Nitrogen in tires, did I get hosed?

[EMB135Driver]

Originally Posted by CWIweldace

69% of atmospheric air IS nitrogen, 20.5% oxygen and the rest is other inert gases. I don't see where putting 100% nitrogen would change the expansion rate significantly. I also don't see where the small percentage of overall volume of humidity in compressed air is significantly a factor. And green stem caps? WTF?

I don't want you to worry, because I have no intention of contacting your High School Chemistry teacher, but the Atmosphere is approximately 78% Nitrogen, 21% Oxygen, and 1% other gasses.

[Kwaz1335]

I learned this while working for a race car team at a local track after getting ripped off. There is still going to be air in your tires unless they purge them of air completely. They do this by filling up the tire with nitrogen then draining it by pulling the core. The process is repeated a few times then the core is returned to the stem while the tire is being drained the final time. The tire should be brought up to pressure with nitrogen after this process is completed. Just draining a tire and filling it with nitrogen saves money but it dose not drain the tire of air.

[DkknightX]

Originally Posted by Morepwr

Shoulda used helium!

He should have used Methane.

[squat]

Yes sir, you did indeed get hosed.

[Ghost Rider]

I was told that nitrogen won't leak out of the tires as quickly as regular air because nitrogen molecules are larger than oxygen molecules. They did say they can't completely get the oxygen out but the ratio is about 95% nitrogen.

[78camaro]

Here's a lesson: Whenever a dealership wants to sell you something, say "no." If it sounds like a good idea, go home and find it cheaper somewhere else. If you don't understand what they are talking about (ie., the chemical composition of the air in your tires, rust proofing, and other crap like that), just forgedaboudit.

[Adam]

Those of you that said I got hosed and didn't say anything else, go to hell for being worthless posters.

No one tried to sell me anything. Stupid news said it didn't fluctuate, so I initiated it with the dealer.

I was under the apparently false assumption that it just didn't expand or contract the way oxygen did. It's really annoying for onstar to email me or the car to tell me my pressure is too low. If it's impossible to stabalize it due to outside temperature and tires heating up then the car should just stfu about it.

[Brokinarrow]

Originally Posted by Adam

Those of you that said I got hosed and didn't say anything else, go to hell for being worthless posters.

No one tried to sell me anything. Stupid news said it didn't fluctuate, so I initiated it with the dealer.

I was under the apparently false assumption that it just didn't expand or contract the way oxygen did. It's really annoying for onstar to email me or the car to tell me my pressure is too low. If it's impossible to stabalize it due to outside temperature and tires heating up then the car should just stfu about it.

Well, unless scientists have suddenly made/discovered a gas that DOESN'T expand and contract with changes in heat (and then named it Nitrogen), your tire pressure will ALWAYS fluctuate, no matter what. It's just a matter of how much the pressure will vary. Remember: about 75% of normal air is nitrogen. While your tire pressure will change, the added nitrogen will have a harder time escaping, so your tires should stay inflated longer. Therefore, the tire holds its correct shape longer and gives you better tire wear

[MontyCarlo]

Behold, I come bearing math!

P*V=n*R*T
(Pressure, Volume, # of gas molecules, ideal gas constant, and absolute Temperature)

Volume, # of molecules, and R are fixed & unchanging in your tire.

That leaves you with "Pressure is directly proportional to absolute temperature."

The difference in absolute temperature between a winter night and a summer day is around 15%, so when your car's at rest, you can expect a 15% difference between winter tire pressure & summer tire pressure, disregarding leaks.

[camarossrs2150]

how much did that cost

[Brokinarrow]

Originally Posted by CWIweldace

69% of atmospheric air IS nitrogen, 20.5% oxygen and the rest is other inert gases. I don't see where putting 100% nitrogen would change the expansion rate significantly. I also don't see where the small percentage of overall volume of humidity in compressed air is significantly a factor. And green stem caps? WTF?

They usually put those on so that if you take your car somewhere else to get serviced, they will know the tires have nitrogen in them and not to add normal air.

[Brokinarrow]

Originally Posted by MontyCarlo

Behold, I come bearing math!

P*V=n*R*T
(Pressure, Volume, # of gas molecules, ideal gas constant, and absolute Temperature)

Volume, # of molecules, and R are fixed & unchanging in your tire.

That leaves you with "Pressure is directly proportional to absolute temperature."

The difference in absolute temperature between a winter night and a summer day is around 15%, so when your car's at rest, you can expect a 15% difference between winter tire pressure & summer tire pressure, disregarding leaks.

Noooooo, not Math! *hisssss*

[mulletman]

Just check and adjust the air pressure at night when the temperature is the lowest.
I have noticed a difference in air pressure between the sunny and shady sides during
the day.

[Rickey]

I had nitrogen put in my tires too, and my pressure is not changing. The temps here have not gotten much below freezing nor much above the mid 50s since I put it in but the pressure has stayed at 39psi. I was charged $40 and it is good for free refills as long as I own the car.