Nitrogen Filled Tires

I just bought my wife a new bike since her other ones are well used. Interestingly, the dealer filled her bike tires up with nitrogen. I know all the good things about nitrogen filled tires but I was wondering how easy this will be for me to maintain pressure on a regular basis? Where can I get nitrogen other than the dealer? I use a compressor in my garage and with 6 motorcycles, I am pretty conscientious about our tire pressure and other maintenance issues, since I do most work myself.

Anyone use this and care to clue me in on how you maintain pressure?

Thanks in advance for replies.

It should be fine to top them up with regular air. It's not like the tires were mounted to the rims in a nitrogen filled room, so there's regular air in them anyway.

If you want your own nitrogen, the first place I'd look would be a welding supply store. You might be able to get a small bottle from them, something like the size of an oxygen bottle emergency crews use.

nitrogen - Is that some kind of a bomb? Any Radiation effects?

Top up with regular air (which is around 70% nitrogen anyway) and don't worry about it. One of the benefits of nitrogen is not having to top off often and since the amount of non-nitrogen you add will be so tiny compared to all the nitrogen that is already compressed in the tire, it is doubtful it would have any real effect within the life if the tire.

Thanks for the information! I may even stop by the dealer to ask them to fill my tires up just to see if I notice a difference in ride. Unless it's expensive to do that.

Nice wife's car came with nitrogen filled tires when we bought it. I used to care about getting them filled back up with nitrogen, but I think in my area Costco is the only place that uses nitrogen. So with two compressors in my garage the choice was simple, I use my compressor from then on. Never noticed a difference at all. Like Mike Cash stated, our atmosphere is mostly nitrogen anyways. It's only 20.9% oxygen, the rest is mostly nitrogen.

Regular dry air is 78.09% nitrogen anyway.

I'm pretty sure nitrogen filled tires is a scam.

My understanding is that the benefits of N2 vs regular mixed air is that N2 is a bigger molecule so it leaks out slower...
If this is true, CO2 is a larger molecule still, and should leak out even slower, but we aren't all topping off our tires with CO2 cartridges... (though you can get them for emergencies)
Of course the difference is minimal... and really if N2 leaks out slower and standard air is ~75% N2 then the 25% of air that leaks out of our tires first would be the O2 and subsequent fill ups would leave us with higher and higher concentrations of N2 in our tires, for free!

The real benefit of N2 over air is that the N2 doesn't contain water or water vapor. The danger of water is it condensing in your tire at cooler temps and expanding at higher temps, meaning that as your tire warms up the pressure goes up. Of course since we all know that the tire pressure is for warm tires wouldn't be risking blowing a tire or anything just worse gas milage until we warm up our tires.

Just put in dry air (cooler air is usually drier air, so let your compressor fill the tank, let the tank cool down, then top off the tires, then drain the water out of the tank) and you'll get most of the benefits of nitrogen...

As a 22 year Navy aircraft mechanic I can say this.... Nitrogen (dry) is all that is used for naval aircraft tires. Two reasons, less potential for oxidation (corrosion) of rims and tires & thermal stability. Nitrogen doesn't expand/contract with temperature changes as ambient air. Aircraft tires change temperature rather rapidly during landing/braking. Some trucking companies are switching to nitrogen for the tires in their fleets as well. Just my two cents!

Steve

Here's a link to the truck research: http://www.getnitrogen.org/pdf/Nitrogen%20Tire%20Inflation%20for%20the%20Big%20Rigs.pdf

Suddenly, I feel kind of dumb! I know a lot more about tire air than I did 2 hrs ago. Thanks all.

I thought all gases experienced a pressure change with a temperature change (and vice-versa).

Gas Laws

True, adding heat makes all the molecules dance around a little more and take up a bit more space. Nitrogen just doesn't dance as much as the rest under the same conditions as regular air. In consumer car tires I think it's a bit of a joke. Not enough heat change to notice any difference. As has been said before, in aircraft tires it's a different story. I had to change all four main wheels on a King Air 200 one night because the pilot landed with his feet on the brakes. Mega flat spots, it was like counting rings on a tree trunk. If they had regular air in them instead of nitrogen who knows, they might have blown and we'd have been into a much dirtier mess than just changing tires.

Nitrogen has its place, but not in my tires.

Mike Cash said:

I thought all gases experienced a pressure change with a temperature change (and vice-versa).

Gas Laws

Click to expand...

They do, and nitrogen is no different, though if there is water in the equation then you are dealing with a phase change into a liquid (potentially) which will cause a larger shift in pressure.

Nitrogen is used on things like aircraft and space shuttles because it is pretty much always a gas at the temperature and pressure they are using it at.
According to NASA the space shuttle tires are inflated to 340 PSI which is a point where state change might be induced in CO2 and filling your tires with dry ice is probably a bad plan.
Oxygen wouldn't have that problem, but it does have the issue of being one of the required items for a tire literally exploding (fireball not pressure leak).

Looking at the phase change diagrams on wolfram alpha, there isn't any difference around phase change for the stuff in the atmosphere at the temperature and pressures we are looking at (save maybe water.)

manchinator said:

As a 22 year Navy aircraft mechanic I can say this.... Nitrogen (dry) is all that is used for naval aircraft tires. Two reasons, less potential for oxidation (corrosion) of rims and tires & thermal stability. Nitrogen doesn't expand/contract with temperature changes as ambient air. Aircraft tires change temperature rather rapidly during landing/braking. Some trucking companies are switching to nitrogen for the tires in their fleets as well. Just my two cents!

Steve

Here's a link to the truck research: http://www.getnitrogen.org/pdf/Nitrogen%20Tire%20Inflation%20for%20the%20Big%20Rigs.pdf

Click to expand...

The nitrogen will still expand and contract as all gasses do. Boyle's Law is Boyle's Law. The reason for filling with nitrogen is that it's guaranteed moisture and oil free. Oil free is good but moisture free is important for aircraft because when an aircraft is flying high it can get well below freezing. This can cause condensation and result in ice buildup in the wheel which can cause paint and coatings to flake off because of ice expansion. Then the moisture plus high tire air pressures can cause corrosion issues subsequently.

Being a Flight Engineer as well I'm familiar with the principles of Boyle's Law. Should have said "not as much as ambient air" (due to moisture content).
My apologies,.... Something from the FAA.

Federal Aviation Administration


Airworthiness Directive

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

Amendment 39-5613; AD 87-08-09

Airworthiness Directives; AIRBUS INDUSTRIE, BOEING, BRITISH AEROSPACE, LOCKHEED, MCDONNELL DOUGLAS; specified models
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AGENCY: Federal Aviation Administration, DOT

DATES: Effective June 1, 1987.

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To eliminate the possibility of a chemical reaction between atmospheric oxygen and volatile gases from the tire inner liner producing a tire explosion, accomplish the following, unless already accomplished:

A. Within 180 days after the effective date of this AD, to ensure that all aircraft tires mounted on braked wheels do not contain more than 5 percent oxygen by volume, accomplish paragraph 1. or 2., below. Either of these procedures is acceptable, or they may be used together:

1. Install a placard, either in each wheel well or on or near each landing gear strut incorporating braked wheels, and in a location so as to be easily seen and readable by a person performing routine tire servicing. This placard shall state "INFLATE TIRES WITH NITROGEN ONLY." The words "SERVICE" or "FILL" may be substituted for the word "INFLATE".

2. Incorporate into the FAA-approved maintenance program procedures that include the following items:

a. On braked wheels, install only tires that have been inflated with dry nitrogen or other gases shown to be inert such that the gas mixture does not exceed 5 percent oxygen by volume.

b. Tires on braked wheels may be serviced with air at remote locations where dry nitrogen is not available, provided that:

i. the oxygen content does not exceed 5 percent by volume; or

ii. within the next 15 hours time-in-service, the tire must be purged of air and inflated with dry nitrogen so that the oxygen does not exceed 5 percent by volume.

B. An alternate means of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region (Airbus Industrie, Boeing, and British Aerospace models); or the Manager, Los Angeles Aircraft Certification Office, FAA, Northwest Mountain Region (Lockheed and McDonnell Douglas models).

C. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base for the accomplishment of the modification required by this AD.

This Amendment becomes effective June 1, 1987.



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When I was in kindergarten my mother got a phone call from my teacher. Seems the teacher asked me a question, and I told her that I could never answer a complicated question like that. The teacher asked me what made this question complicated, I told her that if this was not a complicated question I would already know the answer, and if she would just give me the answer it would be a simple question. Everything is simple once we know the answer!

670cc said:

Regular dry air is 78.09% nitrogen anyway.

Click to expand...

Great news! that means I'm 78.09 % on top of this one!

(I use a bicycle floor pump to check pressure and top off)

Any serious cyclist will confirm that CO2 leaks out of tires far faster than air. When I get home, after filling my flatted tire with CO2 from a cylinder at the roadside, I let all the CO2 out and refill with air so that I don't have a soggy tire next day. I don't understand the physics of this but it is so.

Googled it; here is the answer. It turns out that there is a complex interaction between the electrical forces binding the atoms together that affects the overall size of the molecules. Because of that, the atoms in CO2 are confined to a smaller space than either O2 or N2 even though CO2 has more atoms! But even more importantly, CO2 is electrically attracted to the rubber molecules, drawing them into the interstices while O2 and N2 are repelled and must be forced through. This means that carbon dioxide very effectively dissolves into butyl rubber and evaporates out the other side.

Manufacturers of gas products often use what is called a molecular sieve to separate nitrogen, oxygen and carbon dioxide from air. A bike inner tube makes a pretty good molecular sieve. Pure oxygen will leak out of a tire 3-5 times faster than pure nitrogen, because of oxygen’s smaller size. But carbon dioxide will leak out much faster than that, up to 12 times faster than nitrogen.

longhorn said:

Googled it; here is the answer. It turns out that there is a complex interaction between the electrical forces binding the atoms together that affects the overall size of the molecules. Because of that, the atoms in CO2 are confined to a smaller space than either O2 or N2 even though CO2 has more atoms! But even more importantly, CO2 is electrically attracted to the rubber molecules, drawing them into the interstices while O2 and N2 are repelled and must be forced through. This means that carbon dioxide very effectively dissolves into butyl rubber and evaporates out the other side.

Manufacturers of gas products often use what is called a molecular sieve to separate nitrogen, oxygen and carbon dioxide from air. A bike inner tube makes a pretty good molecular sieve. Pure oxygen will leak out of a tire 3-5 times faster than pure nitrogen, because of oxygen’s smaller size. But carbon dioxide will leak out much faster than that, up to 12 times faster than nitrogen.

Click to expand...

Well then on that logic, should not the percentage of nitrogen in the tire's air continue to increase as you continue to top off the tire to replace the lost O2 and CO2? Eventually you end up with nearly all nitrogen (along with maybe some Argon and other stuff), which seems to be the goal here. No?

Greg