CO2 is not completely reliable and can be done wrong. A pump always has air as long as I have arms to pump it up. I carry a Lezyene small pump on one water bottle holder and CO2. Normally I simply use the pump it can get me to road pressure of 95[psi in about 200 strokes. I would use the co2 if in hurry but really the pump works. I carry 2 tubes no patch kit so if I have more than 2 flats I have to use my cell phone. That has not happened but I have had co2 not get seated correct and rush out or not fill just right. I have had a spare tube actually go bad and when I tried to use it it had a leak. I have had a value stem go bad on a spare tube.

To me the moral is I want air..............pump. After all for me I am not racing anywhere.