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Okay, I admit. I'm a newbie when it comes to co2.(10 posts)

Okay, I admit. I'm a newbie when it comes to co2.Ken of Fresno
Apr 14, 2003 12:50 PM
My Sierra Trading Post order came in a while back along with my co2 inflator. I figured I'd better test this thing out at home, so I can know what's up when I really need to use it. With the stuff being only 40 cents a pop from Walmart I can afford to waste a few. Worked great the first time. Up to 115 psi in no time flat. Okay, so a couple days later I go out for a 35 mile fairly quick ride. I noticed I was working a little harder than usual, but since I felt pretty good I just kept plugging away. It wasn't until I was about 5 miles from home that noticed my tire was low. Dangerously low. At first I thought I had a flat, but it wasn't getting any faltter. Then, I remember someone saying that co2 doesn't keep pressure as long as air. I popped another cartridge in just to get safely home. Don't think I had a puncture. Any of you experienced co2 users have any thoughts on this (aside from the obvious bit of advice to alway check the pressure in the tires before each ride)?

re: Okay, I admit. I'm a newbie when it comes to co2.BigPete
Apr 14, 2003 1:05 PM
Its been my experience that tires filled with CO2 generally lose their pressure much faster. If I've had a flat and have used CO2 to reinflate the tire what I generally do is let the pressure out and refill the tire with the floor pump when I get home from my ride.
Same Experience as Big PeteScot_Gore
Apr 14, 2003 1:32 PM
CO2 has smaller molecules than "air". It leaks through the tube material faster than your household variety air.

Re-fill with the cheap stuff after an event.


CO2 will last about a day or two...Bruno S
Apr 14, 2003 1:58 PM
After a puncture you should deflate the tire at home and inflate with air using a pump.
You had a flatKerry
Apr 14, 2003 5:59 PM
The difference in permeability between CO2 and air is minimal and not enough to cause your tire to go flat during a ride. You have a pinhole leak or you had a valve that didn't seat properly.
Not during a ride but after a couple of days...Bruno S
Apr 14, 2003 6:26 PM
I've seen this before. CO2 leaks out almost completely after a few days while air lasts much longer.
Apr 15, 2003 7:17 AM
Every time I get a flat and refil will CO2, my tire is very low again the next day. Just drain the tire and refill it with your regular pump. I pump up my tires before every ride, so I always notice when low.
No pinhole: its Fick's Law, pure gas adds a chemical pressureteamsloppy
Apr 14, 2003 7:35 PM
By filling the tube with pure CO2, there is an additional force (diffusion) moving the CO2 out of the tube into the atmoshpere. When you pump your tubes with air, this additional chemical force is vastly smaller(its the same N2/O2 mix inside and out).

Fick's Law is:
The net diffusion rate of a gas across a membrane (the tube) is proportional to the difference in partial pressure, proportional to the area of the membrane and inversely proportional to the thickness of the membrane.

The effect is similar to the comparative deflation rate of a Helium filled balloon and an air filled ballon (the pure helium balloon deflates faster).
That clears things up......I think? :-) nm.Dutchy
Apr 14, 2003 11:15 PM
No pinhole: its Fick's Law, pure gas adds a chemical pressurekevinmd
Apr 15, 2003 9:15 AM

Because your tube is now 100% CO2 and the atmosphere is <1% CO2, the gas diffuses across the semipermiable membrane (the inner tube) to try and equilibrate. Be glad this happens folks, it is how we breathe.

-- Kevin