What about Helium? Would that make for a lighter ride?

Yeah but the temps on their tires are like 100 celsius+.

Helium is rare, non-renewable and the supply will gradually decrease and almost no helium will be available commercially within decades or up to a century or so, it is predicted.

Argon stays in the atmosphere and is also pretty common (More than 0.9% of the air is argon).

Hmm... good point. I think you want the measurement criteria of pressure per weight. So compare the partial vapour-pressure of argon and its weight vs. CO2 vs. ambient air. The water-vapour in air can allow you to reduce the amount and weight needed tremendously if you keep it at 100-C and above.. ;)

I can be as flip as the next guy, but this is "thread crapping", pure and stinky. If the topic doesn't interest you, then post elsewhere.

As I recall, the issue with increased diffusion of some gases had to do with the solubility of those gases in the case material (rubber). And from my chemistry, I recall that solubility is generally determined by the shapes and local charges of the molecules. Since argon is chemically inert, it essentially has no shape or local charges, so it is effectively insoluble.

Doesn't mean that it won't diffuse through the structure, or leak. But I bet it would do so at a slower rate than other gases (except krypton, xenon, or radon ;) ).

Yes, that is what I thought as well, and what I had in mind when I posted. However, my knowledge of chemistry is limited, so I wanted more opinions. :)

Do you try and ride through Strawberry Fields Forever ?

I think there are two issues here, for the technically inclined. First, how soluble is a gas in rubber tires? Second, how fast do the gas molecules move through the rubber once it is taken up in the rubber -- that is, what is its diffusivity? These are both functions of the gas's and the polymer's (in this case, rubber) chemical composition, as DMF pointed out, but are fundamentally two different properties. When these two factors are combined, engineers refer to the overall permeability, which is the mass flux (of the gas through the rubber in this case) per unit area per unit time, normalized according to the pressure drop across the rubber.

I did some google searching, and found a paper: Barrer, R.M. "Permeation, diffusion, and solution of gases in organic polymers." Trans. Farad. Soc. 35 628. It shows that the permeability of argon -- and thus how fast it will leave through the tire rubber, given the same pressure, tire thickness, etc. -- is about three times that of nitrogen. The units for this permeability look a bit goofy, but just take note that the outflow rate would be measured in "moles" or number of molecules, because it is this that determines pressure in the tire.

Some of the replies to this post indicated it might be a waste of time. Don't worry, OP, I think it's an okay question! In fact, I can remember an exam question some time ago regarding patents that Air Products, Inc., (in Allentown, Pa.) had filed for a gas that could be used to pressurize tennis balls. They claimed that the gas increased the usable life of the tennis balls by a factor of two or something like that. I guess I would argue that questions like these, then, can be fruitful/significant!

[EDIT: The tennis ball invention is US Patent 4,358,111.]

We're talking about butyl tubes though, not rubber tires.

Busted again. I'll have to find another thread to recycle methane in. :rolleyes:

I was too precise. The moisture causes the expansion. Been there, done that.

Both organic polymers. ;)

To heck with theory. Got an argon tank? Air/argon up a couple tires and let them leak down. Then reverse them.

Plot the pressure decrease over time. Then we can puzzle about the results. In this wise are theories born (and buried).

Don't make me post the [Global Warming == Cow Farts] picture! http://www.thesmilies.com/smilies/su.../wide-eyed.gif

Nope. http://www.bikeforums.net/images/smilies/biggrin.gif

Easily over $200 for a normal size tank, and about $25-$30 to fill it. I have an argon/C02 welding tank, on my welder of course, lol.,,,,BD

The difference is tennis balls don't have valves and can't be repressururized so reducing pressure decay is a big issue.

Bike tubes can be refilled as often as you need to, including daily for high-pressure track tires with latex tubes.

Helium.

Lots of Helium.

Edit: Just realized this was already suggested.
Well, comparing these gases to the currently used fresh air, all of these are unreasonable as they are not practical. A simple pump of air is. The benefit weight wise of any other gas is probably not worth the trouble.

The question was theoretical - I'm not likely to go start trying to fill my tires with helium and if I where it would not likely be on a regular basis due to the cost of air (free) versus helium (not free). Given the theoretical nature of the question - renew-ability is moot point.

True, good point. I think air is indeed the best thing for bicycle tires, and my point was that argon would seep out faster than air through tubes, probably due to its smaller size. I was just pointing out that the OP's question wasn't totally out there.

I figure the weight savings would be about 8 g per tire for 27"x1" tires at 100 psig. As was pointed out, however, helium is becoming more scarce, so don't tell the WWs....

Helium, though normally uncharged and non-reactive, is one of the most difficult gases to contain. You'd have to refill your tires more often than with regular air, or nitrogen, or argon even, possibly during the course of a longer ride.
I'm sure the He tire fill's been tried by racers; I don't think it would be such a hot idea though.
I think there was something like this on another thread.

:D

This thread is toast...

I would argue that methane is even more difficult to contain, especially when one's finger is pulled.