Well, sure, if you want to sound like Donald Duck discoursing on the Existence of God. 
I will say this one more time; the loads, pressures, temperature variations, and basic construction of tires used in commerical aircraft are completely different that those used in automotive applications, including high speed racing and heavy haul cargo. In aircraft applications, users have to be concerned about undetected damage to the tire and shock-induced combustion (“dieseling”) within the tire causing failure upon a hard landing, and the subsequent loss of stability and potential for damage to delicate landing gear and the unprotected undercarriage of the aircraft as well as shrapnel being inducted into the turbines. None of this is a practical concern for passenger automobile applications where the most dangerous scenario is a sidewall blowout, or a cargo hauler where tread failure is most common.
I have provided objective evidence, maintenance information from an aircraft tire manufacturer highlighting the differences between automotive and aircraft tire applications, and basic physics of tire inflation and failure modes. You have provided nothing but insinuation and errant speculation. You have ignored repeated requests to provide anything like evidence of any actual accident or injury as the result of these incredible exploding tires that you suggest are the result of inflation with atmospheric air. There is no indication that any recognized authority (SAE, IIHS, NHTSA) has promoted pure gaseous nitrogen as prefereable on a safety bases, nor that any legislative or regulatory body has attemtped to legislate or require the use of gaseous nitrogen as a necessary and prudent safety measure in passenger automobiles. You are either patently dishonest, severely misguided, or more likely both, in your dogged pursuit of this position.
Stranger
I would just like to add that I have been near car fires and I have never seen a tire explode. Melt yes, explode, no.
I’ve been present when two different cars were burning, and both times, the tires “exploded.” The first had those big ol’ mudding tires, the other had normal sized tires. They “exploded” by producing a loud pop! and then sagged to the ground like a flat tire. There was no fireball. There was no increase in combustion. There was no shrapnel. Women and children were not evacuated from the vicinity. The tires stayed on the rims and there was no visible damage to the tire.
I actually saw an overheated tire explode where a brief flash of orange flame was produced. It lasted a very short fraction of a second and extinguished. There was sort of a soft “whoomph” sound.
I would guess, then, that you saw what I calculated above in post #39. I imagine whether or not an exploding tire produces a flame depends on how it is heated, for how long and the composition of the rubber. With a N of 4, I think we can say that data suggests that exploding automobile tires do not significantly contribute to a car already on fire. More study is needed, though. SO WHO’S UP FOR SETTING INFLATED TIRES ON FIRE!!!???
I suggest asking the French. I hear setting cars on fire is very popular over there. They must have lots of data.
I think Mythbusters tested exploding tires once, and they, too, found that tires under stress will rupture first, releasing the gas, instead of exploding.
Except for old butane Fix-A-Flat formulas and fools who weld on rims with mounted tires (with a posthumous nod to the Darwin Award nominee who did BOTH), actual automotive tire explosions are probably quite rare.
I’m just talking about the difference between releasing a pressurized burst of explosive gasses when the tire fails (even without the containment and internal ignition required for an explosion) compared to merely releasing more flammable gasses into the combustible gas rich environment of a car fire – basically the same difference as using a lit match to pop a balloon filled with acetylene and air or popping one filled with acetylene and nitrogen - the same combustible gas energy is released much more rapidly and violently when pre-mixed with oxygen, generating more heat and pressure to intensify and accelerate your car fire.
This demo has a good example of the explosive gasses that a severely overheated, air filled tire generates (Tire Explosion - YouTube) although the physics differ from a car fire since the rim is the heat source for generating the gasses and the ignition source (the temperature gauge shows a few seconds of internal combustion before sufficient temperature, heat and gas volumes build to explode).
I don’t know if the loud bangs reported at car fires are just pinhole failures allowing ignition to propagate inside the partial containment of the tire or if it’s possible for a high quality tire and a thermally conductive aluminum rim to actually explode, but I do know (as per the FAA) that keeping the inflation gas oxygen level at 5% or less never generates an explosive mixture and eliminates the possibility of either one.
On the car board that I’m on beat nitrogen to death. Basically it came down to this there is a small benefit from using nitrogen, but unless filling the tires with nitrogen was free or less than a buck or two, it wasn’t worth it for the average driver. If you race cars or engage is some kind of high stress, high temp driving there basically no benefit to you. You also have to remember that when filling a tire with nitrogen it must be done correctly to get the benefits, the tire must be filled and emptied several times to purge as much air as possible out of the tire, and even then some plain old air will remain. If they just mount the tire and fill it with nitrogen, the tire is NOT considered filled with nitrogen. And even if you managed to get all the air out of a tire oxygen will migrate it’s way back into the tire.
The point of less pressure loss overtime is true but it doesn’t stop pressure loss and you will lose pressure so you still need to check your tires.
They use it in aircraft, NASA, NASCAR so it must be good argument. As has been point out aircraft, NASA, NASCAR have different loads placed on their tires and falls into the high stress high temp exception. But a car isn’t an aircraft, NASA isn’t using it in their car tires, and odds are you’re not driving a NASCAR. Just because it good for a aircraft or whatever doesn’t make it good for you. Did you know for example that some hoses used on aircraft don’t meet DOT standards for cars and aren’t supposed to be used on cars? Should they then not be allowed on aircraft, even though they are far stronger than anything used on a car. If I remember right the aircraft hose fail during the “whip-resistance” test. But that doesn’t mean it a bad hose it just means it should be used on cars according to the DOT.
But, don’t let me or anyone else stop you from using nitrogen in your car if you wish, just know the benefits are small for the average driver.
But that doesn’t mean it a bad hose it just means it should be used on cars according to the DOT.
Sorry it should have read
But that doesn’t mean it a bad hose it just means it shouldn’t be used on cars according to the DOT.
I don’t know why you single out women, but most female drivers I know are religious about getting their oil changed every 3000 miles, and I haven’t run across any oil-change place that doesn’t top up your tires (with plain air) for free during the service.
So while getting tire pressure checked every 3 months may not be ideal, it’s not like they never get it checked.
Did your in depth car board discussions uncover any additional advantages N2 provides over hydrous air besides thermal conductivity, innerliner oxidization, rim corrosion, pressure variability over temperature, fire safety, less than 2/3 the leak down rate or nearly doubling the tire body life?
Or did you find any nitrogen disadvantages other than cost and availability (I get it for free half a block off my commute so it’s not a hard call for me)?
It’s not magic, of course they have to be filled correctly and regularly checked for pressure (they just get slightly better gas mileage between checks).
Your board missed an important point, however - the recommended ratio is not 100%, it’s 95% N2 (which equalizes oxygen partial pressure inside and out, minimizing oxygen migration and rubber degradation inside the tire body).
Fortunately, nitrogen has no such aircraft only limitations. It provides the same advantages in any natural/styrene-butadiene/polybutadiene rubber tire, from a 500lb rated wheelbarrow tire to a 140,000lb rated, 300psi space shuttle tire.
When the advantages are great enough that more and more major truck fleets are switching over (Wal-mart, after extensive in-house testing and cost analysis, being the latest), rest assured, you haven’t stopped me from using nitrogen.
I’m confused by a few things. Are you claiming that an about 80/20 mix of N2/O2 leaks 3 times quicker than a 95/5 mix? Also, what does a 1% difference in thermal conductivity between oxygen and nitrogen have to do with anything? Thirdly, do those gases deviate so far from the ideal gas law that a mixture containing lots of nitrogen and a little oxygen behaves significantly different from a mixture of lots of nitrogen and very little oxygen under constant volume and variable temperature? Finally, how does equalizing the partial pressure do anything to prevent oxygen from permeating the tire?
Your not the only one confused Mithras
As per Consumer Reports testing (http://news.consumerreports.org/cars/2007/10/tires-nitrogen-.html) N2 inflated tires lose pressure at 63% the rate of air (which would make air leak out about 1/3 faster).
Thermal conductivity (first on the ‘slight’ end of the ‘slight to moderate advantage’ list - I tried to be comprehensive since they don’t grade on a curve here) helps transfer tread and sidewall heat to the rim letting the tire run (slightly) cooler.
I’m not sure what you’re asking on #3, almost all the benefits of nitrogen come from it not having 21% oxygen and water vapor. If you can get it as cheap, dry argon would probably work just as well.
Here’s the math on balancing interior and exterior oxygen partial pressures (http://tirenitrogen.typepad.com/tirenitrogen/2011/08/what-is-the-correct-purity-for-nitrogen-tire-inflation.html), the sweet spot is actually 94.4% N2 to minimize oxygen atom migration through the tire body (with the subsequent internal rubber damage).
That business about equalizing the partial pressure of oxygen, as a way to keep the oxygen molecules from crossing through the tire, is just wrong. I can see that 94% could be the equilibrium state, but that doesn’t mean that oxygen molecules are permeating the rubber any more slowly, just that the net oxygen in equals the net oxygen out.
penumbrage is just bleating on about partial pressures as with every other justification (hazard of exploding tires, thermal conductivity of nitrogen, et cetera) in a vain attempt to buck up his increasingly untenable and unsupported stance that pure nitrogen is a better fill gas than dry air. For what it is worth, the permeability of gas (nitrogen or oxygen) through the monolytic body of the tire is negligable for automotive applications. It is possible for air to leak thorugh cracks in an intertube, but the construction of a radial or bias ply tire is such that that natural cracks (not punctures) straight thorugh the tread are not possible, and significant cracking through the sidewall (on a radial tire) will result in structural failure and catastropic collapse. Leakage from modern automotive radial tires not due to puncture comes from either an incomplete seal at the bead seat, incomplete seal at the valve stem joint, or leakage through a defective Schrader valve, not due to permeability through the tire body.
Personally, I run ultra-high performance all-season radials on my car (per manufacturer recommendation and preference), which are mounted by a reputable shop and checked every second or third fueling. Aside from puncture, I find that I almost never have to top off the tire pressure between oil changes (and rarely then); the few times I have noted leakage, it has inevitably been due to a puncture through the tread or a bad valve stem. I have literally run 20k miles without having to top off the tire pressure, using standard dry air, available at nearly any gas station. I have also never experienced this hazard of exploding tires about which penumbrage is so concerned, despite having been in one major accident (struck by a vehicle crossing right of way and pushed into the path of another vehicle) and having had three sidewall blowouts or tread separation (two due to road hazards, one due to an inadequate through-tread patch). I have never seen an automotive tire explode with sufficient amount of “combustable gases” to pose a personnel hazard to bystanders, much less occupants of the vehiclde, and as I don’t drive a heavy haul tractor down steep grades or NASCAR vehicles the difference in thermal conductivity of standard air versus pure nitrogen is entirely irrelevent.
Of course, there is no harm to filling tires with pure diatomic nitrogen, except to one’s pocketbook…but there is also no discernable advantage for automotive applications.
Stranger
Ah, I see. So instead of losing 3.5 psi (11.7%) in a year, a nitrogen filled tire will lose 2.2 psi (7.3%). To me, that’s a very slight advantage.
I’d imagine that a 1% thermal conductivity difference has so slight an impact on the rim it’d be nearly immeasurable.
I was referring to your claim that there is a
And I’m pretty sure that just isn’t true. You can calculate the change in pressure from temperature and completely ignore the type of gas.
I’m not questioning how you determine the partial pressure. I’m questioning why it’s relevant. Lets ignore the (highly relevant) point made above that tires are pretty impermeable. The oxygen molecules aren’t going to knock on the tire and ask how many are on the other side and only try to pass through if there aren’t enough. If we assume the tire is permeable, having the same partial pressure only implies that, on average, for every oxygen molecule that passes from the inside to the out one will do the reverse.
The slide that the blog you linked to references does not contradict this. The percent of oxygen in the tire increased because the partial pressures were different and so there were more to leak in than out. However, in total, fewer total oxygen molecules would have moved from one side of the tire to the other.
Vlad/Igor – I forgot to ask last post, did the welding video give you enough information from the pressure and temperature data to get a better idea of the quantities of pyrolitic gasses generated? Even with the 90psi starting pressure of the truck tire, there appears to be considerably more pressure, proportionally, than the 56psi you calculated for the 32psi automobile tire.
I realize the physics are very different from a car fire (with heat and combustible gasses constantly increasing, the internal combustion in the demo begins just as soon as a point on the rim reaches 460F, and it looks like that combustion builds heat, pressure and more gasses exponentially until the explosion) but I was hoping there was enough data during the linear, heat soak phase to make an estimate.
Mithras – True, there’s no order of magnitude gains, but with 250 million cars here even a 2 or 3% improvement represents a lot of pollutants we don’t have to put into the air and gas we don’t have to buy.
I asked earlier if the data on partial pressures was correct. I’m so used to errors being swiftly (and mercilessly) corrected here that I tend to assume that no objections = correct, but that’s why I come here, to sort the bogus from the bona fide.
But by whatever mechanism responsible, according to these sources N2 inflation slows tire body rubber degradation:
Effect of Nitrogen Purity on the Oxidation of Belt Coat Compound
Karmarkar & Herzlich / Akron Rubber Development Laboratory Inc and Herzlich Consulting Inc. 2006
Where they conclude the percentage of oxygen in the tire cavity is a significant factor influencing the rate of degradation of the tires and a tire filled with Nitrogen will degrade but at a significantly slower rate than tires filled with air.
Effects of Nitrogen Inflation on Tire Aging and Performance
Baldwin / Ford Motor Company 2004
Says oxidation and subsequent degradation of the steel belt rubber is significantly lower with nitrogen compared to air.
Nitrogen Inflation of Tires
Waddell / ExxonMobil Chemical 2006
Says durability of new tires increased quantitatively with decreasing % of Oxygen in the filling gas and shearography cracking of oven-aged tires was reduced using Nitrogen as fill gas.
Tyres Inflation With De-Oxygenated Air
Sabino / University of Bologna Mechanical Engineering Department 2000
Says a major disadvantage of using air for tire inflation is the deterioration of the tire casings lining
caused by oxygen.
The Science of Nitrogen Tire Inflation
Herzlich / Herzlich Consulting Inc 2006
Says nitrogen increases tire durability.
Why Inflating Tires With Nitrogen Makes Sense
Brodsky / Tire Tread Information Bureau 2005
Says nitrogen allows cooler running tires and less oxidation of tire components resulting in increased tire life, reduced tire aging, and a more durable casing.
Why Nitrogen Tire Inflation Extends Commercial Tire Tread Life
Mech / Drexan Corporation 2005
Which says two years of use with air can reduce tire casing strength by 60% compared to 20% for N2.
I don’t think it makes sense to pay an extra $200 or more for a set of premium quality tires (and the subsequent safety and peace of mind they provide) only to cheap out on a few dollars of N2 (presuming you’re unable to find it for free), fill them with air and slowly degrade them to the quality of cheap Chinese rubber before they wear out.
As I live in the Puget Sound area where the average humidity is over 70%, all my comparisons have been to hydrous air, the kind most gas stations and all home and pay compressors provide (water traps only remove droplets, virtually all the water vapor remains unless expensive desiccant or active air drying stages are added).
Assuming inflation air at 50% humidity (way low for me, perhaps high for you), how does that change the pressure over temperature curve and the thermal conductivity numbers?
Stranger On A Train – You said ‘explode’ in post #17 (and you can’t seem to get over it).
I showed you the FAA final report since you seemed ignorant of the fact that overheated natural/styrene/butadiene/polybutadiene rubber tires inflated with air generate explosive gasses and I further stipulated, clearly and repeatedly:
“… the hot rubber gasses combined with oxygen inside a burning tire can actually explode (given the higher pressures and containment of aircraft tires) to quash any possible argument from you that they wouldn’t make a car fire more severe.”
” If you burn them very, very fast (mixed with oxygen and heated to actual ignition like the higher initial pressure and stronger containment of an aircraft tire sometimes allows) you get an explosion that send pieces of rubber and rim through the plane.
If you just burn them fast (mixed with oxygen and released by a burning tire to an ignition source) you get an energetic combustion with a heat and pressure spike as they burn at the speed of ignition propagation through the explosive mixture.
If you burn them as slow as possible (mixed with N2 and released to an ignition source) they compete with the rest of the flammable vapors in the oxygen lean fire environment and only burn when the leading edge can find some, releasing their energy in the slowest, coolest, least energetic and safest manner possible.”
“I’m just talking about the difference between releasing a pressurized burst of explosive gasses when the tire fails (even without the containment and internal ignition required for an explosion) compared to merely releasing more flammable gasses into the combustible gas rich environment of a car fire – basically the same difference as using a lit match to pop a balloon filled with acetylene and air or popping one filled with acetylene and nitrogen - the same combustible gas energy is released much more rapidly and violently when pre-mixed with oxygen, generating more heat and pressure to intensify and accelerate your car fire.”
If you have any comments to make about things I actually said (as opposed to things you imagined I said) I would be glad to respond to them, just as I would have been glad to respond to any sources supporting your opinion, (had you been able to provide any other than an aircraft tire link irrelevant to the combustion dynamics of natural or synthetic rubber compounds in tires).
Meanwhile, as to your contentions from post #32 that “There is just no significant safety, longevity, or maintenance advantage over inflation with dry ambient air.“ and from post #58 that “…his increasingly untenable and unsupported stance that pure nitrogen is a better fill gas than dry air.”, I eagerly await (in spite of your switching my comparison from hydrous air to dry air) your rebuttal to the following sources, including the sources provided above for Mithras (his sources were selected for specifically addressing tire rubber deterioration from oxygen migration, but they ALL agree on the superiority of N2 over air).
Underinflated Tires in the United States
U.S. Government Accountability Office / U.S. Government 2000
Says tires inflated with nitrogen retain pressure levels longer and age more slowly.
Nitrogen Tire Inflation in a Long Haul Trucking Fleet
Konrad Mech / Drexan Corporation / Harris Transport 2007
(double blind, 110 million tire mile study)
“Moreover, fuel efficiency of the nitrogen inflated equipment increased by 3.3 percent.”
Initial Statement for Reasons for Proposed Rulemaking
Staff Report / California Environmental Protection Agency, Air Resources Board, (CARB) “
“Since pure nitrogen has a lower permeability than oxygen, the use of pure nitrogen would
improve tire inflation pressure retention.”
Tire Nitrogen Filling System – A Final Report to Industrial Technologies Sector of Ingersoll-Rand Corp.
Nader Jalili Ph.D; Prakash Venkataraman / Mechanical Engineering Dept. of Clemson University. 2008
Concludes that nitrogen inflation can maintain tire pressure at least 35% better than shop dry air.
Nitrogen Tire Filling – Field Data Analysis, NY City Transit – Flatbush Depot
Ashok Mathur / Air Products & Chemicals Inc. 2009
A 2.5% fuel savings and 20% improvement in tire life convinced NYCT to convert all remaining depots.
Million Mile Truck Tires Available Today - Oxygen & Moisture – The Killer of Tires
Lawrence Sperberg / Probe Forensic Testing Laboratory; El Paso, TX 1996
“The removal of most of the Oxygen (and the moisture in that Oxygen) results in significantly longer tire life.”