Tire Question !

[kestrel74]

If I fill my tires with Helium.................will it make the car lighter ?........................................

hmmmmmm

( sorry, I havent driven it in almost 24 hours and I'm getting a little crazy )

[cerven]

Probably so - Tire Discounters here has exclusive (for around here at lease) NITROGEN INFLATION which is WAY better that air for hundreds of reasons (I just can't remember any of them at the moment) I think that possibly FLATULENCE INFLATION may have some advantages but I haven't thought that out fully yet.

[NMRJock]

Nitrogen does have some advantages if it is dry nitrogen. Helium would have the same advantage. But weight isn't it. The weight difference between the tire filled with compressed air and the tire filled with compressed He is negligible. The nice thing about using a dry gas is that without moisture the pressures change much less with temperature. That is why the F1 guys do it.

[Racer X]

Originally Posted by kestrel74

If I fill my tires with Helium.................will it make the car lighter ?........................................

hmmmmmm

( sorry, I havent driven it in almost 24 hours and I'm getting a little crazy )

Yes, it will be lighter.

But I am not sure it make it quicker as a result. That's because it's not low weight that is important, but low mass. This is an example that weight and mass are not equivilent, it is just hard to really measure mass in the normal world without special tools or calculation. I am sure one of our engineers can tell us the mass differential between air and helium in tires of our volume. And does the mas of the gas in our tires impcat rotational weight the same way because of it's fluid nature.

Also, I think you would have to "air" them up more frequently as the tire may be more permiable to helium than air. I am sure this has been tried before.

Greg

[kestrel74]

I was actually thinking about changing to Nitrogen ( as i have a readily available source, being in the aviation business )

uhh..... the Helium thing was just a joke...... " dry " ( gas ) humor ??

[ConeFusion]

Nitrogen works just fine. I believe it's used for some aircraft tires. Remember that air is about 78% nitrogen, so it's not that different from using air. The main benefit of using pure nitrogen is that you don't have any moisture in it.

Helium doesn't work. It would pass through the rubber, and the tire would deflate quickly.

[EdHahn]

A "serious" answer:

1) Recall that pressure, volume, and temperature for a gas are expressed as PV = nRT, where n = the number of moles (a quantity of molecules), and R is a constant (the gas constant). Therefore, one can see that, for the same pressure, volume, and temperature, the number of moles (quantity of molecules) will be the same.

Since the quantity is the same, with helium inflation you end up with a volume of gas that has molecules of atomic weight 4, vs. the average for air of about 14.5 (given the same tire size, inflation pressure, and temperature). So, a tire filled with helium will have a little over 1/3 the gas mass of a tire filled with air.

Since the mass of the gas is pretty small, the effect is pretty small - but it is real.

2) The problem is the size of the molecule - since helium is a single atom molecule, it is much, much smaller than a molecule of nitrogen or oxygen. Therefore, it will leak down very quickly compared to a tire filled with air. (This is why rubber balloons go flat sooner with helium fill vs. air fill.)

3) Dry nitrogen fill is beneficial, as it contains less water vapor than compressed air (without a drier). Water vapor can cause unpredictable changes in tire pressure.

4) Aircraft use nitrogen fill to prevent oxidation of the tire material, leading to fewer blowouts on landing. That isn't likely a failure mode of the typical Elise tire, though.

(Hey, I have to exercise all that stuff I would otherwise forget once in a while.)

ed

[sleepless]

a problem for most of us is getting the tires mounted using a completely dry system. even if you use dry nitrogen, you need to make sure the tires weren't mounted using a lub that adds any water to the inside of the tire!

[del105]

Originally Posted by sleepless

a problem for most of us is getting the tires mounted using a completely dry system. even if you use dry nitrogen, you need to make sure the tires weren't mounted using a lub that adds any water to the inside of the tire!

The make dry tire lube, don't know what its called though.

[del105]

I just called the shop they said they use talcum powder or corn starch but they use it on bike tires and he isn't sure if it wouldwork on a car tire.