CO2 cartridge question

12g will get a 700c tire 90 to 100psi if you get it all in there. I just use 16g ones, gives you some error room. www.biketiresdirect.com usually have no-name threaded ones at good prices.

I just tested a 16gm C02 cartridge on a 700x23c tire.  I measured the pressure afterwards and it was 120.  There was a little hiss around the side as it pressured up, so potentially it could have been a little higher.

I weigh 200lbs and tend to bias my weight to the rear so I need as much pressure as the tire can hold.

A 12 g will be more than enough for a 700 tire. A 16 will give you one and then some. You really don't need 110 psi, just enough to ride on. Two 16s will get you through 3 flats, if you happen to be unlucky enough to have that happen to you. :p

I bought a case of 12oz cause they were cheap and I have a pellet gun. I found they barely got the tire to 75 which will be ridable but pinch flats galore. There is no good reason not to carry 16s instead (which I also found only to get about 110 with a full cart).

...Unless you're riding on 650s like me.  12s are perfect for them.