air vs nitrogen in tires...

[JamesB]

Pretty much, I dont like any self oiling systems either because it gunks up the hoses. But just a quick drop or two for every hour of use so far has kept all my tools happy.

BTW, I was up getting a new bottle for my stainless mig so I asked the guys if I did a 160lb nitrogen bottle to use at the track for air tools and whatnot would I need to run with a placecard. He told me DOT and MDOT (maryland) laws go by weight and they said over 500lbs you need to run a non-flammable, over 1500lbs you need a HAZMAT before they will even sell you that many bottles.

He said the rules for VA and WVA are the same but he doesnt know about if other states have renched down on the DOT information.

[Domino]

Does anyone have any solid data that switching to N2/dry air vs ambient air will significantly reduce psi flucuations? This weekend at Roebling I was experiencing variations of 15 psi in the front and 10 psi in the rear (FWD 225 Hoosiers). The link below would suggest that it does not. But then again the discussion is based on some opinion and some physics calcs with no real world application.

http://www.eng-tips.com/viewthread.c...=120996&page=1

[joeg]

Humidity is key.

Also, unless you are able to mount the tire with Nitrogen (or somehow evacuate all the air so used for that purpose) you do not get that great effect .

[Domino]

With regard to humidity, H20 in a vapor state should still follow the PV=nRT rule meaning that water vapor would react the same as a dry gas. There is so much conjecture out there that I just wanted some first hand knowledge before I dropped $200 on a cylinder and regulator.

[turboICE]

The thing is the system can not be evaluated by the ideal gas law. It is too complex with feedback mechanisms.

Doing so presumes that the gas temperature for a tire filled with commercial nitrogen and another with wet air will abosorb and release heat from the system at the same rate. All you need is for the humidity in the air to more readily absorb heat into the system and less readily release it and the temperature of the gas in the wet air tire is higher than the commercial nitrogen. Once that happens the pressure is higher, once the pressure is higher the feedback of pressures and temperatures in the system are completely different between the two. (And the characteristics of water vapor vary quite a bit with pressures IIRC.)


We aren't talking about containers where the gasses are heated from the same static temperature and pressure to the same higher static temperature raised and maintained in a controlled environment and then the pressure change from original is measured.

[AntonioGG]

This is a good read:

http://forum.specmiata.com/cgi-bin/ultimat...0009;p=0#000000

[ITA_CRX]

I used Nitrogen for the better part of a year. You don't need to vacuum out the tires. Just deflate them then over fill them. I was running my tires in the ~31 PSI range so I put 45 PSI in, then deflated them down to the level I wanted before I went on track. That will get most of the water out and it'll work almost as advertised.

My experience was that it was about half the pressure increase relative to air. So instead of starting with 31 PSI for air I started with 34 PSI for Nitrogen to get to a hot pressure of 37. I never noticed a big enough on track difference to say it was worthwhile.

One thing I did note, with Nitrogen it was a lot harder to warm the tires on cold days. I had a morning qualifying session in the fall where the rear tires never developed any grip and I ended up stuffing it in the wall. I think I had run 5 or more laps before I crashed.