I know there are mixed feelings about Nitrogen being a gimmick while some say it actually is better. I wanted to ask if anybody tried using Nitrogen in their track tires?

 

Not a gimmick. Nitrogen is dryer than normal air so it is less affected by temperature and will keep your tire pressures more stable.

 

Gimmick. You will not notice any difference in tire pressures between the two.

 

i use CO2

 

The only difference is in how much air will leak out since nitrogen is a larger molecule.

All gases still expand due to heat.

 

At Porsche Motorsport for years we wasted our money on it.

 

Right, and since its for race tires, this will never be an issue.

 

l8brakr has it right.

Regular [dry] air is about 80% N2. There's no significant difference between using dry air and pure N2 except that won't support combustion.

But dry air is hard to find. Air readily accepts water vapor. And it's the water content in the tires that really exagerates the pressure changes as the tire heats up. Even more importantly, since the water content varies, it means that it makes it hard to predict exactly how much the pressure will change on a race tire. If the water is all vaporized then it's not really an issue, since it is a gas just like any other gas. But if some of the water is condensed into liquid, then when it heats up it will expand into gas. This liquid->gas conversion has a much bigger effect on pressures than just heating up a gas would have.

It's fairly easy, though, to manufacture dry N2. No harder than dry air, anyway. It's the "dry" part that makes a difference.

Where they are allowed, though, you could just use pressure relief valves on your wheels. That keeps the pressure constant through an entire session.

 

My understanding was that the water vapor in normal air does not obey the ideal gas law, which is why dry nitrogen is more consistent in its expansion characteristics.

 

Nitrogen is not any more "dry" than CO2, O2 or f-ing methane. It's just that if you're getting your gas from a dry source, it will be dry by comparison to compressing regular air out of the atmosphere where there is always humidity.

Anyway - it's not going to matter. If you have a nitrogen source around, go ahead and use it. If you don't, don't drive to costco just to fill up your tires.