Re: At 0 degrees my hybrid doesn't work well
 

I can't refute the referenced universal gas law reference because it's been 30 yrs since my physics classes and I am not familiar enough with it one way or the other. I'll take your word.

Is there something else though? Why then do the tires not expand and contract as much when nitrogen is used as opposed to normal air? Is there something about the use of it in NASCAR that contravenes the gas law? From a brief explanation I was given the nitrogen molecules are larger than air. When heated from driving ( friction ) they don't expand as much as air molecules. When cooled down they don't contract as much.

I'm always open to learning something new so any additional explanations would be appreciated.

An obviously biased source, but interesting..
http://www.getnitrogen.org/

Here is a good discussion for a neophyte like me..
http://www.eng-tips.com/viewthread.c...=120996&page=1

Re: At 0 degrees my hybrid doesn't work well
 

Air is 78% nitrogen, btw.

Some discussion on whether using nitrogen offers any benefit or not. Your linked discussion indicates nitrogen is used because it comes in pressurized canisters, meaning you don't need a compressor (as you would if you used the ambient air).

Re: At 0 degrees my hybrid doesn't work well
 

Put a little helium in them, you will just float along,ROTFFLMAO:D :D

Re: At 0 degrees my hybrid doesn't work well
 

kdhspyder — I've also seen some of those claims for the benefits of nitrogen in tires, but I think that most of their claims are bogus science. Nitrogen and oxygen both expand similarly, and so I can't accept your statement:
"... nitrogen molecules are larger than air. When heated from driving ( friction ) they don't expand as much as air molecules. When cooled down they don't contract as much."
However, there may be other relevant factors. For example, water vapor in the air might change the pressure-vs-temperature behavior a bit, and nitrogen generators would almost certainly produce dried gas, whereas normal air pumps probably don't dry the air. If that's the case, drying the air would be a simpler and cheaper solution. It's also possible that the heat conduction from the tire to the rim might be higher with nitrogen. I don't know. Until we (i.e., you!) find a plausible explanation, I remain a skeptic.

Stan

Re: At 0 degrees my hybrid doesn't work well
 

You could make the case the larger nitrogen modules might permeate the rubber of the tire less, thus reducing pressure loss over extended time, but I doubt the amount would come close to justifying the cost/effort.

Re: At 0 degrees my hybrid doesn't work well
 

Loonbeam — Yes, that might be true. On that basis, the concentration of nitrogen inside the tire would automatically tend to increase with time. Does it do so? Maybe, maybe not. What are the facts?

Stan

Re: At 0 degrees my hybrid doesn't work well
 

On the next set of tires which should go on my Prius sometime mid next year I will do a real world anecdotal test on nitrogen filling. The main problem is that I don't have any control data to compare it to.

From what I read in the two links I posted it does seem that eliminating the water vapor in normal air is a key reason for using the 'dry' nitrogen. Since it can't hurt and might help I will take the plunge. Sort of like buying a hybrid.;)

Re: At 0 degrees my hybrid doesn't work well
 

Actually it wouldn't, given that there is no way for additional nitrogen to enter the tire (or are you referring to the oxygen/nitrogen ratio?).

Anyway, as far as facts per say, I don't have any having not done any scientific research on it. That said, I did ask a relative who is a college chem professor and he indicated (again, without rigorous research) that it is at least materially feasible that nitrogen would escape the tire at a minimally smaller rate (there is always some air loss due to general osmosis and seal flexing, but that the difference would most likely to be so small as to be unnoticable by most equipment. His theory was that if an average tire loses 1.0 psi (numbers pulled out of the air) per month, a nitrogen filled tire might lose 0.999 psi in the same period.

Re: At 0 degrees my hybrid doesn't work well
 

By the way, the atomic number of nitrogen is 7 and oxygen is 8. So, their molecular weights would be in the ratio of 14 to 16. Oxygen is thus a heavier molecule than nitrogen. I think this blows the "nitrogen is a bigger molecule" theory.

Stan

Re: At 0 degrees my hybrid doesn't work well
 

Asked about that, apparently the arrangement of the molecular structure in nitrogen is more spacious and thus has a slightly larger physical size, mass notwithstanding (again, we're missing the overall point here, the difference is so minute as to produce a negligible effect, at least for this)

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