Originally Posted by shimano_cranker
Listen to me...
I have the same kind of tires as you and I also have a CO2 inflator. The thing is this...16g cartriges CANNOT be bought in bulk. On the other hand, 12g cartriges can. Just go to WalMart and go to the BB gun aisle. Get a 25 pack of BB gun CO2 cartriges. This will cost you about 12 bucks. As for 16g cartriges, they run 3 bucks apiece. If you are concerned about if the 12g will fully inflate it up to 120psi, don't worry. All you have to do is carry an extra cartridge. At 50 cents apiece, it's quite a bargain. Good luck.
EDIT: Overinflating your tires will not cause much damage. There is no big difference between say 120psi and 150. The higher psi, the less chance of getting a flat because surface area of the tire hitting the road is reduced. There are no benefits over 120psi though. Just make sure the pressure is around 120psi. Hope this makes any sense at all.
Also, to efficiently pack your cartridges, place 1 in the pump itself, and then place the other ones somewhere in your pack. Once again, good luck.
A single 12 gram CO2 cartridge will put about 90 psi into your tire...enough to ride home on.
Wal Mart CO2 cartridges are alleged to contain lubricants which will harm the seals in a CO2 inflator. I don't know if this is true or not. I can't imagine why they would damage a CO2 inflator, but not a BB gun. I use Wal-Mart cartridges, figuring that the money I save will offset the cost of a new inflator.
Some inflators allow you to carry a cartridge in them. Others do not. If your inflator allows you to turn the cartridge backwards, store it that way. Don't put a cartridge in an inflator in such a way that the cartridge is punctured and expect to use it at any time in the future. Once punctured, the CO2 cartridge will leak gas, even if it is in the inflator.
Experiment with a CO2 inflator at home, before you need it. Waste a cartridge or two so you know how to use the inflator, and how much pressure you can expect from it.
I'm not crazy about the idea of overinflating tires. You may not have to be super-precise, but if you put enough pressure into a tube, it will blow out.
When I use a CO2 cartridge for a roadside repair, I always top the tire off when I get home, and add air before the next ride. CO2 may leak faster than air, but if you top off before the next ride, you'll be fine.
I always carry an inflator, a patch kit, a spare tube and two CO2 cartridges. I've never needed more than one cartridge, but the second one is insurance.