Originally Posted By: Stewart Fan
I can't help but wonder how many people get suckered in to this deal.
I think Nitrogen is a good idea, but it is indeed absurd to pay $50/tire. Some dealers offer it for free (like my local Toyota dealer) and I hear some Costco tire stores also offer it for free. I buy a small cylinder of Nitrogen which lasts me about a year (car, bike, etc.) and only costs about $20 to exchange for a full one when empty.
Here are my thoughts on the matter which I posted in another thread:
Originally Posted By: gaijinnv
Originally Posted By: geeman789
Originally Posted By: brslds
Change them over to nitrogen too.
"Regular..." air is almost 80% nitrogen already... and "pure..." nitrogen (not that your getting that...) still expands and contracts, and leaks, albeit ever so slightly slower...
Your tire pressure will still change with temp and time...!
You're right, air is 78% Nitrogen, but that's not why Nitrogen performs better in tires than air.
Virtually all air that is used to fill tires contains moisture - more or less depending on how the compressor is set up and how diligent the maintenance on it is. The time of year (ambient temp) and climate (humidity) can also affect the amount of moisture in air used to fill a tire.
Nitrogen, on the other hand, does not contain any moisture (OK, OK, way less - virtually none).
All gases expand and contract with changes in temperature. Most, including Nitrogen and Oxygen, both expand and contract about the same amount in accordance with the ideal gas law.
What does not expand and contract at the same rate is the moisture. Moisture (water vapor) expands about 7 times more than Nitrogen and Oxygen. It is the presence of moisture in the tire that causes exaggerated pressure differences when a tire heats up on the highway and cools down overnight in the winter.
Less moisture in a tire means less difference in pressure due to temperature.
The worst thing you can put in your tires is the air from a gas station - loaded with moisture.
So ... if you want the most consistent pressure in your tires over a wider range of operating temperatures, Nitrogen should be your gas of choice.
HTH