. However, I (as others on this forum) believe that the benefits do not outweigh the cost, trouble and inconvenience.
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The air we breathe, and pump into our tires, is almost 80% N.
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It would seem. To me that if Nitrogen molecules are larger that oxygen or co2 molecules, that over time, more O2 and CO2 molecules would leak out or our tires, and eventually, all we would have left would be Nitrogen anyway.
Robert, I just love your reasoning, so now I wonder if anybody has actually checked the air coming out of a tire after a couple of years.
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This is the Ford .vs Chevy
argument discussion. Just my 2 cents.
Stan
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First of all, I'm not sure where this nitrogen is larger than oxygen stuff comes from. It sure isn't related to the atomic weight of the molecule since oxygen outweighs nitrogen and is the larger atom.
As for heating, it should be noted that all gases obey the Ideal Gas Law which you might remember from chemistry class. To remind you what that is, it is:
PV = nRT
What this means is that all gases obey the same laws and essentially heat up at the same rate. So the claims that nitrogen won't heat up in a rolling tire or will heat significantly less than normal air is simply contrary to science. As tires heat up the gas in them heats and the pressure in them is subject to the following relationship:
P1T2 = P2T1 which simply means is that as the temperature increases the pressure increases also. The Ideal Gas Law simply states that all gases will obey the same rules.
I don't care if you want to spend your money filling your tires with nitrogen if it makes you feel better safer, but I thought some people might be interested in the science behind it all.
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Thanks Joel, science does add some sanity to what is sometimes folk lore. There are good reasons to keep moisture out of these tires and nitrogen sources do that but water separators on compressors also do that job pretty well. Beyond that, I think other claims are pretty marginal.
Later Ed
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This subject is always interesting. While O2 has a higher MW than N2, it is also has a smaller "effective" size due it's structure as it's electron cloud is more compact.
Also, what you are dealing with is the permeation rate (or flux) though a membrane..in this case rubber The effective permeation rate of O2 is ~3-4X that of N2. So the short answer is yes, N2 will leak down less than air. However there is a caveat here in that as O2 diffuses through the rubber the quantity of O2 decreases so less permeates and therefore the rate of change decreases with time.
From a practical point of view the change in pressure will be hardly noticeable in the short term. On the flip side O2 is quite reactive and using nitrogen will, in theory, extend the life of a tire by reducing the adverse affects of oxidation of the rubber compounds if indeed there are any.
Somewhere in my files I have a good paper on this subject I will be happy to dig up if anyone is interested.
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http://www.popularmechanics.com/cars/how-to/repair-questions/4302788 This is from Popular Mechanics
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Dick,
Thanks for the permeation information. I have posted info on this subject in the past but we have new owners on the forum and it may be good to touch upon it once again. If you look at the rubber tire structure with an electron microscope it looks porous or stranded and there would certainly be rapid air loss without the interior barrier coat on the inside of the tire. All tires have this interior barrier coating used to slow the air migration.
I live near the gulf coast and when I added air it was always humid and I paid no attention to that fact on my last coach. When I would go to check the air I would get a mist or some water droplets at the gauge and Schrader valve. I had a Michelin tire on the rear fail in my last coach and a year later I had a second one fail. I noticed where the sidewall "zipper fail" was that the steel cables looked oxidized (rusted) where they failed. I had all my tires replaced and made arrangements with Michelin to have the failed tire sent in and failure analyzed. I passed that oxidation observation onto them at the time of fail. They always assumed that the tire fail cables sat exposed and any oxidation always occurred after the fail so it was ignored in the past.
I was in the habit of checking and noting air pressure before I headed out so I had a long track record that the tires were never run under inflated. I worked with a reliability engineer at Michelin and what we surmised as a plausible fail mechanism, because in the colder months my RV sat, that under the right conditions of moisture saturated air migration through the sidewall, the moisture could condense on the steel cords. They surmised if those steel cables oxidize and the surface was roughened that they will saw themselves apart with flex and stretch cycles during rotation. They do not see this issue on truck tire use given in general they do not sit but they have noted higher failure rates in RV tire use, which they always assumed was due to improper inflation.
They have since increased the barrier coat thickness in tires in response to this possibility. I have added a water separator to a small electric compressor that I use on the road. If your coach has an air dryer then the onboard system is a good air source. So on the subject of moisture in tires, it may be one of the good reasons to consider nitrogen in RV tires if you have no other dry air source. This is a non issue in cars given there are no steel cables in the sidewalls. Something for us all to consider...especially you fogged in folks in Newport and the Florida crowd.
Later Ed
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Thanks Dick and Ed,
I feel vindicated !!
Jeremy
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I use Nitrogen in my race car tires because it doesn't expand as much as "air" when it is heated up. The tires will still heat up the same, they just don't increase in tire pressure. So be careful you might get a speeding ticket!My 2 cents... :)
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I use Nitrogen in my race car tires because it doesn't expand as much as "air" when it is heated up. The tires will still heat up the same, they just don't increase in tire pressure. So be careful you might get a speeding ticket!My 2 cents... :)
I won't belabor the point, but if you agree that the nitrogen-filled tires heat up the same as the air filled, then they will expand exactly the same amount also. There's no getting around chemistry:
PV=nRT