Nitrogen filled M/C tyres?

[Mikkel]

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

Why yes indeed they do. Now what - simple - geometric shapes are available if you connect to particles? Just one... O=O/N=N (O2 is a double bond and I believe N2 a triple bond).
Looking along two axes these will have that shape - but looking along the longitudinal axis they'll look like O and N.

Thus, it matters how tightly bound the electrons are to both atoms in the molecule in all of the three dimensions.

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

Nitrogen = 1.55 Angstroms
Oxygen = 1.52 Angstroms

I assume that these are for the un-bound atoms - not when hooked up in an N2 or O2 molecule. But I am being unreasonable - calculating the precise spatial distribution of the electron cloud for a molecule (even a simple one like O2 and N2) is not trivial. See Wikipedia on Orbital hybridisation for more detail, that's the way to precisely calculate the spatial shape of a molecule.

All I am saying is that you can not argue that only the bond length for the molecule dictates its dynamical cross-section. It's a gross simplification. A wise man once said "Make everything as simple as possible, but not simpler."
Alas, this physical chemistry is not really that simple.

[3umph]

[Mikkel]

Yes, sorry here I'm getting all carried away again

Can't help it - and it seems I will never learn

[3umph]

Yes, sorry here I'm getting all carried away again

Can't help it - and it seems I will never learn

looks like you have learnt too much...

[Forest]

I found a fairly definitive answer to this and it appears that I was wrong.

Modern tyres are lined with a coating of polyisobutylene which provides resistance against gas diffusion from within the tyre.

It appears that polyisobutylene is more effective at containing Nitrogen than oxygen and other gases. So a 100% nitrogen filled tyre will in fact go flat at a slighter lower rate than an air filled tyre will.

You can read more about this at the following link:

http://www.composite-agency.com/mess...n_in_tyres.pdf

[SARGE]

the big question is... for Joe public like me is there any advantage/dis advantage to using the nitrogen or world we not notice any difference??

my guess is that no difference would be noted by joe public

ok ok ok.. i admit it.. i have filled both my bikes up with Nitrogen...


couple reasons..

i have 2 big street bikes .. i dont commute on them.. work truck takes care of the morning drive.. i only ride once every couple weeks ..Nitrogen keeps a steady pressure so i dont have to worry about it .. wish i could do that with a battery...


second.. normal compressor air is wet.. water is heavy.. nitrogen fills tend to give you a lighter, drier fill.. reducing weight of your wheels. Gyroscopic weight therefore is reduced..its not a set of new hi end carbon wheels but its a start... i'd love to fill my hoops with air thats been put through driers and filters but thats not gonna happen at Firestone or frank Allen or the local servo

THE QUESTION IS, WHERE'S THE WEIGHT?

REDUCING THE WEIGHT OF YOUR WHEELS IS THE MOST IMPORTANT PERFORMANCE CHANGE THAT YOU CAN MAKE TO YOU MOTORCYCLE!

Lighter wheels will make a major difference in the handling of your bike. They will also greatly improve the acceleration and deceleration "braking" of your bike for the following reasons.

Static Weight: Each ounce of reduction of the wheels weight is equivalent to 4 ounces on the sprung part of the bike. Magnesium wheels will normally weigh at least 10 pounds less than your stock aluminum wheels. This is equal to 40 pounds of weight reduction on the bike. That's alot of carbon and titanium.

Dynamic Weight: This is the weight reduction on the rim of the wheel and this is where the ACTION is. EACH OUNCE OF WEIGHT REDUCTION ON THE RIM IS EQUAL TO ABOUT 25 POUNDS OF WEIGHT AT 100 MPH!

This is real weight that must be turned, accelerated, and stopped. As an example, a pair of magnesium wheels will normally reduce the total rim weight of the two wheels by at least 20 ounces. This means that your bike will weigh 500 pounds less at 100 MPH.

At all other speeds the reduction is in relation to the velocity of the bike. As you increase your speed the weight will increase exponentially.

The following formula will enable you to figure for yourself the impact of dynamic weight on your bike.

Given:
V=Speed of your bike in MPH.
D=Diameter, outside of tire in inches.
G=G Force (Times force of gravity)

So: 1 oz. At the surface of the tire at 100 MPH produces a force of 600.37
ounces, or 37.52 pounds.

Force at the rim: Let's say the rim is 2/3 the way from the axle to the surface of the tire. This equates to 17 inches for the wheel and 10 inches total for the tire. To arrive at the percentage, divide 17 by 27 which will give you 63% which is the distance of the rim from the axle in relation to the overall diameter of the wheel and tire.

Multiply the force at the surface by 63%. 1 ounce on the rim is about 23.64 pounds.

REMEMBER! THE MOST IMORTANT PERFORMANCE ADVANTAGE THAT YOU CAN GIVE YOUR BIKE IS LIGHTER WHEELS!

just my opinion ..

[SARGE]

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.