R36 - Nitrogen

[apom]

Maybe it was Helium instead of Nitrogen thus making the downforce on the road less and therefore reducing the drag and hence better fuel economy!

[Maverick]

A few more links

Nitrogen in car tyres latest evidence that marketers believe a fool is born every minute

Snake oil in your tyres

Is it better to fill your tires with nitrogen instead of air?

Fill 'er Up - - With Nitrogen

Should I use nitrogen in my car tires?

And I can't remember where I found this but may be of interest.

"Putting N2 in tyres has more to do with that you can charge lots of $$$ for N2, but not for air.

N2, being a smaller molecule, diffuses out faster. Having less weight, it also improves handling as there is less rotating mass - but not by much. If we assume a tyre has a volume of about 24 litres and is at 2.5 atmospheres pressure, then the weight of dry air in it will be 72.5 grams. (with air at 80% relative hummidity, it will be about 71 g). Fill it with N2, and it will weigh 70 grams. So you save a whopping 2.5 grams out of maybe a total tyre weight of 10 kg. Olympic cyclists fill their tyres with He to save a few grams - but then a few grams means 0.01 second which might be the difference between a medal or not.

A gram or so of ice in the tyre may cause issues, providing you drive around corners at 300 km an hour within a few seconds of starting the car and before it has melted and evaporated.

As the tyre warms up, the air or nitrogen will expand. If the tyre is at 20 C and then warms up to 40 C, then the air or nitrogen will expand by 1-((273+(40-20))/273) = 0.07 or 7%. If the tyre is at 35 psi at 20 C, it will increase to 37.5 psi at 40 C. Filling with different gases will make no difference as they all expand the same amount if raised by the same amount. If anything, using a denser gas such as S8F will take longer to heat up due to the higher specific heat (amount of heat required) to take it from 20 to 40 C (or whatever) but then will stay warmer longer."

[G-rig]

One of the guys at Bob Jane today were mentioning Nitrogen when I went in for a rotate & alignment, and it didnt take me long to say 'Normal air is fine' and they didn't even mention the price.

They claimed you don't need to check your tyres for 6 months, but it's pretty easy to see it's just a money making idea.

[richdave]

Nitrogen charging of tyres....


God's way of saying you have money to burn

[richdave]

N2, being a smaller molecule, diffuses out faster. Having less weight....

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

[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.