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  1. #1
    Senior Member
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    I've was going through my saddle bag and got looking at my CO2 cartridges, thinking do I need to carry 12 gram or 16 gram cartridges. How much pressure will I actually get out of one of these into my Conti GP4000 23C tires? What about into the 28C's on my comuter?

    The only chart I've found that gives pressure doesn't give tire size.

    See: http://www.genuineinnovations.com/inflchart.html

    If I got a flat on a century ride, I'd rather my tires ended up with more than 80 or 90 psi.

    Has anyone actually tested the amount of pressure you get out of a CO2 Cartridge
    Last edited by bccycleguy; 03-17-06 at 10:44 AM.
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  2. #2
    Senior Member euphoria's Avatar
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    I've only used them a couple of times, but I managed to inflate a full 120psi with some chump change left over. I think the general rule is one cartridge per tire.

  3. #3
    Senior Member Stubacca's Avatar
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    12g cartridges put about 90psi in my 700x23 Michelins, which isn't quite enough for me. You might get almost 100psi if the planets align perfectly, and you don't waste a single bit of the cartridge.

    16g are closer to 125psi for me, which is spot on what I want.

  4. #4
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    16 grams are better. Sometimes the 12's will leave you with a soft tire, or the need to assist with a pump.

  5. #5
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    I've found they give you around 100. As long as you don't waste any air you should be ok and can get home. Now, if you do waste some air you might be in trouble.

  6. #6
    Dog is my co-pilot 2manybikes's Avatar
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    It depends......all 23 mm tires do not have the same volume. The shape of the inside of wheels also will vary changing the volume of the space. Also the temperature changes what you get.

    Just try it at a typical temperature on your bike.

    Edit: I just noticed you live in Canada. Don't overlook the temperature effect. Below freezing they don't even work unless you warm up the inflator and the cartridge under you coat and fill the tire very fast. Even then the pressure added is very low.
    Last edited by 2manybikes; 03-18-06 at 09:00 AM.
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  7. #7
    Senior Member TassR700's Avatar
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    I use an Innovations Second Wind that works as a pump and CO2 dispenser. I put 10-20 psi in the tube with the pump first for mounting ease, then once the tire is set run it the rest of the way up with CO2 and it is about 100-110 psi.

    Edit: that is with a 12g cartridge.
    Last edited by TassR700; 03-17-06 at 01:01 PM. Reason: extra info

  8. #8
    SNARKY MEMBER CardiacKid's Avatar
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    I have never used a 12g on my 23's but on my 25's they were only good to about 80 or 90 psi. This is really only enough to get you home or to the gas station. If I was doing a solo century, I would definitely carry a couple of 16g's. There is more than enough pressure to fill up a 23 mm tire in a 16g.

  9. #9
    Huachuca Rider webist's Avatar
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    I agree that 16 is the way to go. However, I think the pressure drops more quickly (as in overnight) with CO2 than with air. Could be my imagination. It just seems that's the case.
    Just Peddlin' Around

  10. #10
    shut up and ride
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    Quote Originally Posted by webist
    I agree that 16 is the way to go. However, I think the pressure drops more quickly (as in overnight) with CO2 than with air. Could be my imagination. It just seems that's the case.
    true. the co2 gas is more permeable than air through the wall of the inner tube. don't remember where i read that (somewhere on the internet so it must be true lol) once you get home deflate the tube and just reinflate with your floor pump

  11. #11
    It's all good!
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    I have only used the 12g cartridges and they are always a little short. I am just about out of the so I think I will try the 16g next time.

    We had a great ski trip at SilverStar this year. Beautiful country!

  12. #12
    Long-time Curmudgeon DrPete's Avatar
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    16's have worked well for me too, and I ride 700x23s. When my fiancee and I ride the tandem and our 700x28 Conti GP 4 seasons are up to 120 PSI, we keep a couple 25g cartridges handy.

    DrPete

  13. #13
    Senior Member socalrider's Avatar
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    16g for full tire pressure on a 700x23..

  14. #14
    Senior Member DieselDan's Avatar
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    I've always gone pump first route. 16g cartridges tend to blow off tires on me, as I usually put 20-30psi in the tube with a mini-pump first to seat the tire and tube, then finish up with CO2. I use 12g cartridges because of this, but I always get a properly seated tire and back on my ride instead of the poor soul sitting side the road calling someone because he only brought one 16g cartridge and pinched the tube inflating it.
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