One of the things I have heard is that if you inflate with CO2- then the following day pressure will be down. I have just replaced the tyres on my Ultegra wheels that have not been used for a month. These are normally used at a pressure of 140psi and when I took them off the wall- The pressure was still rock hard. Co2 and the pressure would have decreased.
I am a firm believer in a Pump to inflate but It does take effort and does take time. I still would not trust CO2 as I have often come across riders where the inflator has not worked and loaned them my pump. I have also come across riders where their pump has not worked either so Take your choice.
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How long was I in the army? Five foot seven.
Spike Milligan