It's an old racer trick, but is predominantly used because it offers much more stability and predictability in regards to the tire temperature, which is crucial in a performance application.

I can't really see it improving gas mileage.

I don't think my tires really heat up all that much when I do hot laps to and from the grocery store, and in 30mph rush hour traffic.

 

is there any probs mixing nitrogen filled tires with regular compressed air? I noticed they have green caps on mine, but I want to put in more pressure.

 

No, but generally what is done is they deflate your tires and reinflate them with nitrogen the first time out. You will not get any benefit by adding some nitrogen to air already in the tire.

What I did the first time I did the nitrogen is check them after the tires cooled down after being out on the road to see the psi. I would add just enough air, like 1 psi, to make sure the fronts were 39 and the rears were 38. It is kind of one of those things like measuring ATF or coolant after doing a drain and fill.

 

how do you like the ride at those PSI?

 

It is not too bad, the bumps are a little harder (of which we have an infinite number down here), but the combo of 39/38 works best on the track. Keep in mind those are cold numbers, but I only seem them jump about 1psi upward at the track, so less rolling resistance. The front I keep it 1 psi higher due to the engine weight on the front and the slight lift off the launch.

If I go too high on the psi (tried it several times) it seems like it skips or floats down the track...almost like a sense for a second of no traction.

 

Maybe they got helium instead of nitrogen . . .

It seems like the first advantage of N2 is that it's dry. Without the water vapor present in most compressed air systems, your tire pressure will remain more stable from cold to hot. Also N2 is an inert gas, prolonging the life of the tire compound - at least on the inside of the tire.

 

Actually, a few people at my track have been looking for helium thinking their will be these huge unsprung weight gains.

Can you imagine, "Well he did darned good on his LAUNCH, but we are not sure when he will finish the race as he floating somewhere around cloud 9 right now."

 

Autobac in Japan has offered nitrogen for a while and I have done it in the past for some of my vehicles as well. Works good but works best when you have a wheel with dual valve stems and they have the right machine that can purge as much of the normal air out of the tyre as possible.

 

The place where I get my nitrogen down here is looking for that, because some air always remains despite deflating the tire.

 

They need to watch the Mythbusters episode on footballs filled with helium flying farther. They will be disappointed!

 

It's the pressure increase due to heat that the racers and airplane guys want to avoid. It is a result of the heat generated by the moisture in the oxygen.

Edit: Just noticed. A little over 5 years and I got to my 1,000th post. Watch out Richie! Rominl I think you are safe!