Racing, moving to the next level Options

[Randal]

OK, all you big time racers out there, what is the correct procedure to purge air out of a tire before filling it with nitrogen?

The reason I ask is that any moisture mixed with nitrogen will create nitric acid, or some such vile stuff, if I remember correctly.

What about using air tools? Looks like a job for rubber gloves.

[SirAndy]

It is much easier to maintain consistan tire pressures when utilizing Nitrogen

ok, here are some numbers ...

At a temperature of 0°C and a pressure of 1 atmosphere, the densities of air, nitrogen and oxygen are:

Air: 1.293kg/m3
Nitrogen: 1.250kg/m3
Oxygen: 1.429 kg/m3

Notice the very small difference between good ole Air and Nitrogen?
less than 0.043 kg, that's a whooping 43 gram per m3 !

now, let's look at some more numbers, comparing Nitrogen and Oxygen:

	O2	N2
Normal boilingpoint at atmospheric pressure, oC	-183	-196
Ration of volume of gas tovolume of liquid, measured at  15oC and absolute pressure of 101.3 kPa	842	682
Relative density of gas at101.3 kPa and 25oC (Air = 1)	1.105	0.967
Liquid density at absolutepressure of 101.3 kPa, kg m-3	1141	807
Latent heat ofevaporation, kJ kg-1	213	199

mind you, we're actually interested in how AIR compares to Nitrogen, not Oxygen to Nitrogen, so we need to take the above numbers and put them into a 80/20 split in favor of the Nitrogen ...

bottomline, the expansion rate of pure Nitrogen gas compared to normal Air is about the same ...

now, that doesn't mean that someone can't make a shitload of money selling that stuff to racers who would sell their firstborn to get 1/100th of a second ahead.

flames on (IMG:style_emoticons/default/cool.gif) Andy