On my Tarmac - which is my training, sprinting & climbing bike I carry CO2, I have a simple device that threads onto the cartrage and you just back it off a bit to let it fill the tire. I give it the whole load. I carry 2 cartrages. On my Simoncini - my distance bike I have a road morph pump, I can also carry CO2 as I have an extra head but don't any more. On the commuter which has low pressure MTB tires, just an el-cheapo pump. The only time CO2 has let me down was on my first race last weekend where I flatted twice and because I had no pump - I was done.