Can you over inflate using a CO2 cartridge?
 

Calling all engineers! Yesterday I was told that by pumping in some air using a mini hand pump (to ensure tube is not pinched) before using my 16 gram CO2 cartridge could cause the tire to over inflate and possible burst. Is this True? What is the pressure inside a CO2 cartridge before it is used?

I was never any good at Physics at school :-(

Thanks,
Alan

You don't need complex physics. Pressures simply add (in an application like this). So inflate the tire from empty or nearly empty with a CO2 cartridge and note the final pressure. Let's say you get 60psi on a tire where you need 95psi, or are 35psi short. Then you want to pre-pump to 35psi, and use the cartridge to top off at 95psi.

Of course this assumes same size cartridge and tire, but once you've dialed it in you can rely on it.

With a presta valve, all you need to make sure the tube doesn't get pinched are your lungs.

CO2 cartridges are filled to about 900 psi.

Thanks FBinNY, but what if I inflate the tire to 30psi with a hand pump before using the CO2 cartridge and a 16g cartridge is designed to inflate the tire to approx 100psi. Will the final pressure be 130psi?

Thanks,
Alan

Yes, assuming that it would have inflated that size tire to 100psi. If thats your situation, you have options.

You could save money by changing to 12g cartridges. Or you could inflate the tire to 10-30psi to seat it and make sure all is OK, then let the air back out to 5-10psi before using the CO2.

Yes, the final pressure will be 130 lbs, assuming you get all the CO2 in. Usually you loose some CO2 with inflation. But you don't need anywhere near 30 lbs to start and checking the tube isn't pinched. 5 lbs is enough.

Don't forget that the final inflation pressure a CO2 cartridge is inversely proportional the volume of the tire. Rather than worry about the volume, you can compare likely inflation pressures by comparing the squares of the diameters. For example, a tire 1.4 times wider will have double the volume, and fill to half the pressure.

This is why I suggested you start by establishing a base line for your specific tire by filling if from near empty.

Yes.

inherited co2 inflator and bringing it on family camping trip, so I'm catching up with a little research. please excuse my ignorance. I realize it's one tank per tire but can't you inflate until you think you are close, stop, check with gauge, then inflate more if nec? don't inflators have a way to stop inflation without losing what's left in the tank?

CO2 liquifies at 870 psi. As long as there is liquid at ~room temperature it is capable of producing a pressure of 870 psi.

Main goal of CO2 is to fix your flat a little faster and get on, forget about actually pumping it up to your normal pressure get in what you fill is needed to ride on for now.
CO2 will be deflating by the next day anyways if not almost flat again, remove CO2 air and pump it back up with your floor pump when you get back home.

I guess you can over inflate but that depends on what size tire you are using it on and CO2 size, your more likely to burst your tube because the tire is not seated correctly.

Some do have a way to partly use a cartridge, stop and finish, some don't. However many fiund that even if the unit is supposed to work that way, it doesn't always work out.

There's also the issue of seating, and the possibility of having to bleed ressure, reseat and fill anew. I strongly suggest a hand pump of some kind as a back up, and you can use that for the seating inflation up to 10-20psi, then if all is OL to finish with CO@.

If time is critrical, (tri-athlete in a race) and/or you have confidence that your tires seat right every time, then a straight shot with CO2 is fine.

CO2 cartridges contain liquid CO2 and are filled by weight, not pressure. Liquid CO2 will always stabilize around 900PSI (Depending greatly on temperature) no matter how full it is, until it's nearly empty.

Same reason they fill propane tanks on a scale instead of using a regulator - some gasses don't work that way.

Any gas that liquifies within the working pressure range of the container has to be sold by weight, because once you reach the liquification pressure any added gas liquifies, and while the percentage of liquid to gas changes, the pressure is constant.

As you draw off gas the liquid boils to maintain the gas pressure until there's no more liquid, then the pressure drops steadily.