Man, I've been trying to answer this since last week. The Beta version has some major bugs, but as of now, I'm able to finally log in thanks to the efforts of your tech people.

I used to use a frame pump but switched to a CO2 inflator a couple of years ago. Lots easier to use, takes up a less room, and let's you get more air into the tube. I use the smaller size cartridges, think they are 12 oz., once you put one into the inflator and break the seal, then you have effectively used it up. Anything that was left will leak out over a couple of weeks. Hopefully you aren't flatting out that often. I keep an inflator, two new cartridges, a patch kit, and a new tube in a plastic baggie inside my seat bag. Also have a little took kit with two tire levers.

As for a "How To": Break seal and take the tire off the rim on one side, tire levers come in very handy for this but have seen it done by hand. Remove tube. Check inside of tire, no use putting a new tube in if there is a piece of glass or something still poking through the tire. Patch tube or put in a new one. Blow into tube to get a little air into it. Put tire back on rim, careful you get tube inside the tire all the way around. Put on inflator and squeeze handle for a short burst to seat the tire to the rim. Deflate then reinflate until tire feels really hard. That will pretty much take whatever is in the cartridge, I've never blown out a tube using a 12 oz. cartridge. You will come to a point of equilibrium where the pressure in the tire is equal to the pressure left in the cartridge so I don't think its that easy to blow up a 700c racing tire past 100 lbs psi. Top it off with a floor pump before you go out on the next ride. Replace the CO2 with air? Why would you do that? I have no idea if it would deflate quicker, but I check my tires at least once a week anyway. CO2 is not lighter than air, it's heavier.

Just a couple of further thoughts on CO2 pumps-

I carry one of the slightly larger ones that allow hand pumping as well as cartridges for those really bad days when you run through both CO2's. Its helped me twice on long rides especially in the NYC Century, with glass, potholes, grates and curb jumping all part of the adventure.

On replacing CO@ in a tube- two of my ride buddies use thin or latex tubes and the bottled air really does not last as long, as little as a day. I top off every ride so I mask the effect if it shows in my tubes at all. I use slightly tougher Specialized tubes, the semi threadless ones so I can get a floor pump head on and off easier. But I think the leakage theory using CO2 is real.

One thing on spare tubes- I open mine up and test inflate them so I can coat them with baby powder. I make the flat fix faster and less chance of a pinch flat reinstalling the tube.

Hope this helps!

I switched to CO2 about 10 years ago, and love it. I do tend to ride in groups, so what I do may not apply to those who ride alone most of the time. I carry 2-3 small cartridges, and an inflator that has a trigger. the triggerless ones are tougher to control. I also carry a spare tube when i'm riding clinchers, and I always carry a $20 bill, to either use as a tire patch (from the inside) or for cab fare when things just aren't going my way. using CO2 is much faster than pumping, which is important when riding with others. I figure, if 2-3 cartridges doesn't get it done, I give up....it's just not my day....or i can always rely upon the kindness of strangers, which is easier here in southern california where cyclists are everywhere.

Plenty of good advice so far. I have a slightly different view of a couple of things. So far I haven't heard any empirical evidence that the CO2 dissipates through faster and I'm inclined to think not, The molecule is heavier (one carbon, two oxygens vs. two oxygens) and probably is a bigger molecule as well. If someone has a CO2 cartridge to spare, pump up a tire with it. Check the pressure and then put the identical pressure in the other tube with a similar tire using your floor pump. Check the pressure after a couple of days. There's your test. Check your pressure daily anyway. I would not count on any residual CO2 lasting "weeks" and not even days. Consider it empty. I use the 16 gm cart's myself as my tires pump up to 145 and going too high has never been an issue. The downside is that you can usually buy threadless 12 grammers for a bigger savings at say a KMart instead of at a bike store. I've heard they make them for guns too (and I don't care to know about this actually) but there could be an oil in some. Avoid that. I use a little valve type system that is spring loaded. If you have one of those it is a lot easier if you retain the nut and secure the valve onto the rim so it doesn't push into the tire when you put the upward pressure on the valve inserting the CO2. Also be alert to the fact that some valves are smooth and not threaded so don't get those if you use a spring loaded valve type inflator.

Carrying money is always a good idea but using money to patch a tire is silly now as every saddle bag should carry a "tire boot." For $3.00, or so, you can buy a pack of PARK tire boots which includes three tire patches. They have an adhesive on one side of a heavy plastic credit card sized patch. If your tire is cut even slightly then put one of these inside the tire before replacing the tube and it will get you home without having to call someone in the family for a lift and you won't lose points that way. I guess carrying a cell phone just makes sense these days. If you bend a rim your $20 would still work for the cab and both the boot and cash weigh little so why not? I've used two boots this season but not on my wheels but I was the hero to two different guys. One on a night ride who was really pushing his luck on some very old mountain tires. We were dirt road riding and about seven miles from the car but it was already after 11pm so it would have resulted in one of the other guys picking him up and costing both about an hour of sleep that night. The other was a fellow on a brand new Continental 4000 rear tire that only hit some gritty stones and put a small hole in the tire right on the riding surface near the start of what turned into a 40 miler. He completed the hole ride but usually if a tire requires a boot, its toast. By the way, that happened after a rainfall so the roads were still wet. I always make sure to clean my tires off after riding through grit in corners with my gloved hand. If you aren't comfortable doing this while riding, stop and do it that way. To do it while riding I'll open handed 'palm' the front tire to remove any residual grit. Certainly, if I think I might have been near glass I'll do this as well. A good reason to wear gloves. Then for the rear it is a tad trickier. Don't do this unless you are confident or have someone teach you. Open your hand, and put the back of your hand on the seat tube then push backwards a bit till your palm hits the tire. Let it glide there a moment then pull your hand back to the seat tube and then out. The 'push/pull' dynamic will minimize your risk of hurting your fingers. I wouldn't do it at all in a race under higher speeds to maintain control. I suppose the best way to repair a flat is to decrease the risk of getting one in the first place. Of course, carry extra tubes and more than one cartridge. I often carry a very small pump that fit in my relatively small saddle bag as well. Work force has one I've used and gotten over 90 lbs of pressure in and Topeak makes an even smaller one that goes high as well. Ask around. There are some neat small pumps available.