CO2 in my tires

You probably remember the ideal gas law from chemistry class, PV=nRT. If you understand this equation, then you'll realize that the heatup/cooldown of tires due to usage or environmental temperatures has no relation whatsoever to the type of gas inside your tire. Changes in pressure of a gas in an enclosed system are not affected by type of gas.

Lots of discussion out there on the exaggerated benefits of using pure N2 gas in automobile tires. Google it. Here's one good discussion: The force that through...: Nitrogen for tires?

Any touted difference in diffusion rates is unsubstantiated. N2 and O2 molecules are almost the same size, and air is 80% N2 anyway. The only plausible benefit to using pure N2 is that you might reduce the oxidation of the rubber inside the tire. But, I would think that you would wear out the tire tread long before rubber oxidation would become a problem, unless you are a car collector and wish to keep your prized possession for decades.

Personally, I have better things to waste my money on than $20 to fill up 4 tires with N2. What a scam!

As far as CO2, probably the same arguments apply. I haven't researched the diffusion rates and corrosivity of CO2, but I am skeptical. Again, the type of gas you use will have no bearing on the daily expansion and contraction of your tire. However, if you do choose to use CO2, you need to be aware that CO2 will combine with water to form carbonic acid, which is much more corrosive than the O2 within the air. Thus, you should try to use extremely dry CO2, and to displace most of the moisture (in the air originally in the tire) by filling/exhausting each tire several times.

 

No difference between N2, CO2, and plain old air. They all work equally well, assuming you get the water vapor out of them. CO2 becomes non-ideal at higher pressures and lower temperatures, but that happens well out of the range of operation for normal car tires.

Tom

 

CO2 is denser (higher MW) so you will have a slight increase in unsprung weight on each corner. I haven't tried to calculate it but expect it will be negligible.

I doubt the higher partial pressure of CO2 would have any reaction effects with the alloys or rubber. This is the area of concern I would have. Some chemists would be more qualified to evaluate the materials (including the sensors) and the combination of water, CO2, and N2. CO2 itself should not condense/freeze at these temperatures and pressures.

If there is moisture (condensate) in the tire the CO2 will more readily dissolve in it than N2 or O2 if I'm not mistaken. If this is correct then there will be more pressure loss during colder operation.

 

Are you trying to say my salesman doest know about molecules? He sounded pretty convincing. I was imaging the nitrogen molecules being as big as beach balls floating around inside my little tires, never able to escape....I'm bummed, $45.00 donation for the unwanted frills. I would have rather been sold a fox tail or baby on board sign.

 

I think the moisture question is the one that makes a difference here. It doesn't take much to get carbon dioxide to form carbonic acid in the presence of water. Of course you really need it to condense to cause much actual damage to the metals, and I think you are much more likely to see this in its preferred volatile state.

I'd prefer regular ol' air to straight nitrogen (for cost reasons), but I'd prefer either over carbon dioxide. You'd be safe if you purged the atmosphere in the tires, but why go to that effort? Put a muffler on your compressor motor or surround it with some noise-absorbing material!

 

PLUS! You've got some fire fighting ability there. Four tires filled with CO². You could go over to California and help put out fires.

Rod

 

Ferrari runs CO2 in their Formula 1 cars because it works well for maintaining the desired temperature range during the race, but they also wear out a set of tires every 20 - 30 minutes of use...

 

are you sure it's CO2, i've alwas heard of N2

 

Googling
commercial CO2 production
reveals that most of it is made as by-product of other processes, so greenhouse considerations are negligible. I would be a little worried about carbonic acid because it's hard to get all the water out of the tire, and there will be no operational benefit from using CO2, so why risk it?