Originally Posted by professorbob

I didn't read all the responses, so forgive me if this was covered. I've noticed that if I use a CO2 cartridge, the tire will be a little soft the next day, whereas if I use a hand pump, it stays hard. It makes me wonder if CO2 molecules penetrate the pores of the tire easier than air, which is mostly nitrogen. I also notice that some automobile tire dealers use nitrogen. In any case, I have both but always end up using the hand pump.