Nitrogen filled M/C tyres?

**saltydog** · 21st February 2009, 10:38

Originally Posted by 3umph

I'm amazed the banter is still going on about this...

Reckon, why not fill your bloody tyres with expanda foam.

**3umph** · 21st February 2009, 10:42

Originally Posted by saltydog

Reckon, why not fill your bloody tyres with expanda foam.

dam good question... why not... would solve the puncture issue

**Dak** · 21st February 2009, 11:10

Originally Posted by Devil

Oh god. seriously. Dont breed.

Because it has little to no discernable effect for joe bloggs, doesn't mean that it doesn't work for others, ie commercial vehicles, for which it is mainly pushed.

Little to no effect on subject X doesn't mean that it doesn't work ever.

Too much opinion and poor conclusions, too little fact.

Really, would you like me to show you the legal papers on how we are governed to sell it? Pushed for commercial vehicles? 90% of the nitrogen sales in this country are done by Fire#$%#, they will try and sell it to your grandmother. It's easy money for them, the profit margin on a bottle of nitrogen is huge.

**Squid69** · 21st February 2009, 11:11

Originally Posted by saltydog

Reckon, why not fill your bloody tyres with expanda foam.

You would need to soften your suspension.

The first stone you hit the tyre would not deform and you would probably head into the ditch, perhaps even tankslap into it...

**3umph** · 21st February 2009, 11:16

these might be better... airless tyres

http://thekneeslider.com/archives/20...orcycle-tires/

**Mikkel** · 21st February 2009, 12:07

Just before we get carried away, I'd like to point out that any gas -whether wet or dry - will expand (depeding upon the situation the volume or the pressure will rise - or both) in roughly linear proportion to the temperature.
Where wet versus dry comes into the equation is just how roughly.

Ideal gas law - this describes both nitrogen and air fairly well. At least as far as this discussion is concerned.

**Forest** · 21st February 2009, 12:10

Well let's look at molecular size then shall we.

For practical purposes, the covalent radius is 50% of the distance between identical covalently bonding nuclei.

Nitrogen's covalent radius is 75 x 10^-12 m so a nitrogen (N2) molecule is approximately 4 x 75 x 10^-12 m = 300 x 10^-12 m.

Similarly an Oxygen molecule (O2) is 4 x 10^-12 m = 292 x 10^-12 m.

So an oxygen molecule is approximately 2.7% smaller than a nitrogen molecule.

Anyone who thinks this makes a difference to tyre inflation is a moron.

**Mikkel** · 21st February 2009, 12:14

Originally Posted by Forest

For practical purposes, the covalent radius is 50% of the distance between identical covalently bonding nuclei.

Nitrogen's covalent radius is 75 x 10^-12 m so a nitrogen (N2) molecule is approximately 4 x 75 x 10^-12 m = 300 x 10^-12 m.

Similarly an Oxygen molecule (O2) is 4 x 10^-12 m = 292 x 10^-12 m.

I could be wrong, but it seems to me that there are a few numbers missing...

**Forest** · 21st February 2009, 12:18

Originally Posted by Mikkel

I could be wrong, but it seems to me that there are a few numbers missing...

Oxygen and Nitrogen are just a pair of atoms stuck together by a simple covalent bond.

The overall length of the molecule is therefore four times the corresponding covalent radii.

**Devil** · 21st February 2009, 12:53

Originally Posted by Dak

Really, would you like me to show you the legal papers on how we are governed to sell it? Pushed for commercial vehicles? 90% of the nitrogen sales in this country are done by Fire#$%#, they will try and sell it to your grandmother. It's easy money for them, the profit margin on a bottle of nitrogen is huge.

Well aware, having previously worked at the head office...
Apologies for being mildly harsh...

**Mikkel** · 21st February 2009, 13:26

Originally Posted by Forest

Oxygen and Nitrogen are just a pair of atoms stuck together by a simple covalent bond.

The overall length of the molecule is therefore four times the corresponding covalent radii.

I merely implied that your calculations, for oxygen specifically, seemed to be missing something.

Certainly, the length of the bond is important. But the effective molecular cross-section doesn't just depend upon the length of the molecule - it is after all a 3D structure.

What is most important is the radii of the electron cloud surrounding the individual atoms, in the bonded state, since this will affect the cross-section along each of the 3 dimensions.
Since I can not remember how to calculate this, and I can't be arsed reading up on it, I trust the properly referenced sources that say that nitrogen has the larger molecular cross-section.

**Forest** · 21st February 2009, 15:12

Originally Posted by Mikkel

What is most important is the radii of the electron cloud surrounding the individual atoms, in the bonded state, since this will affect the cross-section along each of the 3 dimensions.
Since I can not remember how to calculate this, and I can't be arsed reading up on it, I trust the properly referenced sources that say that nitrogen has the larger molecular cross-section.

Nitrogen and Oxygen don't float around as individual atoms at STP. They form bonded covalent molecules i.e. N2 and O2.

But to answer your question, when you're doing physical gas chemistry calculations you use the Van der Waals radius to represent the physical size of the individual atoms.

Here are the Van der Waals radii for Nitrogen and Oxygen:

Nitrogen = 1.55 Angstroms
Oxygen = 1.52 Angstroms

The difference is less than 2%.