What Exactly Are CO2 Cartridges?CO2 cartridges are small metal containers, about the size of your thumb, that hold highly pressurized CO2 (carbon dioxide) gas. Though they have a variety of uses, cyclists carry them along with an adapter for use in reinflating tires that have gone flat out on a ride.
Why Are They Useful?CO2 cartridges are popular because, in the hands of someone who knows how to use them, they quickly and easily inflate a tire that has gone flat. Literally in a matter of seconds. And in the case of road bike tires, CO2 cartridges provide inflation to the high PSI air pressure that can be difficult to achieve with many frame pumps.
How CO2 Cartridges WorkCO2 cartridges typically all work the same. The user takes some sort of inflator/adaptor head which screws down onto the cartridge and seals itself on the cartridge as it breaks the seal on the container. By placing the inflator head on the valve of the bike tire, the cyclist can then -- by either twisting or pushing down on the inflator head -- transfer the highly pressurized CO2 from the container into the tire, causing it to rapidly inflate.
What Are The Drawbacks?
CO2 cartridges are nifty. They are light and simple to use. New users however can find it difficult to gauge exactly how much pressure the CO2 cartridges are delivering. Many cyclists have blown out tubes by over-inflating them, but that gets easier with practice.
Also, the CO2 cartridges are generally for single use, so if you've got a delicate conscience about the environment, it might bother you to cast aside the metal containers each time you inflate a tire, though recycling is an option.
And finally, carrying CO2 to save weight is usually a fallacy as most cyclists I know still carry a frame pump "just in case."