Why Use CO2 Instead of Air?
 

So, when inflating my tire today using a CO2 cartridge, I thought about why we compress CO2 instead of plain old air. Any ideas? I would think--with my complete lack of knowledge about anything--that air would be cheaper and more plentiful to bottle up than CO2.

Faster when repairing a flat during a ride. I use a floor pump at home.

Your Co2 filled tire will probably need re-inflated in a couple of days.

does the c02 have any effect on how long the tire may last? just a random thought...

Wow, you both completely missed the point of the question...

I think the other responders have mis-read your question. I don't know the real answer, but perhaps the molecular structure of CO2 allows more gas to be compressed into the space of the cartridge than plain air, which is mostly Nitrogen (I think), then Oxygen, then minute amounts of other gases, including CO2. If more gas can be contained in a smaller space, then you've gained some efficiency in packaging. Just my theory, have no idea whether it's accurate.

This is about paintball, but basically answers the question.

Probably not. CO2 is relatively inert.

I can't answer the OP's question (is CO2 easier to bottle than air), but do agree with post #3... CO2 molecules are smaller than the N2 molecules that comprise 78% of "regular air", so they leak out of your tube quicker.

Bonus: Since most of what leaks out of a tube aired up with a regular pump is O2 and other small gases, over time you should have a tube containing almost completely nitrogen, which should stay at the desired pressure for longer.

water in compressed air is annoying.

I was going to respond on this thread, but I won't. From what I have seen in the past it is better not to start giving out scientific or engineering analysis on BF. It can lead to really stupid pissing matches.

Is it really?

My compressor in the garage has a little filter basin that I have to occasionally empty as it fills up with water that I can only assume comes from the air (O2) it is compressing. When I go to use the compressor, no water comes out of the nozzle.

I really don't know the answer, I'm just playing devil's (mild) advocate.

priceless

I asked this same question to some guy at Geniune Innovations and he told me that Co2 can be compressed more. If they used air, the cartridges would be bigger. He also told me that a person would exhale more Co2 pumping up a tire by hand than a Co2 cartridge holds. Not sure if this is true and I have no way of testing it.

Reading that, it seems that the problem with compressed air is that it needs a regulator to control the flow. But that begs the question, do you need to regulate the air flow for filling up a bike tire?

That would make sense as to why they would prefer Co2

I read that as they needed a regulator to control the flow when filling the tank, not when using it. Maybe its not relevant... that's what I get for a 5 second google search. :p

Mollusk has already warned me against this, but anyway...


...most of the water will reach a condensation pressure when the air is compressed, but not all of it. Some of it is still in vapor form when it comes out of the compressor nozzle.

http://www.blurtit.com/q988089.html
taking this as fact (scary on the internet)
Say it takes you 1 minutes to pump up your tire. Then you breath out 0.08 liters of CO2 in that time. 1 mol of gas at STP is 22.4L, so we're assuming 0.0035 mol of CO2. Molar mass is 12+32 = 44 g/mol of CO2 (roughly).

This gives us 0.154 g of CO2 pumping a tire. Now, lets assume you have an inefficient pump and you're breathing hard, It may take twice as long and you could be breathing 5 times as hard. Still only 1.5 g of CO2. Standard cartridge is 16g.

also, mollusk wins.

:roflmao:

And that's what I get for reading too quickly.

Note that I never actually stated anything as fact. I made it clear that I did not know the answer.

Interesting, and it makes sense. Plus, it answers the OP's question. :thumb:

I don't tend to believe people that write things like "Liquid CO2 can also occasionally enter into the gun, causing mechanical problems and breaking paint in the chamber." Since you need about 700 psi to get CO2 into a liquid at room temp.

:roflmao2::roflmao2::roflmao2::roflmao2::roflmao2::roflmao2::roflmao2:

Here are my answers....

Campy is better.

Flip it.

Pedal Hard.

Its probably simply that compressed CO2 has been coming in small cylinders for 30+ years and is readily available since there is already a manufacturing infrastructure in place because of pellet guns to paintball guns. I do not believe anyone has tried to start up a small compressed air market.

Maybe a $ million idea.