R36 - Nitrogen

[G-rig]

Yeah it's like bottled (tap) water & san pellegrino.

[Rocket36]

I won't run anything but nitrogen in Canberra. One of the biggest temperature ranges in Australia. Down to -10 in winter (or colder) and over 40 in summer. The reason planes have only used nitrogen for decades is mostly because its volume barely changes based on temperature compared with air. Means pressures are more consistant across all temperature ranges. And that's really the only benefit - more consistant pressures regardless of temperature.

[richdave]

the only benefit - more consistent pressures regardless of temperature.

And that is only because "air" is not dry whereas Nitrogen is.

Put dry air in and you wont know the difference between the gasses...

[G-rig]

It's more consistent until the tyres heat up.

[Swallowtail]

It has been drawn to my attention that my post questioning Preen58's post was probably poorly put, and that whilst his response which got him banned for various forum rules breaches cannot be justified, he may have felt that I was having a go at ridiculing his comments or experience. So for the record - that was not my intent, and I apologise if that was how the post came over.

Final comment - we are supposed t be adults, if somene says somethng that offends you, gets your back up or you strongly disagree with, this forum has an excellent PM system, please use it and try and resolve issues offline.
Thanks
swallowtail.

[Maverick]

Sorry Maverick, but while Nitrogen has a lower molecular weight, 28 Vs O2 with 32, the molecule size is actually larger thus it does not permeate thru the rubber walls as fast as O2.

And the science behind it...Link

Thanks but my head hurts after reading that!

Here's part of the document for those interested

Are Nitrogen Molecules Really Larger Than Oxygen Molecules?
The correct answer, with respect to “permeation”, is yes.
Graham’s Law Explained:
The Difference between Effusion and Permeation
There's often confusion associated with the molecular size, molecular weight and permeation properties of
oxygen and nitrogen molecules, and GNI is often called to task to explain why nitrogen actually migrates
(permeates) out through the rubber of a tire slower than does oxygen. We felt it best to leave it to the expertise
of Dr. Keith Murphy to elaborate on the scientific principles:
"Effusion" calculations are not appropriate for "permeation" of gas molecules through materials, such as the rubber of
tire walls. There is a fundamental difference in transport occurring through “effusion”, and transport occurring through
“permeation”.
Effusion would be appropriate, if the O2 and N2 molecules were passing through a relatively large passage way
through the tire wall, such as a leak. Graham's Law for "effusion" applies ONLY if the exit through which the molecules
pass is relatively large compared to the size of the molecules and does NOT obstruct or constrain one molecule from
passing through relative to the other molecule. O2 and N2 molecules are only slightly different in molecular size but
both are very small. Thus, to constrain one molecule's (e.g., molecule of type A) passage relative to the other's (e.g.,
molecule of type B) passage, that passage way size must be fairly close in dimension to the sizes of the molecules
themselves.
Graham's Law does not apply, if the passage way is very small, as occurs for dimensions of passage ways in-between
the polymer chains in a solid rubber, where the dimensions between the polymer chains do indeed constrain passage
of the larger size molecule, which is actually N2, compared to less constraint on the smaller size molecule, which is
actually O2.
It is often mistakenly assumed that "molecular size" correlates directly with "molecular weight". O2 does have a greater
molecular weight (32) than N2 (2, but O2 is actually smaller in size. Thus, O2 fits through the relatively tight passage
ways between polymer chains in the rubber more easily than does N2. The difference is size between O2 and N2 is
very small, only about 0.3 times 10 to the -10th meters (0.00000000003 meters).
....................

[blutopless2]

And those things matter if you're filling a race car or aircraft tyre where you want 100% consistence and cost is not an issue.

i agree. ...........

[G-rig]

How much does the ambient/outisde temperature affect the pressure range anyway? The PSI wouldn't vary that much really would it?

[Maverick]

How much does the ambient/outisde temperature affect the pressure range anyway? The PSI wouldn't vary that much really would it?

See my post on the previous page.

[passatpout]

I won't run anything but nitrogen in Canberra. One of the biggest temperature ranges in Australia. Down to -10 in winter (or colder) and over 40 in summer. The reason planes have only used nitrogen for decades is mostly because its volume barely changes based on temperature compared with air. Means pressures are more consistant across all temperature ranges. And that's really the only benefit - more consistant pressures regardless of temperature.

The reason planes use it is because nitrogen is less likely to support combustion if the tyre pops or explodes. An extreme example - early US spacecraft (Mercury, Gemini and Apollo) used pure oxygen for the atmosphere, which contributed to the fire in Apollo 1. Russian craft used air, partly on the basis that the nitrogen can reduce the spread of fire through the oxygen not saturating all the fuel.