When a co2 pump cartridge description says "will fill a tire to capacity" what 'capacity' is that? I am currently riding mtb tires at 65ish psi, but im looking to replace those with Geax Evolution or something similar. I commute to work on a bit of a tight schedule so id like to get a co2 pump but I don't know how much Co2 a cartridge will hold.

I use Crosman 12 gram cartridges, it takes 2 to fill up my 100 psi tires. So figure 1, 12 gram cartridge will fill up appx. 50 psi. I am too cheap to buy the cartridges sold at bike shops. I buy mine at Wal-Mart.

CO2 cartridges are only for temporary filling of the tire. The CO2 will diffuse through the inttertube and even if the tire is inflated to a good pressure with the cartridge, the next day the tire will need more air.

Ill keep that in mind. I have a Trek mini pump that does pretty well, but it takes awhile to get up to pressure on my tires. I just wanted to have a failsafe in the bag.

So, thumb rule of CO2 is to use, then deflate when you get home and refill?

I wouldn't deflate and refill. The "leakage" issue is not that severe. You might find that a 16-gram cartridge can get your MTB tires up to 40psi or so in one shot. Thy're a lot more expensive, though...

They are great as a tire repair. Don't have to spent the time and energy pumping up the tire. You can use that riding.

And as an addition, you don't have to do all that pumping with a tiiny pump on the valve. I can't say how many Presta valves I've broken as a result..

That's when something like the Road Morph is a nice idea since they use a short section of hose.

For commuting purposes, I prefer Co2 carts as time is of the essence. Pop off the wheel, peel off the tire, replace the tube/tire, hit it with two Co2 cartridges, replace wheel and ride off. I'll patch the tube when it's convenient and I top off my air pressure each morning so I don't worry about Co2/air loss.

Did some hunting, and found this stuff. Obviously, the pressure you get depends on the tire you are filling.

12 gm cartridge tire Tire inflation capacities:

700x23 - 94 PSI
700x25 - 90 PSI
650x20 - 125 PSI
650x23 - 110 PSI

16 gm cartridge Tire inflation capacities:

700x23-130 PSI
700x25-120 PSI
650x20- 180 PSI
650x23-170 PSI

"A 16-gram cartridge will put about 40 psi in a mountain bike tire and about 125 psi in a standard road tire. "

Google is your friend.

I'll get my riding in during the time I don't have to be in Wal-Mart or the bike shop buying more CO2. And since the greatest amount of time I spend changing a flat is finding what caused it so my new tube doesn't immediately deflate, it's not costing me a lot of time on my commute. My Road Morph will fill my road bike tires (700x23) in a matter of a couple of minutes.

My commuter has a Road Morph. My fun road bike has CO2. Priorities I guess. I don't care about how the commuter looks so much. I don't like a bunch of crap hanging off my road bike. I carry two 16g cartridges. One will fill the tire.

That is why you always check your tire pressure every time before you ride and air them up to the max pressure.

This is an aside, maybe it might apply to some of you commuting on mountain tires.

Many mountain bikers run Stans Sealant in their tires for sealing of tubeless tires, automatic sealing of pinch flats, thorn punctures, etc. (roadies don't use Stans because it does not work at the higher tire pressures). Also you can buy "slime tubes" that have the sealant already added.

Turns out that CO2 causes the sealant to congeal into a rubbery lump. One of my buddies recently used a CO2 cartridge to inflate a new tires he had just mounted up and poured a capful of stans into. He spun the tire and we could not figure out what that noise was as the tire rotated. We dismounted the tire and a clump a grey, congealed Stans fell out...

I use CO2 on the commute IN to work, because I'm riding to catch a train, and I'll be waiting for 35 minutes if I miss it. Going home, I use the Road Morph, and save my CO2.

All my MTB buddies use CO2 and Stans or other tubeless goo. I know Stan's dries up over time, but I've never heard of it being instantly congealed by CO2.

I just don't see the CO2 being that much faster. I used to bring a couple of CO2 cartridges and their delivery system/valve but I realized that the volume was actually about the same as the road morph (albeit easier to pack because it's broken up into pieces), and the weight's within 100 grams or so.

I do tend to flub the CO2 seal too. The pumping itself probably adds about 2 minutes over the cartridges, some of which is recouped by the fact I don't have to assemble the cartridges.

I just carry the pump in the (messenger) bag as I have to lock the bike up outside anyway and I don't want to leave it on there.