Nitrogen in the tires
March 10, 2010 12:43 PM   Subscribe

Would initially filling my automobile tires with pure nitrogen then later topping them off with air cause any long or short term problems with the tires? Does the pure nitrogen have any real effect on tire life or performance?

I buy my tires at Costco who make a big deal about the fact that they fill your tires with nitrogen, putting green caps on the valve stems to indicate this.

The problem is that when I have my oil changed, the mechanics refuse to top off my tires (with air, I assume) unless I insist. When I got new tires last night, I asked for black valve stem caps so that I no longer have to do this. The Costco tire guy agreed to do this but ominously told me to make sure to never put anything but nitrogen into the tires.

My questions are:
1. Does nitrogen make any difference in the first place?
2. Does topping the tires off with air make any difference?

My thought is that atmosphere is already 80% nitrogen so the 100% nitrogen thing is just quackery anyway. I love me some Costco, but the insistence on pure nitrogen just seems silly.
posted by dforemsky to Science & Nature (21 answers total)
 
No, nitrogen makes no real difference in the first place, no you won't hurt anything (afaik). Snake Oil.
posted by Cosine at 12:44 PM on March 10, 2010


I remember a pretty good Straight Dope column on nitrogen tires.
posted by krilli at 12:46 PM on March 10, 2010


Nitrogen can reduce corrosion on your tires and/or rims. This may or may not reduce tire pressure loss over time.

It's also a way to charge more by offering a premium service.
posted by blue_beetle at 1:01 PM on March 10, 2010


Mr. F's straight-out-of-a-Scorsese-movie mechanic sighed and said "Why'd you let him do that?" when the dude at the tire shop put straight nitrogen into our car's tires. Anecdotal, I know, but Steve's always had a sharp eye for a con.
posted by fairytale of los angeles at 1:15 PM on March 10, 2010 [1 favorite]


It's probably not worth it.
posted by Dasein at 1:16 PM on March 10, 2010


Does nitrogen have a lower coefficient of volume expansion? That is, does it change the gauge pressure on your tires less than regular air when you go from summer to winter?
posted by Wild_Eep at 1:16 PM on March 10, 2010


Air, the 'regular' stuff is already 78% nitrogen. Less than a quarter is not... whatever it is that is supposedly detrimental.

I would be interested in knowing if over, say, ten years there were any appreciable difference the corrosion of wheel rims or tires filled each with 'pure' nitrogen and regular 'air.'
posted by From Bklyn at 1:32 PM on March 10, 2010


to answer the important part of your question-no it doesn't hurt to put in regular air into tires filled with 100% nitrogen. Air is moslty nitrogen (78% as Bklyn stated). The rest is mostly oxygen which is pretty close to nitrogen in weight and thermal properties. Nitrogen does expand a little less when warm and has a higher specefic heat (means it takes more energy to heat it up) but the difference is minor. The big advantage is the pure nitrogen is drier (no water vapor) which has properties not too good for tires. Mostly that it goes through its triple point under conditions found in tires (can be solid/liquid/gas depending on conditions all found normally in tires throughout the year). However the amoutn of vapor in tires fill with air is so small as to be meaningless for the average car even if driven by an expert.

The only big things changes for tires that effect handling are check air pressure for seasonal changes (as avg daily temps change pressure can change for the tire) and big elevation changes (like sea level to 8000+ in a single drive). In reality just check the pressure every oil change, fill with whatever you have available (hell even co2 works ok) to the manufacturer recommend pressure for the car and don't worry about it. Sure as hell don't pay extra for nitrogen though-its not harmful but it doesn't do you any good either.
posted by bartonlong at 1:52 PM on March 10, 2010


Seconding bartonlong. The only problem with regular compressed air is if the shop has a poor quality drier and a lot of volume the air could have excessive water in it which will cause more variability in pressure over temperature. Even then it's probably not enough to worry about. Race teams started using Nitrogen mostly when some tracks prohibited air compressors in pit areas and it's kind of trickled down to consumers as an upsell from there.

PS: I don't think I've ever seen a wheel rust from the inside out, not even multi piece tubeless rims or split rims.
posted by Mitheral at 3:57 PM on March 10, 2010


Right. If you pay more than a dollar or two for the nitrogen, it's probably not worth it. Because given the numbers involved, that's the extent of what 78% nitrogen versus 99% nitrogen could possibly save you.

But don't discount that 20something% oxygen, I mean, that's enough to cause rust all over the rest of the car, why not rust (or that white aluminum oxidation) inside the wheel? Especially if you've accidentally chugged a bunch of moisture in there.

On the other hand, if you are chucking quarters into air hoses at any reasonable pace throughout the ownership of the tire, and the nitrogen is better at maintaining correct pressure, it *could* be worth it.
posted by gjc at 5:18 PM on March 10, 2010


If you were driving a race car, you might derive some benefit from the smaller expansion-from-heat nature of pure nitrogen. However, you are not a race car driver, and there's absolutely no reason for you to care one way or the other about whether it is normal everyday atmospheric air or pure tanked nitrogen in your tires. Mix 'em at will, don't spend the extra money for pure nitrogen, etc. etc. etc.
posted by davejay at 6:11 PM on March 10, 2010


The only big things changes for tires that effect handling are check air pressure

This. Not just for seasonal changes, though, check them anyway.

The rest is horse-puckey. Road cars do not in any way need Nitrogen in the tyres - the issue is moisture and the only reason a lot of race teams use it in their tyres is for more stable and predictable pressure rises when the tyre warms up - basically - it's a lot easier to set your cold tyre pressures for a particular desired hot tyre pressure (and hence known tyre stiffness) when on the track.

However, back to back tests with dry-air (compressed then dried as part of a decently expensive compressor set up) show that the only real issue is the moisture anyway - the temp curves matched very closely indeed from Nitrogen to Dry air. Being as a road car doesn't see anything like the temperature changes that we do on race cars means this is a non-issue. As for corrosion and tyre damage, the corrosion won't be much of an issue and tyre degradation from sunlight will bugger your tyres far faster and more seriously than normal compressed air in them will.

It is, as mentioned, snake oil. Any half decent garage will have some sort of air drier on their system to protect their own air tools and equipment (although not necessarily the ones available on forecourts at petrol stations). However, the issues arising from incorrect tyre pressure unquestionably and massively outweigh any problems from a bit of water vapour in your tyres.

Check your tyre pressures regularly, and laugh in the face of the money grabbing idiots that are trying to sell you Nitrogen for your tyres.

Race teams started using Nitrogen mostly when some tracks prohibited air compressors in pit areas

No, it was the stability of tyre pressure through heat play-off that started Nitrogen (and all sorts of rare gases) being used in tyres. There is no pit lane ban on compressors in international motorsport.
posted by Brockles at 8:01 PM on March 10, 2010


I have a 2000 Honda accord, with alloy wheels. After one oil change (and tire top-up), all four tires completely deflated overnight. When I had it flat-bedded to Costco the next day for new tires, I was informed that all four rims were 'corroded' inside (aluminum oxidation).

I assume the Jiffy Lube I had gone to the previous day had a bad dryer. I've since stuck with the n2 I got at Costco; if you bought the tires there, they will top them off for free. They've never asked to see a receipt.
posted by pointless_incessant_barking at 7:38 AM on March 11, 2010


After one oil change (and tire top-up), all four tires completely deflated overnight.

There is absolutely no way at all, in any possible way in fact, that these two things are even in the slightest bit related. Zero. Not at all. Corrosion is not an instant button and take a very, very long time to have an effect. In addition, the chances of 4 wheels corroding at exactly the same rate is remote to the point of impossibility.

It sounds to me like someone let your tyres down. Maybe you upset someone. This is, without doubt (and includes mistaken identity and 'kids') overwhelmingly the most likely explanation.

Corrosion causes slow punctures by bleeding air from an imperfect seal around the tyre. A tyre that deflates over night is not exactly a 'slow' puncture. Your rims may well have been corroded, but they certainly did not do so in anything like a period less than several years.

You have, I'm afraid, been totally suckered into the black magic surrounding Nitrogen in tyres.
posted by Brockles at 8:17 AM on March 11, 2010


You have, I'm afraid, been totally suckered into the black magic surrounding Nitrogen in tyres.

Except that Costco fills them for free... Brockles I think you're right on every point and I agree that filling your tires with nitrogen is not worth going out of your way for it, but as long as Costco re-fills the tires for free and it's easy - whatthehell (that is, as long as you realize it's snake oil and there is no difference what so ever).
posted by From Bklyn at 12:01 PM on March 11, 2010


Except that Costco fills them for free

But the marketing still worked so the hook has struck, even if the cost isn't immediate; the customer will return to Costco every time they want their tyres filled. So I guess they'll do some shopping there while they wait. And probably buy their next tyres from there because, you know, they NEED the nitrogen that Costco provide for them...

It doesn't need to make profit if it creates return business. All from a made-up pseudo-scientific 'advantage' from using Nitrogen. That kind of thing is, to my mind taking advantage of people and I find that irritating. There are zero tangible benefits from using Nitrogen in a road car's tyres, only theoretical ones that are negated by the many other elements having a far greater effect on the aspects Nitrogen is supposedly 'fixing'.
posted by Brockles at 5:57 PM on March 11, 2010


After one oil change (and tire top-up), all four tires completely deflated overnight.

There is absolutely no way at all, in any possible way in fact, that these two things are even in the slightest bit related. Zero. Not at all. Corrosion is not an instant button and take a very, very long time to have an effect. In addition, the chances of 4 wheels corroding at exactly the same rate is remote to the point of impossibility.

I disagree with you, Brockles; there's corrosion and then there's corrosion.

If the the quick lube blew rusty water into pointless_incessant_barking's aluminum wheels, a thing I've seen out of service station compressors on several occasions, corrosion could have proceeded quite rapidly.

2Al + Fe2O3 ==> Al2O3 + 2Fe is the basis of thermite, after all, and is so energetically favored it doesn't necessarily require a magnesium ribbon to be pretty fast.
posted by jamjam at 12:46 AM on March 12, 2010


Wouldn't she/he then have legal cause to sue them for destroying her wheels?

(And obviously what we are saying is that it was not the mixing of "Pure Nitrogen" and "Regular Air" that caused the corrosion, but the faulty maintenance of a standard air compressor). (So if you want to argue that buying air from a 'known' source is more... No, this is silliness. I've been driving cars and motorcycles for about thirty years and I've never had any trouble, nor do I know of anyone who has ever had any trouble, nor have I ever heard of anyone who has ever had any trouble, with tires or wheels resulting from bad air out of a gas station's pump. I will stick to this entirely unscientific assessment of the harmlessness of 'regular air', sleep soundly and, I am sure, never feel pangs of anxiety that I have filled my tires with the 'wrong air'.)
posted by From Bklyn at 2:17 AM on March 12, 2010


jamjam writes "2Al + Fe2O3 ==> Al2O3 + 2Fe is the basis of thermite, after all, and is so energetically favored it doesn't necessarily require a magnesium ribbon to be pretty fast."

However their isn't any raw aluminum inside a wheel rim. At a minimum it's been painted and even places where it may have been scratched will essentially instantly form an oxidized coating. Thermite works because of the huge surface area of the two metals created by grinding them to a fine powder. It isn't relevant to a discussion about wheel corrosion anymore than a warning to cooks about the possibility of the sack of flour in their kitchens being an explosion hazard.

I'm in agreement with Brockles. there is no way, no how that the quick lube place adding air to adjust tire pressures (which they shouldn't be doing anyways, the tires not being cold) could have caused pointless_incessant_barking's deflation event. Even if water in air could cause wheel corrosion, which I doubt having never seen it, even the proponents of that theory (in classic snake oil form) don't claim such quick and consistent results. If they did it would be easy to test (and alloy wheels would be going flat all the time). Brockles' theory of either prankster kids or a disgruntled neighbour letting your tires down makes the most sense. Though if pointless_incessant_barking's tires were very hot and the quick lube place released a bunch of air from the tires and his car features beadless rims (unlikely) then when pointless_incessant_barking parked and the tires cooled the resultant loss of air pressure could have let the tires break loose from the rim and deflate.
posted by Mitheral at 7:22 AM on March 12, 2010


I did look around today for some support for my claim that rust can enhance aluminum corrosion and found essentially nothing.
posted by jamjam at 12:03 PM on March 12, 2010


However their isn't any raw aluminum inside a wheel rim. At a minimum it's been painted and even places where it may have been scratched will essentially instantly form an oxidized coating.

Not to mention that it is aluminium alloy, not pure aluminium anyway.

there's corrosion and then there's corrosion.

This makes no sense at all. Yes, some circumstances can increase the rate of corrosion, but it would make a time difference of several years down to (at most) several months. No way in hell is there anything other than some sort of strong acid (alkali/other strong chemical other than air) that you could pump into a tyre that would deflate all 4 of your tyres within 12 hours.

I did look around today for some support for my claim that rust can enhance aluminum corrosion and found essentially nothing.

Would researching that (or in fact anything) first perhaps be a better plan before making statements that suggest putting air with trace rusty water into your tyres is akin to making a thermite reaction?
posted by Brockles at 2:49 AM on March 13, 2010


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