Airing Down Nitrogen Filled Tires

[Lindenwood]

Fair enough. Do you know what the expansion rates are? Nitrogen must just be less thus the perceived benefit.

The difference between pure "air" and nitrogen is negligable. The key difference is water vapor. Water expands something like 40 times going from liquid to gas. Thus, at ambient Temps, some of the water in the tires may actually condense into tiny droplets (that may even be suspended in the air in the time). When heated, some of those droplets turn into vapor, increasing pressure beyond what is reliably predicted.

Consider a NASCAR race, where tire Temps might reach 175 degrees. This big temp difference means what might have only been a predictable (hypothetical) 10 PSI increase may be anywhere from 11-15 PSI increase depending on the relative humidity of the ambient air when the tires were filled. In a race car that spends minutes or hours cornering at the absolute limits, this level of uncertainty (did they go up 11 PSI or 15 PSI?) could easily be noticeable to the driver.

In a passenger car on a highway trip, where tire Temps may only hit 20-30 degrees above ambient instead of perhaps 60-80, fewer of those water droplets evaporate, which means there is a smaller varience. What might have been a 4 PSI increase with pure nitrogen is now somewhere between, say, 5 and 6 PSI.

I can say with great confidence that none of us would notice a 1 or 2 PSI varience in our street vehicles.

 

[Dilldog]

The difference between pure "air" and nitrogen is negligable. The key difference is water vapor. Water expands something like 40 times going from liquid to gas. Thus, at ambient Temps, some of the water in the tires may actually condense into tiny droplets (that may even be suspended in the air in the time). When heated, some of those droplets turn into vapor, increasing pressure beyond what is reliably predicted.

Consider a NASCAR race, where tire Temps might reach 175 degrees. This big temp difference means what might have only been a predictable (hypothetical) 10 PSI increase may be anywhere from 11-15 PSI increase depending on the relative humidity of the ambient air when the tires were filled. In a race car that spends minutes or hours cornering at the absolute limits, this level of uncertainty (did they go up 11 PSI or 15 PSI?) could easily be noticeable to the driver.

In a passenger car on a highway trip, where tire Temps may only hit 20-30 degrees above ambient instead of perhaps 60-80, fewer of those water droplets evaporate, which means there is a smaller varience. What might have been a 4 PSI increase with pure nitrogen is now somewhere between, say, 5 and 6 PSI.

I can say with great confidence that none of us would notice a 1 or 2 PSI varience in our street vehicles.

OK, sounds like I had the right idea I was just using incorrect terminology, and not being complete in my explanation. Anyway I agree that unless you are competing at a high level it doesn't matter.

 

[Downs]

I think you'll be fine going with regular air. A good air drier on a compressed air system will get as much moisture out as you need.

 

[ThundahBeagle]

Nitrogen in our tires is a "princess and the pea" situation. Please dont be that princess