nitrogen in tires

[ckrug at indy.rr.com]

As a former tire tech for a large (4 car) racing team, here's my input on the nitrogen vs. air question.  There is ONE advantage to compressed nitrogen over air, and that is moisture content.  Air out of any compressor has a small amout of water vapor in in.  It's not enough to cause a corrosion problem, but what it DOES do is expand a lot more with heat than the rest of the gasses around it.   A racing tire filled with air will go up in pressure about 11 PSI  when it's hot.  The same tire using nitrogen (which is dry, decause of the way it is produced and bottled) will swell about 8 pounds.  Of course, your street tires don't see nearly the temperatures that a race tire does, so it's rather pointless.  Also, the other thing to consider is that when the tire store mounts your tire, they use regular air. When you request nitrogen, what to they do?  Just bleed off most of the pressure, then hook it up to the nitrogen bottle. What does that mean?  There's still a little bit of air and water in there.   On a racing tire, a big part of my job was taking every mounted tire, unscrewing the valve core, bleeding it down to almost zero, then filling with nitrogen, letting that bleed off again, repeating that 4 times to get as much of the air out of there as possible.  Sometimes we'd also use a vacuum pump and draw a vacuum on the tire until the tire collapsed.  I think if you tried that with a road tire, it would pop off the rim.  Why else do racers use nitrogen in their tires?  Well, compressors  aren't allowed on pit lane, so they already have large, high pressure nitrogen bottles to run the air tools and jacks.   That's how it started, surely, then they discovered that their tire pressures were more stable.
  So, here's my conclusion:  If you're getting tires for your commute to work, air is perfectly fine. Nitrogen is a gimmick.    If you are going to run a track day/ driving school, whatever, and want to keep the tire pressure more consistent through your sessions,  THEN go for the nitrogen.   

Calvin K.