C02 cartridges are only for "temporary" air ... WHO KNEW?!!!!

[Eden]

I'm pretty sure this is true. If I fix a flat with co2 I always have to pump the tire up the next day. I wouldn't say they get totally flat, but pretty squishy. Still I love having cartridges over a hand pump on the road. I still carry a really small pump for emergencies, but there's nothing like changing a flat in 40 degree rain and having to pump and pump and pump with a little hand pump just to get 70 lbs of pressure. Blech - co2 is so much quicker.

Even plain old air leaks out slowly, if I let my tires go a week without pumping them up they'll go from 100 lbs to 80.. its just not as much or as noticeable as the loss with co2.

[OakLeaf]

Well I was skeptical when I first read this, but after I thought about it...

Race cars fill their tires with nitrogen... NOT because it doesn't heat up the same as room air as a lot of people believe... but because it doesn't escape the tires as quickly as room air.

According to a trade organization (fwiw), oxygen escapes through tires 3-4 times as fast as nitrogen. It doesn't give statistics for CO2 (which would have to be somewhat slower than oxygen), but it does say that nitrogen is the largest molecule in room air.

Bottom line is, it's a bigger deal for a car, since you air your bicycle and motorcycle tires before every ride anyhow, but you probably don't check your car tires daily. But yeah, I suppose now that I've read this, if I have a flat early on a long ride, I'd probably borrow someone's air pump within a few hours.

[SouthernBelle]

The drastic temperature changes the co2 goes through may affect all this too.

Just a thought,

[Fujichants]

I have to agree that this is true as well, and BF agrees. Whenever we had flats, we would fill up with CO2 and the next day the tire would be soft and have less air in it. CO2 is perfect to get you home.

Anyways, I always always always pump my tires before a ride. Personally I just feel as if i'm missing something if I don't.

[Aggie_Ama]

I always pump before my rides so the CO2 issue is pretty much null for me which may be why I say rubbish to it but I still haven't seen a true flat overnight with CO2.

Why pump before every ride? It is kind like how as a kid our parents make us brush every night, it is good for you yes but it also becomes habit. It just makes sense to check with a tire pressure valve every ride so I don't have to deal with pinch flat which pisses me off more than any other flat because it is so easily avoided. I cannot even count the number of times my tire feels okay to the touch but I put the pressure valve on it and it is only 80-90 PSI. Also I get so scatter brained some days I wouldn't remember if I did put more air last ride, two rides, last year. LOL. My 2 cents threadjack.

[Grog]

I have noticed that CO2 escapes a lot faster than regular air out of my tubes. It's not constant though and I suspect this may have something to do with the tubes as well (I have a batch of light racing tubes that seem to be leaking faster than my heavier tubes but maybe it's skewed perception).

I always pump up my road tires before rides anyway. If I've inflated it with CO2 the day before and it's particularly low when I start pumping, I empty it almost entirely and start again with "fresh air."

[Mistie]

N2 is a smaller molecule (2 atoms of N) than CO2 (1 atom of C and 2 of O). However, because our atmosphere is 78% N2, the N2 would escape more slowly because of the principle of diffusion. Thus, CO2 would escape quickly because there is less than 1% CO2 in the atmosphere and to reach equlibrium, the CO2 would have to move OUT of the tire. In the case of N2, equilbrium is reached quicker because there is more N2 in the outside of the tire (atmosphere). Sorry for the chemistry lesson, I have a BS in it.