I agree with operator. Plus, with CO2 you always have to be buying the cartridges. Air is free. It's been my experience that you only get one fill out of a cartridge - even if it doesn't take all of it to fill the tire, by the time you need it again the cartridge has leaked empty and you need to use a fresh one. And too, you are producing more waste with CO2. (By the way, those of you who do use CO2, did you know the empty cartridges are recyclable - at lest in some places? Just toss them in with your pop cans.)

And if you haven't already tossed out your old frame pump, check with the manufacturer to see if you can get a rebuild kit for it. I did this a couple of years ago for my Blackburn Shorty mountain pump - they sent me a rebuild kit free for the asking.