64Paramount said:
I searched the forums and found some info on this, but nothing really definitive.
Has anyone tested maximum tire inflation PSI achieved using CO2 cartridge inflators?
I just bought a new inflator and I'm not sure how many PSI a single 16 gram cartridge is capable of on a 700x25 tire.
Has anyone tested that?
It can be calculated using ideal gas laws.
You know the mass of CO2 in the canister (16g or 0.36 moles of CO2) and the volume is given by Genuine innovations as 21cc.
It's also not hard to calculate the volume of the inflated tube (it is approximately a torus). I make it about 995cc for a 25mm tyre.
When fully inflated the tyre and canister will be at the same pressure (fluid can only move by itself when there is a pressure difference).
High school physics or chemistry gives us PV=nRT
V = volume of tyre + volume of canister = 1016 cc
n = number of moles = 0.36
R = universal ideal gas constant
T = temp = lets say 20C or 293K
gives P = 128psi
if the temp is 0C or 273K then the pressure is 118psi
So there's not much variation with temperature.
Of the original mass 15.67g ends up in the tyre and 0.33g in the canister.
This is all only accurate to within a few psi as I have assumed there are no leaks, and I'm probably within a few percent of the correct volume.
This is really as good as you are going to get as far as knowing what the pressure will be. And anyway, why would it matter? The CO2 is for an emergency fix so we don't really care how high the pressure is, as long as it is "enough".