26

I saw this poster at a tire shop earlier today

Nitrogen advert

As the image quality isn't great, I'll reproduce the advert's claims in writing:

  • Take the lead! Ride smart!
  • [Nitrogen] for your SAFETY & ECONOMY
  • Nitrogen molecules are bigger than normal air
  • Less leakage
  • Fuel effecient [sic]
  • Less irregular wear
  • No presence of Oxygen
  • No oxidation
  • Longer tyre life
  • No deterioration
  • It's no wonder why aircraft and formula 1 cars Use nitrogen to inflate their tyres!

I would like to separate fact from fiction.

Which of the above-mentioned claims would translate to practical, tangible benefits for road-going passenger vehicles?

  • 1
    Great question +1 – DucatiKiller Sep 9 '16 at 21:17
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    As long as I do not get charged extra for it I will use it. I only get upset when a car dealer tacks on an extra fifty to one hundred dollars for it in my purchase. -Oh they have done a test here in our desert and show a reduction in tire temperature with nitrogen over plain air. – spicetraders Sep 9 '16 at 22:11
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    Just a little reminder: 1) Air is about 80% nitrogen gas, and 2) the tire is completely filled with air before they add their nitrogen gas. So, with pure air you get about 80% nitrogen into your tire. "Topping up" with nitrogen to, say, 2 bar above ambient means you get about ((80+100+100)/(1+2)) ~ 93% nitrogen into your tire. So instead of the natural 80% nitro you're now driving with 93% nitro. Can that make a difference? – JimmyB Sep 10 '16 at 20:33
  • 4
    @JimmyB That gives me an idea: Propane molecules are way bigger than nitrogen gas, and surely less leaks will increase safety! – Jason C Sep 10 '16 at 23:44
  • 1
    Yeah. But hydrogen is much lighter! Less weight = better fuel efficiency! :) – JimmyB Sep 12 '16 at 12:11
28

Summary
The difference for passenger cars is pretty small, but it seems to be quite real. The less you maintain your tires the bigger the effect is. In large fleets of vehicles, the effect can be quite large.

Get Nitrogen™
Further investigation of the site justinm410 linked to, getnitrogen.org, shows a number of studies that (assuming they're all legit) show some real difference between nitrogen-rich and regular air.

With passenger vehicles, the fuel savings were between 2 and 8% depending on the study and driver behavior. A driver who regularly maintains their tire pressure sees much lower benefits than one who just gets the pressures checked during oil changes (about twice as much fuel savings if you only occasionally check pressures). One could argue that just checking your tires more often would save as much as nitrogen-filled tires, but the reality is that most people don't, so a public campaign to use nitrogen for tires could potentially see significant savings across a population.

The biggest differences are seen on large fleets of heavy vehicles, where fuel savings were between 6 and 23%, and tire lifespan was increased anywhere between 40 and 86%. It seems that fleet vehicles aren't maintained as well as passenger vehicles, plus they have to survive most more strenuous conditions.

There are two main causes for the savings. First, nitrogen-filled tires leak more slowly, so your tires will be closer to their correct pressures at any given point. I.e., if your tires are normally at 32 psi, the regular air might leak to 30 psi in one month, while the nitrogen is still at 31.5 psi. Second, nitrogen-filled tires see less variance in pressure during use. This lowered variance is mostly attributable to the lowered moisture, so a device to dry normal air might see similar results.

There's also the issue of safety. A properly-filled tire will perform better, and with more predictability, than an improperly-filled tire. If the tire maintains a more consistent pressure, it follows that it will be somewhat safer, but there's no data on whether that difference is significant. Additionally, at least one of the linked studies cites "decreased number of blowouts" from nitrogen compared to regular air, but there's no information about how much of a decrease they saw.

I don't have any way to verify the studies, but they've got papers from Bridgestone, Firestone, the Drexan Corporation on behalf of the Canadian government, among others. Plus Jay Leno says nitrogen is cool, and he's a celebrity, so obviously you have to listen to him. I tend to take a site's source material with a dose of salt until outside references verify it. But at face value, it seems to indicate the sign in the OP is basically accurate.

Edmunds
Edmunds.com investigates these studies, and concludes that while the studies are basically accurate, it's probably more efficient to just buy better tire-measuring equipment and get on it more often. Still that doesn't really mean anything for people who know they don't ever check the tires. Edmunds themselves did a study showing even "car people" really aren't as good about this as they should be.

Many people, even at an automotive Web site like Edmunds.com, have never checked their tire pressure. This means the pressure is only adjusted when the tires are rotated, about once every six months to a year. This isn't often enough. Tires should be checked and adjusted at least once a month.

We also found that many drivers don't know what level to fill their tires to. Many people thought the pressure was listed on the sidewall of their tires. This is wrong. The correct tire pressure is listed on a placard found in the car's door, doorjamb, glove compartment or owner's manual.

Still more people seemed to be simply guessing how much air to put in their tires. They pumped air into their tires now and then to make sure they were over the required amount. But they didn't check and adjust the tires to make sure the tires were all approximately at the same level

The Tire Rack
The TireRack.com does their own study, where they conclude:

Overall, inflating tires with nitrogen won't hurt them and may provide some minimal benefits.

Is it worth it? If you go someplace that provides free nitrogen with new tires, why not? Additionally we've seen some service providers offering reasonable prices of about $5 per tire (including periodic adjustments for the life of the tire) to a less reasonable $10 per tire (with additional costs for subsequent pressure adjustments) or more as part of a service contract, which we believe exceeds the value of nitrogen's benefit.

Rather than pay extra for nitrogen, most drivers would be better off buying an accurate tire pressure gauge and checking and adjusting their tire pressures regularly.

Note that, again, their bottom line depends on drivers paying more attention to their cars. This is solid advice, but only helps if drivers follow suit. Otherwise, it seems nitrogen may be measurably better if it's cheap or free. Of note, both Get Nitrogen and Edmunds estimate about $100 a year could be saved with more consistent inflation. This means you'd still save some money, even with relatively more costly fill-ups.

Response for the specific claims made

  • Take the lead! Ride smart! Marketing hype, of course, but potentially accurate.
  • [Nitrogen] for your SAFETY & ECONOMY Presumably safety is true, but it's unknown how true (even Edmund's other study isn't helpful here); the studies show economy is true, to some degree.
  • Nitrogen molecules are bigger than normal air / Less leakage This paper explains that oxygen molecules have a slightly smaller "kinetic diameter", meaning they permeate through the rubber slightly faster than the nitrogen molecule. Since most of the non-nitrogen part of normal air is oxygen, this statement is true, if somewhat imprecise.
  • Fuel effecient [sic] The studies on the site show this is true, citing from 2 to 23% better fuel economy.
  • Less irregular wear It stands to reason less variance in tire pressures would lead to more even wear on the tire, but it's unknown if this is significant.
  • No presence of Oxygen / No oxidation These are somewhat hyperbolic, but true according to the site's cites.
  • Longer tyre life Shown by the studies to be true, citing 31 to 86% longer tire life, but these high numbers are for people who never check tire pressures and/or fleet vehicles.
  • No deterioration Again hyperbolic, but possibly true if the "decreased number of blowouts" is significant, and is caused by deterioration rather than low pressure.
  • It's no wonder why aircraft and formula 1 cars Use nitrogen to inflate their tyres! It's probably a bit silly to compare typical passenger cars to heavy duty equipment or purpose-built race cars, but the basic premise behind the use of nitrogen in these fields still holds in the field of passenger cars, albeit to a much lower extent.

Conclusion
The sign is accurate, but the real-world effect is mostly very small for passenger vehicles in normal usage. If you're lazy about maintaining your tires, the real-world effect of nitrogen becomes more practically significant, though still small. Safety is some concern, but a difference of 1 to 2 psi isn't likely to be the difference between no crash and seventeen fatalities.

  • 3
    Great answer. Impartial, detailed and backed up with data. – Zaid Sep 10 '16 at 9:16
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    I never understood the "use the placard for the tire pressure" advice . One can fit the same vehicle with different tires (size, compound), and I find it hard to believe that the proper pressure is the same for all. – Martin Argerami Sep 10 '16 at 10:22
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    At risk of an ad hominem, any scientific study offered to you by a website called "do something (TM)", while it might be a perfectly good study, has pretty well certainly been cherry-picked before posting to the site. The selection being in favour of studies that support the merit of doing that something ;-) – Steve Jessop Sep 11 '16 at 0:10
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    @MartinArgerami: You are correct that different tires, or even different vehicle usage, have a different ideal pressure. However, the correct pressure is a complicated subject, and will almost always be much closer to the manufacturer's recommendation than the sidewall pressure (which just indicates the maximum pressure you can safely use on that particular tire). So yeah, it's "wrong", but it's a lot less wrong in general than just filling it to max. – MichaelS Sep 12 '16 at 0:21
  • It should be mentioned that many cars these days have sensor based tire pressure monitoring system (TPMS). Thus, no need to check the tire pressure anymore; you will get a warning on the dashboard if tire pressure is low. – juhist Feb 15 '17 at 19:01
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Nitrogen molecules are bigger than normal air - Air isn't a molecule, it's a compound consisting of 78% Nitrogen, 20% Oxygen, 2% other. So that's a ridiculous comparison.

Less leakage - See above.

Fuel effecient [sic] - Two tires at the same pressure, one with air and one with nitrogen, will have the same fuel efficiency. See above.

Less irregular wear - This still hinges on the assumption that air leaks out of tires while nitrogen does not, which again, is ridiculous. Also see note about temperature variance below.

No presence of Oxygen - They're not selling pure Nitrogen, it's usually 95-98% pure.

No oxidation - Tires dry rot from the outside, so I don't see how this would help.

Longer tyre life - Not in any measurable way.

No deterioration - ?

It's no wonder why aircraft and formula 1 cars Use nitrogen to inflate their tyres! - Correct, it isn't a wonder. However, they generate far more heat in their tires than a passenger car.

Tire heat really is the difference when it comes to nitrogen vs air. A change in temperature affects air greater, especially since it contains some moisture. This is a relatively small difference and depends on moisture levels.

This really is snake oil for the average car owner.

See this link for more specifics:

  • Yup! Great answer. Nitrogen obeys all the gas laws like any other gas. – BillDOe Sep 9 '16 at 22:35
  • That spelling problem with efficient is in his translation, not the original. There was no reason to preserve it. And it is true--there's less effect from temperature. However, the effect is tiny--not worth bothering with. – Loren Pechtel Sep 10 '16 at 2:34
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    @BillOertell I was under the impression that the main advantage is the low water content, since water vapor (which condenses under low temperature and high pressure) in the regular tire air causes significant pressure variance. – Random832 Sep 10 '16 at 3:35
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    Nitrogen's "larger" than oxygen as far as permeability goes. From a technical perspective it's silly to say "air molecules" but from a marketing perspective it makes sense - marketing is about being palatable to the layman, not about being technically accurate. – Jason C Sep 10 '16 at 22:02
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    Correct. Nitrogen hype is weapons grade bullshit. Qualitatively the claims are correct, but quantitatively the difference is not realistically measurable. – Bohemian Sep 12 '16 at 1:51
14

Take the lead! Ride smart!

Marketing blahblah

[Nitrogen] for your SAFETY & ECONOMY

I am under the impression that air-filled tires also maintain their pressure, so I do not see a remarkable benefit

Nitrogen molecules are bigger than normal air

No: The bond length of N2 is 109,8 pm. The bond length of O2 is 121 pm. So nitrogen has a higher diffusion velocity than oxygen.

Less leakage

  • Same as above
  • Should(!) it be true that oxygen leaks more easily than nitrogen it would mean that the nitrogen concentration should be always increasing with every compressed air fill, since the oxygen leaks out. So you could have your nitrogen-filled-tire for free.

Fuel effecient [sic]

Same as above

Less irregular wear

Tires are subject to irregular wear when the suspension or brakes are defect or the pressure is not right. I do not understand how nitrogen is supposed to make a significant difference, assuming a regular pressure in the tire. See also above.

No presence of Oxygen

No: Since the tire is not getting mounted in vacuum there is still oxygen in the tire. Assuming a 2 bar pressure in the tire after filling with nitrogen there is still 33% atmospheric gas in the tire. This translates to 93% nitrogen.

No oxidation

Tires usually get consumed on the outside, not on the inside. Unless you flush your tires with nitrogen there should be still oxygen in the tire.

Longer tyre life

Same as above

No deterioration

Same as above.

It's no wonder why aircraft and formula 1 cars Use nitrogen to inflate their tyres!

One cannot compare the loads of formula 1 tires/aircraft tires with ordinary cars.

  • Aircraft
    • Aircraft tires can have special blowout valves that are supposed to cool the brakes or extinguish eventually fires. Ordinary air could impact that negatively. Cars do not have that kind of tires. Reference: FAA
    • Since compressed air contains always some moisture it could freeze at the extreme temperatures at flight level. Cars do not travel at 12000m height.
  • Formula 1
    • There loads on formula 1 tires and ordinary tires are not comparable.
  • they couldn't cycle it multiple times to get a lower percentage of air? – Random832 Sep 10 '16 at 3:37
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    @Random832 they could but I doubt they do – Martin Sep 10 '16 at 7:08
  • "So you could have your nitrogen-filled-tire for free." - Sure, but my tyres filter the air so dang sloooowly that it'd take decades to centuries riding the very same tire to reach 95% N2, so I'm happy the people at the shop spare me of that for just a few bucks ;-) – JimmyB Sep 10 '16 at 20:45
  • Of course, but since oxygen leaks out so slowly it should not be a big problem to use ordinary compressed air? – Martin Sep 10 '16 at 21:04
  • The (thermal) blowout plugs on aircraft tires are just to let the air out nicely instead of exploding if they get too hot. At that point cooling the brakes isn't anything to worry about, the ARFF guys will put those fires out shortly. – casey Sep 11 '16 at 0:21
4

There are some real benefits regarding using Nitrogen in your tires

The poster stated

Take the lead, ride smart

I don't know if it's smarter to use nitrogen

[Nitrogen] for your SAFETY & ECONOMY

Nitrogen molecules are larger than oxygen or hydrogen. As a result nitrogen filled tires tend to maintain their pressure for longer periods of time. It's more difficult for them to migrate through the rubber of the tire.

Nitrogen molecules are bigger than normal air

True

Less leakage

True, since the molecules are larger it's more difficult for them to get out of the tire.

Fuel effecient [sic]

I suppose this could be inferred as a possible truth if the tire is maintaining it's optimum pressure for longer periods of time and the end user does not validate pressures and add air as needed to the tire. This would be a claim that is based more on behavior than innate features of nitrogen.

Less irregular wear

False. I can find no reference that nitrogen would have less irregular wear than normal air. Again, this may be a behavioral claim if you have a tendency to not validate air pressures with regular air in your tires.

No presence of Oxygen

False, there will always be SOME oxygen in the tires, even if it's a tenth of a percentage point. A more accurate claim would be 'less oxygen'.

No oxidation

False, a more accurate claim would be 'considerably less oxidation'

Longer tyre life

False. Again, this is a behavioral claim based upon the maintenance of tire pressure using regular atmospheric air. It's certainly a possibility though.

No deterioration

False. As an imperative that there is no deterioration, there will always be some. Since the oxygen level is greatly reduces there will be considerably less oxidation of the internal rubber. As things currently stand, oxygen will deteriorate rubber but not at an alarming rate or a rate that we might consider dangerous to the internal tire rubber.

It's no wonder why aircraft and formula 1 cars Use nitrogen to inflate their tyres!

It's true. F1 cars and aircraft do use nitrogen in their tires.

  • 2
    I have never heard of somebody replacing a tyre becausd it was "oxidized" on the inside... Doesn't seem to be an issue for most. – JimmyB Sep 11 '16 at 13:35
1

Water in a tire gives more pressure when inside tire temp is higher. This is more an advantage because this higher pressure gives lesser deflection so lesser heatproduction. The tire inside gascompound ( air of Nitrogen or whatever) can get incidentially boiling point of water at 1013mb( 14.6psi)by the heat of brakes tranfered trough the rimms. Pressure advice is all to give the tire a deflection that dont give to high temp of the rubber at the speed its given for. But if by external cource, like severe braking or sunshine on tire, the tire inside is that 100degC/212degrF the rubber cant transport that much energy to the tire inside so gets hotter and gets hard and damages in next bendings.deflections. If enaugh liquid water to go over to gas in tire, the pressure will rise an extra 1bar/14,5psi by the water and this gives lesser heatproduction, and lesser chanche on damage to tires.

At normal cold temperature of tires, the extra pressure of water is only 0,025 b bar/1/3th of a psi.

Then about oxigen percentage. The law of Dalton states that every gas acts as if its the only gas , so the oxigen 21% in normal outside air, achts ( for diffusion for instance) as 21% of 1013 mb = about 0,21 bar/ say 3 psi. The tire inside air will work its way, so Partial pressure of oxigen is inside tire the same as outside . This leads to next. Tire with filled pressure 3 bar/44psi mesured overpressure, is in real pressure 4 bar /<>59 psi so Part pressure of oxigen then works its way to 0.21bar/3psi wich then is 0,21/4=5.25% . then inside and outside Pp of O2 is the same and the Oxigen will diffuse yust as quick into the tire as out of the tire. Roughly for 1 bar overpressure in tire O2 10%, 9 bar/2%.

Water also diffuses trough the rubber and probably quicker then oxigen, because not only the sise of the molecule is important but also chemical other factors, water is a dipole can be one of those factors. That is when water is gas, when its liquid probably it does not diffuse trought the rubber of tire at all. This can mean, that the ammount of liquid water in the tire can get different in time by complex situations like high humidity and temperature chanches at day and night. My suspections ( not proven) is that the amount gets more after a few years. But this does not influence the pressure more, because the amount of water-gas can is limited to that wich belongs to the temperature in tire. I found a spreadsheet about this Partial pressure of water in relation to temperature, and added the conversion from degr C to F, and from bar to psi.

As pigheaded Dutch self declared tirepressure-specialist, I kept myself busy with the nitrogen filling also, and found that oxigen diffuses trough the rubber about 3 times as fast as Nitrogen. Argon , a gas I thought would diffuse less because its a nobel gas, I was wrong, it diffuses about 2 times as fast as Nitrogen. But when filled , if possible, with 100% Nitrogen, the loss of Nitrogen in time, is a bit compensated by the oxigen that goes into the tire because the Pp outside is 0.21bar and inside zero bar. Stange but true the oxigen goes into the tire against the higher total pressure , because of that law of Dalton.

In the Formula1 world there is also an issue of pressure . There they fill with Nitrogen or dry air, to rule out the extra pressure rising by liquid water going over to gas.Temp in tire at races can get as high as 90degrC/190degrF Better would be to cool down the tires better, by active cooling of the rimm, so pressure stays lower too. I already supposed the idea of making the spokes in shape of ventilator blades , now they already have hollow spokes to get lower warrm pressure in tire. This would have more effect then dry air . if the tire inside is for instance only 45degrC instead of 90 degr C, the pressure will be substantially lower .

temp/Pp H2O/Pressure when filled at 65degr 21 psi if dry air so no infl of water 112degrF/1.4psi/24.2psi 190degrF/10psi/29.5psi

  • 1
    "by the heat of brakes tranfered trough the rimms" Excluding something like F1, no. "Water also diffuses trough the rubber and probably quicker then oxigen". Certainly not. "found that oxigen diffuses trough the rubber about 3 times as fast as Nitrogen" I see no way you could have scientifically tested this. This is heavy on academics and very light on real world application. – justinm410 Oct 5 '16 at 17:06
0

Tire degradation is due not only to oxygen itself [oxidation], radiation from direct sunlight contributes its own effects. You'll see lesser used trailers and motorhomes tarp or shield them from sunlight. On nitrogen, it's hinted at here and leakage is a factor dependent on the area [square inches] available and quantity of tires you maintain; ie trucking companies. Re; racing tires inflated w/ nitrogen maintain consistent pressure unaffected by temperature, preserving tread footprint chassis is adjusted for. It would help to evacuate 'air' before nitrogen inflation. Basically more inert than 'air'. Near useless for motorcycles, and automotive drag racing. F1, TransAm, CanAm etc, where they are turning right AND left sees most benefit. Lots of racing relies on milliseconds, so... Applies to opened wine too, oxygen is less friendly. And one more item of interest. Many tubular framed chassis marginalize thickness to save weight, big in decades past, huge with advent of CAD drawing, stress analysis and so on. Both have used Schrader fittings to pressurize the assembly and monitor for cracks with a installed gauge! A little observation tells you where to install, determined by whether an area is closed or a 'manifold.

0

A11four1 wrote " It would help to evacuate 'air' before nitrogen inflation."

In practice that cant be done to tires, but by filling with almost 100% Nitrogen from a cilinder, and then letting out air trough the valve to zero pressure , and reapeating this cycle a few times, you can come close to that.

Question is if this is needed?

JustinM410 makes comments to my former post. I seem to make that he writes that only in F1 the tires inside can get that hot as 100degrC/212F but when descending from the mountains and using the brakes to often, it can even happen to a normal car up to truck, an valve importer wrote me this in an answer to the maximum pressure of valves, so this is fact.

The 2times as fast diffusion of oxigen then Nitrogen and water as gas even faster then oxigen , is as acurate as I could find on the so reliable source internet, so can be different.

When I did administrative research on Nitrogen filling , I came to a way to determine this pretty accurate. This is filling the several empty tires of same specifications, so with absolute pressure of around 1 bar /14,5 psi, with diferent gasses from a cylinder, so more then 99% pure. For instance Nitrogen, oxigen, but also Argon, Helium. Fill them to the same pressure at the same temperature, next morning measure again so temp in tires in same room are the same as in the room, and write these down for every tire. Then measure pressure of every tire every month, and notate temperature in the room. Also one measurement after a year can be done, so less air escapes with every measurement. Then the pressure loss in time is only by the filled gas, because the 1 bar air empty tire has same compound and partial pressures as the outside air, so per saldo wont diffuse trough the tire . Found a way to calculate the diffusion speed ratio to Nitrogen , and by this the diffusion speed ratio can be determined pretty accurate. Not to 2 digits accurate but you then can see if Oxigen diffuses 2 or 2,5 times as fast as Nitrogen.

  • "an valve importer wrote me this in an answer...so this is fact" It is not. If you're braking down a mountain, how could you possibly differentiate heat from rubber friction with road vs. conducted heat from the rim? "several empty tires of same specifications" Exactly, that's not scientific. They are all on different tires and different rims. Had you all filled them up with the same gas, you'd have gotten different measurements after a year. – justinm410 Oct 7 '16 at 19:30

protected by Pᴀᴜʟsᴛᴇʀ2 Oct 5 '16 at 19:06

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