Do you use Nitrogen in your tires?

[dennis thompson]

I was at the car dealer and picked a notice about nitrogen in your tires, it says:
increase tire life by up to 30%
improve fuel economy
reduce chance of tire failure up to 50%
improve braking and handling

it goes on with many other benefits
what do you think, is this correct?
do you use nitrogen in your tire?
thanks

[Stephen Cherry]

I usually just buy tires from tire rack and mount them myself, using air- which is mostly nitrogen.

Nitrogen leaks a little less than oxygen, but, from what I have read, good tires have extra rubber of a certain type that keeps the air in. Cheap tires skimp out on this. The big thing to avoid is the water in the tires- if this is condensing and evaporating with temperature, it will cause larger changes in pressure.

In any case, I just use air, and my tires last OK.

[Jason Roehl]

Nitrogen is used in airliner tires and racing tires. For a typical civilian vehicle, nitrogen has one, and only one, purpose: to separate the civilian from more of their dollars.

[Dave Richards]

As Stephen alluded, what is in your tires now is already 78% nitrogen. I expect you'd be just as well off to find someone who has a dryer on their compressor so you don't get water in your tires when you fill them.

[Eric DeSilva]

Just out of curiosity, anyone know why they don't use CO2? I used to use CO2 cylinders to fill flats on my bike--as a gas, it is nice and compressible. I've also seen some off-road fix-a-flat kind of cans that seemed like pure CO2. Too expensive?

[Curt Harms]

Nitrogen is used in airliner tires and racing tires. For a typical civilian vehicle, nitrogen has one, and only one, purpose: to separate the civilian from more of their dollars.

At least for aviation use, the absence of moisture is the reason for nitrogen, or so I was told. I wonder if it'd also be less corrosive without the 21% oxygen.

[Jason Roehl]

At least for aviation use, the absence of moisture is the reason for nitrogen, or so I was told. I wonder if it'd also be less corrosive without the 21% oxygen.

I believe it's also for the fire-reduction benefits--those tires get very hot, and if there's a fire, then there's not compressed air containing oxygen to contribute. If a nitrogen-filled tire blows on landing due to a fire, it just might put the fire out by starving it of oxygen briefly (kind of like oil well fires are put out with dynamite).

[dennis thompson]

At least for aviation use, the absence of moisture is the reason for nitrogen, or so I was told. I wonder if it'd also be less corrosive without the 21% oxygen.
One of the suggested benefits I didn't mention in my original post was " reduce wheel corrosion", although I have been driving for many years and have never had a problem with wheel corrosion

[mike holden]

I was at the car dealer and picked a notice about nitrogen in your tires, it says:
increase tire life by up to 30%
improve fuel economy
reduce chance of tire failure up to 50%
improve braking and handling

it goes on with many other benefits
what do you think, is this correct?
do you use nitrogen in your tire?
thanks

The answer to this is in the third line: "improve fuel economy". If it did, then the car manufacturers would be specifying nitrogen as the proper inflation gas. They are searching for the slightest increase in fuel economy to meet federal mandates.
They do not specify nitrogen, so at least one of those claims is debunked.

The place where I buy tires, fills them with nitrogen, places a little green ring on the filler cap to remind me. I just top up the tires from my own compressor (air) or if on the road, the local gas station (air).

I would not go out of my way at all for nitrogen.

Mike (M.Sc. in Chemistry; retired from Chrysler)

[Steve Schlumpf]

Dennis, my wife has nitrogen in the tires on her SUV and I have air in the ones on my truck. The nitrogen have held their pressure for over 3 years (35,000 miles) and I have to check and refill my truck tires every couple of weeks! I notice a difference in handling because of the tires... the nitrogen are firmer and do not seem to be subject to weather changes. My truck tires get flat spots from sitting in the garage overnight - especially in the wintertime - her's do not. Next time I get tires... I will get the nitrogen.

[Dan Hintz]

One of the suggested benefits I didn't mention in my original post was " reduce wheel corrosion", although I have been driving for many years and have never had a problem with wheel corrosion

This is the biggest thing (using your brain, not the corrosion thing). For all of the benefits they claim for Nitrogen and all of the horrors they claim for shop air, all one has ot do is look to the past. How many wheels have you ever heard of that corroded because they used shop air? Zero. How do you increase tire life by 30% when the damage to a tire is the reduction in tread thickness due to road wear? You can't. How can you claim to reduce tire failure by 50% when you don't specify what the failure mode you're reducing is? You can't. Not to mention if you could improve failure rates by such a high degree, the NTSB would all but demand it be used.

When I go to the oil change shops, they give me all kinds of useless figures for how each changed component will improve my gas mileage. One day they were going all out, so I added up the percentages in my head... they were essentially promising to improve my gas mileage by 50-60% more than a car right off of the assembly line. Obviously impossible, but they didn't stop to think before speaking.

[Jason Roehl]

One more on the nitrogen thing.

Let's say you fill your tires to 40 psi (I know, high for cars, low for trucks, but the number is a little easier for the following math) with shop air (remember: 78% nitrogen, 21% oxygen, 1% other stuff)

Over the course of a few weeks, your tire drops to 32 psi--because it lost all the oxygen, but not the nitrogen (just using the pro-nitro sales folks logic here). So you top it off with shop air again to 40 psi. Now the pressure over a few weeks drops due to losing oxygen (but not nitrogen!), but to what? well, 32psi is ~80% of 40 psi, then we added 8 psi of 80% nitrogen, so now the nitrogen is about 38.4 psi of the 40 psi. One more cycle and you're up to 39.7 psi due to nitrogen, very little oxygen, and would read 40psi on most gauges commonly available.

Okay, I also have one more: what procedure do these tire shops use to fill tires with nitrogen? Do they simply hook up the nitrogen tank and push in the nitrogen? Because there's still ambient air inside the tire from when it was mounted. They certainly can't pull a vacuum first, as that would collapse the tire, breaking the bead's seal. Do they then deflate the tire and re-fill with nitrogen several times?

Either way, it's snake oil.

Steve, I suspect you just need to have your truck tires re-mounted and bead sealant used. It doesn't take much contamination for a bead to allow a very small leak. I've had truck tires that went years without needing air. As for whether tires get me 30,000 (partial life due to uneven wear) or 40,000 miles (full life due to consistent tire pressure), I don't really care--once the tires are in their last 1/4 of tread life, they're just about worthless in water, snow or mud anyway.

[David Weaver]

Do they charge to put nitrogen in the tires, or are they looking to sell nitrogen as a benefit of getting your tires done there?

I've never had nitrogen in a tire, and I've never had tires that needed air more than once every 6 months unless they've had a nail/wire/screw hidden in them somewhere. Never seen wheel corrosion issues, either. I keep my tires at 40 psi cold.

If the tires are at the same pressure with air and nitrogen, I find the fuel economy claims *very* suspect, and it gets a little irritating to see everyone trying to sell fuel economy with every device, elixir or service that goes on with a vehicle. Those of us who keep after our cars aren't going to find better fuel economy without getting a different car. Those who don't...should learn to keep an eye on the basic things in their cars.

[Matt Meiser]

I noticed Costco, and I think Belle Tire which is one of the major regional players around here use nitrogen at no charge. I've heard some of the others advertising it. Costco appears to have a machine that "makes" nitorogen" which would I suppose would be the exact opposite of a medical oxygen concentrator. Remove the 20% oxygen from the air and you are left with mostly nitrogen.

[Steve Schlumpf]

Jason, my truck is a 97 Chev S-10 and the reason - or so I have been told - that the valve stems leak is because of using aluminum wheels. I replace the stems every couple of years and things work great... until they don't and the process starts all over again.

The dealership we go to does not charge for nitrogen. Course, that could be to get everyone to try it, then charge for the service at some point in the future.

[Jerome Stanek]

Dennis, my wife has nitrogen in the tires on her SUV and I have air in the ones on my truck. The nitrogen have held their pressure for over 3 years (35,000 miles) and I have to check and refill my truck tires every couple of weeks! I notice a difference in handling because of the tires... the nitrogen are firmer and do not seem to be subject to weather changes. My truck tires get flat spots from sitting in the garage overnight - especially in the wintertime - her's do not. Next time I get tires... I will get the nitrogen.

If your tires leak now they may still leak with the nitrogen I had air in my truck and didn't have to add for over 5 years Nitrogen in the suv and had to add about once a year.

[Steve Schlumpf]

Jerome - you are probably right about that! I was thinking more about when I get a newer vehicle... then switching over to nitrogen. Just my personal experience... which could be because of the tires used, wheel material or something else... but the nitrogen has been a lot less hassle for me to deal with.

[Stephen Cherry]

It's true- in the old days, some steel wheels would rust on the inside due to bad paint and water in the air. This is something that I saw back in the 80's with older wheels. I don't think corrosion is a problem with modern wheels though.

As for some tires leaking and others not- some tires have an extra layer of butyl rubber to keep them from leaking, and other cheaper tars do not.

[Robert Delhommer Sr]

Another way to make money. 78% is good enough for me. :)

[Steve Peterson]

I agree that the claim of 30% better fuel economy is mostly snake oil. Sure you will get better fuel economy with properly inflated tires and 100% nitrogen may leak out slightly slower than 78% nitrogen. If you let 22% of the air out of your tires and drove around like that, then you will get poor fuel economy. All you need to do is re-inflate the tires and you are back to the original state. As long as you maintain proper pressure, you will get the same fuel economy with nitrogen or air. I believe all new cars are required to monitor tire pressure, so there is no difference.

Steve

[Mike Henderson]

It's just marketing. I agree that the most important thing is to keep moisture out of the gas that's put into the tire, whether it's nitrogen or regular air.

Mike

[Dan Hintz]

I noticed Costco, and I think Belle Tire which is one of the major regional players around here use nitrogen at no charge.

Funny you should mention Costco... SWMBO and I signed up there just a couple of months ago because (among other things) they carried the same tires she already had on the car (she blew through a sidewall hitting a curb, and I didn't want to mix/match tires). I didn't know it at the time, but they use Nitrogen exclusively to fill the tires. Last week she was getting her oil changed at the local shop and, per their usual process, they were going to fill up the tires (one was getting low... I know, a tire filled with Nitrogen, getting low... shocker!). They didn't want to do it because they didn't use Nitrogen, and they didn't want to "contaminate" what was in there. She called me, I called "BS", then I told them to swap out the green stem caps for the regular black and "contaminate" away. They didn't swap the caps, but at least the topped off the tires.

Really? You don't want to "contaminate" the Nitrogen with shop air? <sigh>

[David Cefai]

Nitrogen inflation is not available in my country. I am a chemist with 38 years industrial experience. So a lot of what follows is not based on a nitrogen experience.

The nitrogen molecule is a little smaller than oxygen. Consequently it will diffuse out of a tyre faster if that were possible, On the other hand the difference is minimal.

Air contains ~20% oxygen. This oxidises stuff. There is enough oxygen in air to maintain a fire.

Oxygen inside a tyre will oxidise the rubber. Oxygen outside the tyre will also oxidise the tyre! So will sunlight. Exhausr fumes don't do the rubber any good either.

The tendency today is for a tyre to suffer structural failure, from the outside, before the tread wears down to an unsafe level. At least that's what happens in Malta. (Max temp is >100 deg F in summer. Min temp is 36 deg C on a REALLY cold day).

So pumping with nitrogen is essentially a waste of time. To cover some of the other possibilites mentioned in this thread, at the pressures we are considering there is no difference in "compresssibility". Carbon Dioxide would diffuse out of a tyre more slowly than air but why bother?

The water issue could be a major factor in corrosion. The presence of some CO2 in the tyre could make things worse - it could make the water a little more acidic.

I hope this helps.

[Lee Schierer]

Most dealers around here have dropped the nitrogen tire filling scam and just use air. As noted, there is oxygen in the air in the tire before it is pressurized and it is never removed.

The biggest culprit to wheel corrosion and air leakage on tires is clip on wheel weights on aluminum wheels, even the coated clip ones. In the past 10 years, aluminum wheels have become very common on vehicles in order to decrease weight and increase fuel economy. When the wheels are manufactured, they are anodized to protect against corrosion. When they pound on the clip on wheel weights when the tires are balanced, the clips cut through the anodize and leave exposed aluminum in contact with steel. Add a little moisture and some salt and you have a miniature galvanic cell eating your wheel. In northern states where salt is used on the highways in the winters this corrosive action can produce bubbling in the aluminum that eventually will raise the rubber bead enough for air to leak out. Aluminum wheels will leak about a pound per week or more meaning that most people who aren't religious about checking tire pressures are driving on under inflated tires.

Although all new cars come with clip on weights, on all my cars, when I purchase new tires, I insist on stick on wheel weights to stop any additional corrosion. So far it has been a pain to insist, but on my oldest vehicle (2004), The wheels still look brand new where the beads seat and the tires hold pressure for months, which is fine since my service shop checks the air pressure during the oil changes.

[ray hampton]

If your tires get moisture in the tires and it condense to water , DO the water freeze during the cold weather when the car are park overnight ? will the ice cause a unbalance condition ? how long will this ice take to melt at zero temperature ?

[John Stankus]

Another chemist here. Nitrogen should effuse (leak) faster than oxygen by the square root of 8/7. (7% faster) Racing applications of nitrogen is to make sure there is no moisture. Liquid water in the tire will contribute to pressure build when the tire gets hot. ( or greater pressure drop when it gets cold enough to condense out the water)
Carbon dioxide would work fine. I know some auto crossers who have a CO2 tank that they run an impact wrench off of to change tires and to fill the tires to pressure

John

[Dan Hintz]

If your tires get moisture in the tires and it condense to water , DO the water freeze during the cold weather when the car are park overnight ? will the ice cause a unbalance condition ? how long will this ice take to melt at zero temperature ?

Worst case would be a couple drops of water... if that unbalances your entire wheel you have bigger issues to deal with.

[Phil Thien]

Wait...

I thought oxygen was heavier but SMALLER than nitrogen. Nitrogen should leak more slowly.

But now two chemists are saying oxygen is larger? David Cefai and John Stankus are saying it would leak faster?

Which one is it?

[ray hampton]

Worst case would be a couple drops of water... if that unbalances your entire wheel you have bigger issues to deal with.

couple drops of water, I see tires with a cup or two of water and I am talking big cups

[Dan Hintz]

couple drops of water, I see tires with a cup or two of water and I am talking big cups

Do you understand how much water vapor is required to condense to two cups of water? Now try to get that same amount of vapor into an area the size of a tire. Good luck.

[Brian Elfert]

Tires with cups of moisture must have been filled in a high humidity environment with no moisture eliminator on the compressor. This reminds me that the compressor I fill my tires with doesn't have a moisture eliminator right now as the bowl cracked and I had to take it off. I have another NOS one, but a bit worried about it cracking too.

[Pat Barry]

Its really not a question of leaking air out. The thing is compressed ait can be full of water. Here in MN if you wake in the morning and its below zero your tires will be looking a bit low on pressure due to the water vapor in the tire freezing. So your tires will be soft and consequently you wlll have poor gas mileage, for a while. Once the tire heats up, lets say from driving on the freeway, the tire pressure will come back up. So, driving on soft tires will result in lower gas mileage, but for how long? Now if a tire gets too soft the bead can leak and it will really be a problem of course. Nitrogen, if its pure dry nitrogen will not suffer from the same condensation driven tire pressure reduction so you will get better gas mileage. Water in steel wheels can cause corrosion. Do I buy it though? NO. I've lived and driven here all my life and I can't see paying for nitrogen. Interesting though, I think NASCAR uses nitrogen specifically to minimize the fact that the tire pressure will go thru the roof on a tire when driven at 200 mph, heavy braking, tire scrubbing, etc. They need the better consistency in air pressure that they get from nitrogen.

[Chris Parks]

I haven't read all the thread but let me say that I use nitrogen in our superkart tyres. There are a couple of valid reasons but they are all tied back to the fact that it is a dry gas with very low water content when supplied in a bottle and not generated locally at the tyre company. Having said that if I had the means to dry compressed air to the same level and compress it to the same level we would use normal air less the moisture. It is the moisture content that gives us problems, as the tyres get hotter the moisture component expands and we lose our ideal tyre pressures thus affecting the handling of the kart. Those that don't use nitrogen have to learn to compensate for this pressure rise but less for cars I would think. Any inert gas that does not contain moisture will give the same results, it does not have to be nitrogen. The reason it is pushed is that some clever person(s) have made machines and are selling or leasing them to workshops and they produce Nitrogen locally and do not have to buy in bottled gas. How good the nitrogen is moisture and purity wise is open to conjecture I would say.

[David Weaver]

I'm figuring the part you mentioned is right, that someone went around and marketed machines to places who do tire services, they got taken on them, and now they feel the need to either charge or boast about nitrogen to try to get the money back out of the machines.

[David C. Roseman]

FWIW, Costco routinely uses nitrogen to fill all the new tires, all brands, that they sell and install, nationwide. As savvy as Costco's management is, I doubt they were sold a bill of goods on the machines. ;)

David

[Art Mann]

Do you understand how much water vapor is required to condense to two cups of water? Now try to get that same amount of vapor into an area the size of a tire. Good luck.

Yes I do. The claim you quoted has got to be one of the wildest claims i have ever seen on the internet.

[Larry Edgerton]

We use Nitrogen in race tires because it is less affected by heat. No other reason, other than air pressure remains more consistent.


Now if you have 900 hp and do a lot of tire spinning at high speeds you may want to run nitrogen. We have the setup in the shop and just run plain old air in our own street tires.

Larry

[David Weaver]

FWIW, Costco routinely uses nitrogen to fill all the new tires, all brands, that they sell and install, nationwide. As savvy as Costco's management is, I doubt they were sold a bill of goods on the machines. ;)

David

I thought I would go out and read technical information (e.g., studies and data) regarding the nitrogen. It appears that the only practical benefit of nitrogen is if you fill your car tires with air and you never check the pressure. If you check the pressure of the tires on your car fairly regularly, there is no difference.

The other items that were quoted (rims rotting, tires rotting from the inside out, etc) don't appear to be real problems based on interviews of tires guys. (or as Ron White says, guys who went to Tire College).

Costco might have it just because people who don't know much about tires heard they should have it and demanded "that someone as concerned about their customers as costco should have these things, too", or they may feel that their target customers have a lot of potential for not checking their tires.

[Chris Parks]

I thought I would go out and read technical information (e.g., studies and data) regarding the nitrogen. It appears that the only practical benefit of nitrogen is if you fill your car tires with air and you never check the pressure. If you check the pressure of the tires on your car fairly regularly, there is no difference.

I think you need better reference material.

[Art Mann]

FWIW, Costco routinely uses nitrogen to fill all the new tires, all brands, that they sell and install, nationwide. As savvy as Costco's management is, I doubt they were sold a bill of goods on the machines. ;)

David

I think the Costco management is particularly savvy with regard to advertising gimmicks and they are not the ones who are sold a bill of goods.

[Mike Cruz]

Dennis, let me start by saying this: YES, I use nitrogen...but I use a mix. I use a special blend of about 78% nitrogen, 21% oxygen and 1% of other stuff. :D

Honestly, I understand the claims. Here's why: My understanding is that Nitrogen does not "escape" the tire as easily as Oxygen. Therefore, your tires will stay inflated to the proper pressure for "longer". What that gets you is proper performance from your tires. The pure Nitrogen itself doesn't not "perform" any better than "air". You will just tend to have a more even pressure over the life of the tire...supposedly.

Now, that said, I've had my '04 Chevy Silverado 2500HD for 10 years now (got it new). It came with Michelin MS tires. I got 80,000 miles out of those tires..."air" filled. At that point, I needed new tires. I got the same tires...Michelin MS. This time, I went with Nitrogen fill. At 170,000 miles, the tires were needing to be changed again. So, I got 90,000 on the second set. Was it because they were Nitrogen filled? I dunno. But I did get an extra 10,000 miles on them. That said, 10,000 miles ago, I WANTED to change them then. But because my wife and I just dropped $5K into fuel injectors (yeah, $4K jus for the parts...go look it up!!), I decided to wear them out juuuuust a little more.

Bottom line, in theory, yes, Nitrogen fill is better. If you have to pay extra FOR getting it, then it becomes debatable as to whether it is "worth" it. On that previous set that was Nitrogen filled, the dealership did it for free when you bought the tires from them. Though I DID get my tires from them again this time, I had them price match someone else, and while they did, they didn't fill my tires with Nitrogen. ;) Oh, well.

Hey, on another note, here is my "other" theory about how to Nitrogen fill your tires on your own... Fill you tires up with "air", say with 60 psi. You tires are now filled with 78% Nitrogen. When you tire pressure goes down, it is likely because the oxygen has seeped out. So, now your tire is at 45 psi. Fill it back up to 60 psi. Well, of the new "air" you just put in your tires, 78% of that is Nitrogen. So, you, in theory, should be up to about 89.5% Nitrogen. When your tire pressure falls to 55 psi, fill your tires up with "air" again. You will now be up to almost 95% Nitrogen!! And you did it for just about FREE. Yeah, I'm sure there are flaws in my theory, but on paper, it (might :rolleyes:) has merit!!!!

[ray hampton]

Do you understand how much water vapor is required to condense to two cups of water? Now try to get that same amount of vapor into an area the size of a tire. Good luck.



maybe the tire had a slow leak and require a inflate every day for a month or two, maybe that the compressor were full of liquid water and were forcing it into the tire , I was using a air tool and a fifty foot hose , the water kept dripping out of the tool, so you can tell me how much water will a compressor distill in a 8 hour day

[Mike Cruz]

Just run a dehumidifier in a 24 x 30 room and see the GALLONS of water that come out. And the air in there is NOT compressed...

[Rick Potter]

I just have to comment on how long a tire will hold plain old air. I have a trailer at my desert shack (5000' elevation), that I got from my in-laws in the 70's. I know for certain that no one has added air to the tires since 1963. It doesn't get used, and hasn't moved in 20 years, but the tires still have air, and that's with tubes. It started life as a 15', 1950's travel trailer. I hauled it to the dump, unbolted the body, rolled it over, and brought back the bare frame for future use that never came.

Anybody beat that?

Rick Potter

[Brian W Smith]

No Nitrogen here.

I'd be more inclined(for money saving purposes)to be giving cans of paint/stain/clears......a quick shot of Argon from our welding station when closing.

Another thought is about some AC(air comp)systems that are......ummm,lets say not all that well,setup.Again,with $$ on the line WRT time/materials in the spray booth.....having slop coming out of the airlines is costing money.

[Mike Cutler]

Largely,, I think it's a "fad" of sorts. I can see it for some very limited application, like the ones Chris Parks' referred to. For the everyday driver at highway speed, I don't see it. Maybe Indy cars, or NASCAR, or Formula One, or in Chris' case a KART, can quantify a difference, but not a regular car tire.
I've been "banging gas" since I was 19 years old and can fill my tires with 5.5 nitrogen any time I'd like too. I don't, air works just fine.

Don't believe that just because the N2 comes out of a cylinder, or that it is simply N2, and not just air, it's moisture free by nature or the process. Certified "dry" N2 is very expensive per cylinder and has very limited application. I highly doubt that anyone outside of racing teams could afford to buy a cylinder of certified dry N2. I've used one cylinder in my life and it was to inert the piping that held the mineral cables for a Nuclear Reactor Neutron flux Detector.

If a person wants to fill their tires with N2 though and believes there's a benefit, then there is for that person, same as the engine oil debates. I still change oil every 3-5K, but I know that technically the synthetic oil I'm using is good for a lot longer than that. I still do it though. It's peace of mind. ;)

Chris
I can dehumidify air to the same, or below, the values in the bottles you're sourcing, but it takes 100's of thousands of dollars to do it. Way more than a service center can afford to spend.

[Jason Roehl]

With regards to the claims of the size of nitrogen and oxygen molecules, here's a paper on the subject, for those so inclined to wade through it:

http://www.getnitrogen.org/pdf/graham.pdf

In short, it posits that the nitrogen molecule is indeed larger than the oxygen molecule.

[Mike Cruz]

Mike, at my dealership, they don't have "cylinders" of Nitrogen to fill tires. They have a machine (it is even painted green to signify that it is N ;)...makes it look all official), and for some reason, I don't think it simply has a/some cylinders of N in it. Not sure why, may have been that I could hear it running (maybe) or whatever, but I think that it simply processes air to separate out the N from the O and others, and most likely the water, too. This is totally a guess. But I just don't see them having a shell of a machine with cylinders inside them. Then again, maybe that is the marketing gurus at work...

[Alan Bienlein]

No. For me there is no benefit when I have a perfectly good air compressor in my shop to keep my tires properly inflated.

[Brian Tymchak]

There were a couple of posts discussing that a nitrogen filled tire is contaminated due to the trapped air in the tire. Was curious about that and googled around. Here's a couple paragraphs from a Popular Mechanics Q&A (http://www.popularmechanics.com/cars/how-to/repair-questions/4302788) about how nitrogen-filled tires are filled.


How is water relevant to a nitrogen discussion? Any system that delivers pure nitrogen is also going to deliver dry nitrogen. Filling tires with nitrogen involves filling and purging several times in succession, serially diluting the concentration of oxygen in the tire. This will also remove any water.

It's certainly simple, although time-consuming, for a tire technician to fill and bleed tires. But most shops use a machine that not only generates almost pure nitrogen by straining the oxygen out of shop-compressed air, but will also automatically go through several purge cycles unattended. Some shops have been charging as much as $30 per tire for this service. I think that's too much. If you're buying a new tire, it should be far less. Still, the nitrogen generator, filling system and technician's time aren't free—the dealer is entitled to some return for that.

[Stephen Cherry]

I just have to comment on how long a tire will hold plain old air. I have a trailer at my desert shack (5000' elevation), that I got from my in-laws in the 70's. I know for certain that no one has added air to the tires since 1963. It doesn't get used, and hasn't moved in 20 years, but the tires still have air, and that's with tubes. It started life as a 15', 1950's travel trailer. I hauled it to the dump, unbolted the body, rolled it over, and brought back the bare frame for future use that never came.

Anybody beat that?

Rick Potter

I'm going to show this post to the left rear tire on my pickup truck- it leaks the air out within a month or two, and I am really disappointed with it.

[Mike Cutler]

Mike, at my dealership, they don't have "cylinders" of Nitrogen to fill tires. They have a machine (it is even painted green to signify that it is N ;)...makes it look all official), and for some reason, I don't think it simply has a/some cylinders of N in it. Not sure why, may have been that I could hear it running (maybe) or whatever, but I think that it simply processes air to separate out the N from the O and others, and most likely the water, too. This is totally a guess. But I just don't see them having a shell of a machine with cylinders inside them. Then again, maybe that is the marketing gurus at work...

I only used cylinders in my post because that is more than likely the only "certifiable" N2 content that a "normal" person would be able to get a hold of.
The machine is scavenging off the O2 and compressing what is left. There may or may not be pre-dryers and desiccant towers inside, but there is most certainly and after filter/dryer cartridge.

Like I said though, if a person perceives a benefit from using N2, then there is for that person. It's their car and tires, not mine.

[dennis thompson]

I went to the Tire Rack site & they said:
"overall, inflating tires with nitrogen can't hurt & may provide some minimal benefits"
"rather than pay extra for nitrogen most consumers would be better off buying an accurate tire pressure gauge & checking & adjusting their tire pressures regularly"

[Phil Thien]

With regards to the claims of the size of nitrogen and oxygen molecules, here's a paper on the subject, for those so inclined to wade through it:

http://www.getnitrogen.org/pdf/graham.pdf

In short, it posits that the nitrogen molecule is indeed larger than the oxygen molecule.

Yeah, that is what I remember. I wonder why the chemists here are disagreeing, there must be something to TWO chemists saying nitrogen is smaller.

And in terms of your earlier post about nitrogen/oxygen dilution... My Odyssey has tire pressure monitoring on the dash. In the past, when I've had to have a tire patched, or recently when I had to replace all four tires, I experienced exactly what you are referring to. That is, a recently filled tire needs "topping-off" a few times, but then seems to hold whatever is in it (which I expect is mostly nitrogen).

[Art Mann]

The air/nitrogen/water vapor in a tire behaves according to Boyle's law. This law states that pressure is directly proportional to temperature, assuming a constant volume. Of course the volume of a tire is not exactly constant, but what this law means is that tire pressure will be significantly lower in cold weather than warm weather, assuming no air is added. The inverse is also true. I suspect this physical property has a lot more effect on tire pressure than the amount of oxygen diffusion or the amount of water in the tire.

[Mike Cruz]

Phil, straight disagreement between scientist over this may or may not be simple. Looking on the periodic table, N is what 7, and O is what 8? Wouldn't that inherently mean that N is smaller? I'm guessing not because someone posted a link to proof that N is bigger. Anyway, I don't know. I don't have that much desire to figure it out...

[David Cefai]

The size issue is more complex than discussed above. The Oxygen molecule has a double bond between the two oxygen atoms. The Nitrogen molecule has a triple bond. In simple terms this tendes to pull the nuclei closer together.

A simple explanation is here:
http://wiki.answers.com/Q/How_does_the_size_of_a_nitrogen_molecule_compare_t o_that_of_a_helium_molecule#slide1

However as even I stated earlier, the difference is small and would only matter in things like membrane separation (which is tricky and multi-stage because of the small differences).

[Brian Elfert]

Race car drivers can be very sensitive to the amount of pressure in their tires and of course they use nitrogen. With NASCAR we hear all the time about drivers requesting 1/2 PSI more or less in a tire. Not too many of us normal drivers would ever notice that little of a change in the PSI of our tires.

I don't use nitrogen in my tires. I did have a steel wheel fail internally on my motorhome a few months back. The wheel had cracked where the wheel had been welded. It was rusty at the crack, but I suspect the rust developed after the crack formed and was not the cause of the crack.

[Jason Roehl]

Another little factor here regarding the moisture in a tire. I just looked at a phase diagram for water. At 40 PSI, water doesn't boil until about 130ºC. That's a pretty hot tire--not unlikely on race cars or jets, but probably not very common on a civilian vehicle (although, I suppose it happens in the desert southwest). Here's something else--a tire tends to heat up more when it is low on air--that bulge near the bottom of a low tire is where a lot of flex takes place, causing heat, which means that any moisture in it would be more likely to turn to vapor, increasing the gas pressure in the tire.

So maybe a little moisture in a tire isn't a bad thing. Heck, tractor tires are often filled mostly with water as a way to add ballast! ;)

[Mike Cruz]

Yeah, Jason, but my tractor doesn't go NEARLY fast enough to cause friction to heat up my tires. ;) Actually, you know, think about a black tire out in the sun on a hot summer day. I would imagine the surface easily gets hot enough (and likely the internal air, too) to boil water. Maybe not... But if you can fry an egg on the hood of your car...:rolleyes:

[Curt Harms]

The air/nitrogen/water vapor in a tire behaves according to Boyle's law. This law states that pressure is directly proportional to temperature, assuming a constant volume. Of course the volume of a tire is not exactly constant, but what this law means is that tire pressure will be significantly lower in cold weather than warm weather, assuming no air is added. The inverse is also true. I suspect this physical property has a lot more effect on tire pressure than the amount of oxygen diffusion or the amount of water in the tire.

Yup. We just got a cold shot here - temp dropped from the 50s tothe 20s which is a big drop - the mid Atlantic states don't get the midwestern temperature swings. Tires that I keep at the recommended 32 psi were 25-27 psi. If you don't check tire pressure any other time (you should), check it when the weather gets cold.

[Brian Elfert]

I haven't been real good about checking tire pressures in my car tires. What usually happens when it gets real cold is the tire pressure monitor will go off one day. I used to get oil changes every 3,000 miles so the pressure got checked more often, but now I get almost 8,000 miles to an oil change. I am very good about checking the tire pressure on my motorhome, but that is probably because those tires each cost almost as much as a full set of tires for my car and can cause a lot of damage in a blowout.

[ray hampton]

Yeah, Jason, but my tractor doesn't go NEARLY fast enough to cause friction to heat up my tires. ;) Actually, you know, think about a black tire out in the sun on a hot summer day. I would imagine the surface easily gets hot enough (and likely the internal air, too) to boil water. Maybe not... But if you can fry an egg on the hood of your car...:rolleyes:

I not sure if a black rubber tire will heat up from the sun shine like a piece of steel will , but if you drive a car for a number of miles and get the tires hot then park on ice 6 inches thick, CAN YOU SAY STUCK

[Dennis Peacock]

Nitrogen is used in airliner tires and racing tires. For a typical civilian vehicle, nitrogen has one, and only one, purpose: to separate the civilian from more of their dollars.

I totally agree.

[Stephen Cherry]

I read up a little about this on the world wide web, and it turns out that tires, when severely overheated, can give off some gases, that can blow up in the presence of oxygen. This appears to be more of a truck or airplane issue, due to greater heat in braking of the possibility of stuck brakes.

This document, at page 6, gives a rundown on the process:
https://www.irsst.qc.ca/media/documents/pubirsst/r-590.pdf

[Mike Henderson]

I read up a little about this on the world wide web, and it turns out that tires, when severely overheated, can give off some gases, that can blow up in the presence of oxygen. This appears to be more of a truck or airplane issue, due to greater heat in braking of the possibility of stuck brakes.

This document, at page 6, gives a rundown on the process:
https://www.irsst.qc.ca/media/documents/pubirsst/r-590.pdf

Yep, if it was a real problem, we'd have a tire catching fire at least every day, given the number of tires on all the cars in the US.

Mike