http://action.publicbroadcasting.net/cartalk/posts/list/12202.page Public Action http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#967437 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#967437 GMT http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#963418 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#963418 GMT
It's not a matter of one or another gas being a by-product, the folks in the industrial gas business have processes to separate and sell all these gasses. Each individual gas is sold at it's market value, based on supply and demand.]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#963239 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#963239 GMT by product of oxygen production, nitrogen. If nobody needed pure oxygen, then pure nitrogen would be the product and pure oxygen would be the by product, something to be thrown away if nobody needs it.

It is quite possible that both oxygen and nitrogen are actually by products of argon production, an inert gas used in MIG and TIG welding.]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#963219 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#963219 GMT
The refrigeration cost to separate the gases is a large part of the purchase price, too.]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#962225 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#962225 GMT I can't, for the life of me, see how nitrogen could possibly decrease your tire's rolling resistance.
Nitrogen is cheap, it basically is a by-product of refining air into pure oxygen. If you didn't have a use for it, they would just have to release it back into the air anyway. The cost of this stuff is basically the cost of compressing it into cylinders and transporting it.]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#962015 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#962015 GMT http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#961612 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#961612 GMT - For all practical intents and purposes, as temperature increases all gases increase in pressure similarly.
- A few months back Consumer Reports tested nitrogen in car tires and demonstrated that it leaked out slightly more slowly than air. That said, what's the point? Unless the tires were evacuated before filling with the nitrogen, there's plenty of oxygen in there already, and adding air to the tires will add more. BTW, you should check your tires AT LEAST once each month and inflate (or deflate) them according to the standards listed on the sticker inside the driver's door jamb (NOT the pressure listed on the tire!!). Even if your tires never lost any air (which is highly unlikely!), you'll need to vent some pressure for the summer, and add some for the winter. That will end up adding plenty of air (i.e., gases other than nitrogen).
- Your sister should ask for her money back, and the mechanic who rooked her should be publicly exposed as a scam artist.]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#963033 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#963033 GMT http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#960282 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#960282 GMT http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#960248 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#960248 GMT
http://www...ry/02.html

The quick answer is that it isn't a problem unless you are a race car driver.]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#960245 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#960245 GMT The thing is, I'm pretty sure Tom and Ray dealt with this question, maybe a couple of months
ago in their Car Talk newspaper column. I don't recall exactly what they said, but am suprised
no one has so far mentioned it. (I think their bottom line was about what everyone seems to agree
on, that the difference is negligible and the cost a gyp.) As I have only disagreed with what they had to
say twice in all the years I've read them, I tend to trust their "lousy" answers.]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#960244 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#960244 GMT http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#960240 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#960240 GMT
I believe that is correct, both dry N2 and O2 will act about the same at these relatively low pressures and temperatures (close to an ideal gas), water/water vapor is the only real variable that is eliminated by using pure N2.]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#960247 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#960247 GMT http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#956822 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#956822 GMT
Both tire, and car manufactures set recommended tire inflation pressure based on cold tire pressure with the increase in pressure when the tire gets to operating pressure factored in. ]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#951034 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#951034 GMT http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#948011 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#948011 GMT http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#963048 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#963048 GMT
That is true, but just barely. The difference is so small that I doubt there is a measurable difference in diffusion through the tire or past mating surfaces. The covalent radius of nitrogen is 75 picometers; oxygen has a covalent radius of 73 picometers. Just double both values to get the length of the diatomic molecule. The difference is less than 3%.]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#948063 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#948063 GMT
Oh, and nitrogen won't feed a fire in the pits like oxygen would. That's why sanctioning bodies prohibit it.]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#947830 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#947830 GMT http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945267 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945267 GMT
I suppose that over time, oxygen might react with the rubber, but it should not be much. I believe that anyone using a nitrogen charge, like aircraft or race cars, does it to reduce burn potential as mentioned above. I see no particular reason for most people to use nitrogen only.]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945259 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945259 GMT http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945232 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945232 GMT And you asked about laughing gas. That's nitrous oxide, used by some dentists as a mild anesthetic. It is in no way related to the nitrogen used in those tires -- nor to the nitrogen in the atmosphere.]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945222 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945222 GMT
A couple of issues though, unlike aircraft tires which are purged of air when filling, most tire stores don't do this. They just pressurize the tire with nitrogen, so there will still be some oxygen in there. If you just use air to pressurize a tire and the oxygen slowly escapes, eventually the tires will have a high level of nitrogen, as air is 78% nitrogen.

One good thing about using N2 is that it is dry, no moisture like you usually get from compressed air. Some places use an air water separator on their air compressors, which helps.]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945217 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945217 GMT They burn well though.]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#950046 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#950046 GMT http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#947827 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#947827 GMT http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945216 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945216 GMT Tell your sister to forget this "footprint" garbage also as that ranks right in there with the nitrogen business.]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945018 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945018 GMT http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#944856 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#944856 GMT
They are, at least the questionable ones are.

2. My sister travels 2000 miles a year - how can she save $50.00?

Sure, over the next 50 years.

3. Isn't nitrogen part of a formula for laughing gas?

That is nitrous oxide. Different stuff.

4. Is the "Mechanic" blowing more than nitrogen?

Yea, some oxygen, carbon dioxide and a few other gases. Common air is about 80 Nitrogen. $30.00 is higher than I have heard anyone ripping someone off on this one. Many places do it for free with new tyres. The real cost is a few cents per tyre and unless the pull a vacuum on the tyre to start with they may have brought that 80% to 85%. ]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#944852 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#944852 GMT Will Nitrogen in my bicycle tires make it easier to pedal up hills?]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#966812 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#966812 GMT Norm--Could you kindly cite your source for "scientific" information of this nature?

(I'll save you the trouble. There is no source for this information since you are very mistaken about the properties of nitrogen.)  

Norms scientific knowledge (or lack there of) has been questioned a couple times here.]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#950032 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#950032 GMT "Nitrogen! Holy Crap! Get that nitrogen out of there before she takes a long trip and blows herself to the moon. I guarantee this will happen when the weather gets warmer. Nitrogen is very unstable when mixed with warm air. And, never go back to that shop again. Your sister is going to someday leave a "Footprint" that is like a moon crater unless you get that Nitro out."

Norm--Could you kindly cite your source for "scientific" information of this nature?

(I'll save you the trouble. There is no source for this information since you are very mistaken about the properties of nitrogen.)

]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#948044 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#948044 GMT
Just be sure that you don't use acetylene, though (it's the squatty black tank on your welding truck). Avoid the oxygen, too! If you see the guy roll out two tanks on a dolly, unhook his torch and hook up a filler nozzle, run away as fast as you can. She's about to blow, Scotty!! :D ]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#959229 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#959229 GMT
Nitrogen! Holy Crap! Get that nitrogen out of there before she takes a long trip and blows herself to the moon. I guarantee this will happen when the weather gets warmer.  

Nitrogen is very safe...Far safer then Normal Air because it doesn't contain oxygen.

However....it will NOT save you on gas mileage...It's a total waste of money. If they offered it for free (like many places do)..then fine..But to pay for it...no way no how.]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#948014 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#948014 GMT http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#947828 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#947828 GMT http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945021 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945021 GMT http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#944865 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#944865 GMT Anyone can improve their mileage by keeping the tires properly inflated. Ask yourself how many tanks of gas will it take, and what kind of driving will she have to do to achieve that $50. I bet it will be insignificant ]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#944849 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#944849 GMT http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945245 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945245 GMT
Nitrogen is used in aircraft tires because it won't feed oxygen to a brake fire if the tire should explode from the flames and heat.]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945214 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#945214 GMT
The mechanic is probably laughing about what all the way to the bank.

Nitrogen is used in large aircraft because of the change of atmospheric pressure and temperatures. It is a gas that under those conditions is more stable.]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#944846 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#944846 GMT If that mechanic had an M.D. degree, he would be called a "quack". Since he apparently lacks that sheepskin, the most polite term that I can come up with for him is Scam Artist. Once your sister realizes that she has blown $50.00, perhaps she will become more wary of obvious scams like this. ]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#944843 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#944843 GMT 1. Wouldn't the tire companies be touting this?
2. My sister travels 2000 miles a year - how can she save $50.00?
3. Isn't nitrogen part of a formula for laughing gas?
4. Is the "Mechanic" blowing more than nitrogen? ]]> http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#944841 http://action.publicbroadcasting.net/cartalk/posts/list/865814.page#944841 GMT