Gas in tires

[Jersey Tom]

Now, if you were really serious about keeping pressure constant, why on earth wouldn't you use a polymer to cover the inside of the tire, a polymer with a pore diameter small enough to contain the gas inside?

I dare to guess that's what the tire makers do.

I don't see how that would keep pressure constant.. unless you mean preventing it from leaking, not from building up with heat.

[tc9604]

I have heard about a gas containing Magnesium that has the "weird" property of not increasing its pressure when heated.

I find it hard to believe and I guess the person who told me that was not well informed at all, maybe he thinks that Gay Lussac was a famous homo writer or something.

Anyways, he also told me the gas costed 300Usd per tyre set pumped and that it was used by some top level teams in a local series here in Argentina.

Sounds interesting, but if energy is added to the tyre + gas through heating then where does it go if not into an increase in pressure? Definitely one to think about.

I'm not sure how useful it would be really, I guess it would come into its own under start or safety car conditions when you would like the tyres not to lose pressure.

[PlatinumZealot]

We can compare the properties of the HFC 404A to Carbon Dioxide, Nitrogen and Air to get some clues as to why it is used.

[Belatti]

To keep pressure constant would not be easier to put pressure relief valve?

[Ciro Pabón]

... and keep the heat increasing all the time.

[ISLAMATRON]

To keep pressure constant would not be easier to put pressure relief valve?

Because a pressure relief valve would keep constant pressure by releasing some of the tire air to the atmosphere... but then if you have to slow down such as in the case of a Safety car both the temperature and pressure go below optimal operating perameters... the pressure goes even lower because you lowered the amount of air in the tire via the pressure realease valve, thus making it even more difficult to get the tire back up to temp & pressure.

Now if they link the pressure relief valve to a remote reservoir like many shock systems do currently, and feed the air back into the tire it would work, but this increases the complexity of the system several fold, and adds to overall weight.

[Ciro Pabón]

This is a weird idea: couldn't we use the fact that the tyre flexes to "self-pump" air in?

[Belatti]

... and keep the heat increasing all the time.

No!

[Belatti]

Because a pressure relief valve would keep constant pressure by releasing some of the tire air to the atmosphere... but then if you have to slow down such as in the case of a Safety car both the temperature and pressure go below optimal operating perameters...

Yep, thats what I thought.

Thats why I have seen that in series where races are sprints with 20-30 min max and you rarely see safety cars

[Jersey Tom]

This is a weird idea: couldn't we use the fact that the tyre flexes to "self-pump" air in?

Nah.

Also, with regard to relief valves.. they are prohibited in certain series for safety concerns.

[ISLAMATRON]

This is a weird idea: couldn't we use the fact that the tyre flexes to "self-pump" air in?

actually that is quite an interesting idea... a spring loaded 1 way check valve would do the trick

[Belatti]

This is a weird idea: couldn't we use the fact that the tyre flexes to "self-pump" air in?

Nah.

Also, with regard to relief valves.. they are prohibited in certain series for safety concerns.

I see. A valve failure = a puncture ?