Something I read in Bicycling yesterday while waiting in a dentist office. CO2 dissolves into butyl, it claimed. So if you fill your tires with a CO2 cartridge you may have to top them off again even before your ride is over. To which I reply Really? I had never heard such a thing, but then I have always used a pump. N2 and O2 do not do that (it said), and since they make up most of the atmosphere, if you use a pump you won't have that problem. That's what it said.

Is this news to only me?

Ran across this a few years back. I've noticed that CO2-inflated tires lose significant pressure overnight...

https://www.velonews.com/2009/02/bik...t-frames_87175

In the aquarium world CO2 requires special tubing because the CO2 will seep out of average air tubing. Perhaps the molecules are smaller than those in air and butyl tubing is more porous to those smaller molecules, thus going soft after a few days.

So--- does this mean that butyl inner tubes are a carbon trap? And by exclusively using butyl and CO2 cartridges, cyclists could contribute to the slowing of global warming? If so, we need to stop the sale of all floor, mini, frame and hand pumps!

Actually the CO2 molecules are larger than either O2 or N2 molecules (the dominant components in air) but they diffuse through rubber faster due to their chemical affinity to the hydrocarbons in rubber. So they tend to stick to the rubber tube wall and then gradually diffuse through to the outside whereas the smaller O2 and N2 molecules bounce off and stay inside the tube better. But it would take either a very long ride or extremely thin tube for the pressure to drop enough to require pumping it up again before getting home. Usually a tube filled with CO2 will be fine for the entire ride but will lose air faster over the next few days in comparison with the same tube filled with air - and one filled with N2 will lose pressure even slower.

wholesalers in the Netherlands say that in the past two years there has been a 400% rise in sales of nitrous oxide



wait, what were we talking about?

I'll never understand folks who carry CO2 inflators instead of pumps. I've lost count of how many times I've had to "rescue" folks on the side of the road who'd accidentally emptied their CO2 cartridges to the atmosphere (either due to fumbling, or having the inflator/cartridge attachment fail) while trying to inflate their tires. How much weight are they saving anyway? My gigantic Silca pump with metal Campy head weight 5.5 oz while some minipumps weigh as little as 4 oz. An inflator with two CO2 cartridges weighs about 2.5 oz, so they are sacrificing reliability for the sake of 1.5 oz. Ridiculous I say!

FWIW, I tell my customers that the CO2 fill is only to get them to a source of compressed air. At the end of the ride deflate the tube and re-fill with air.

Top

Ah, but you're comparing with a minipump. My Silca and Zefal full-size pumps will inflate a tire almost as fast as a CO2 cartridge, for the cost of an extra 3 oz. They're also useful for fending off errant hounds or slipping into the spokes of a cyclist trying to pass (Breaking Away reference). Try that with a CO2 inflator!

I want to see pics of your arms. They must be HUGE.

Popeye's got nothing on me!

They old full size frame pumps were indeed pretty fast. Never timed it but surely not more than 2 minutes to pump a tire from empty. CO2 inflators were the direct result of the ridiculousness of mini pumps. I have to say I have become mesmerized by the convenience and speed of inflators, after resisting them for a long time. I always carry a mini pump as a back up though.

I still have a Zefal HP I've had since forever. I had a Silca frame pump with campy head as my main pump for like a couple decades, but it was stolen a while back when my bikes were in storage. I admit I have used them to fend off mean dogs. (if and only if I was about to get bitten - a squirt from the water bottle works 95% of the time)

+1

Buying CO2 in a cartridge is as wasteful as buying water in a plastic bottle.

Last time I pulled over to help someone with a CO2 fubar I told them they could use my pump only if they promised to stop buying those cartridges.

I've got a separated shoulder and I can still fill up my tire in less than a minute.

I think having a pump as a backup to a CO2 cartridge has got it backwards. Your CO2 cartridge works once. Riding out to French Fender Day I accidentally bumped my Lezyne pump off the frame pegs. A car ran over it. It still works.

Man, you guys are harshing my mellow. I guess you're right it is wasteful, but compared to a lot of things it's pretty small. I do watch my trash footprint in general. I always patch tubes multiple times before tossing. I don't buy bottled water, or powerbars for that matter.

I only got talked into trying an inflator 6 months ago. Under one minute with a Lezyne road drive??? No way I can do that. Takes me like 250 pumps, and tires are still not up to full pressure. It might be because I still use 90+ psi for 28c tires. I've got to put new tires on this weekend. Maybe I'll do one with the road drive and count and time it. One minute might be enough to hobble home, but that's it. With an inflator it's like 3 seconds and you've got full pressure.

Supposedly there are refillable CO2 cartridges. I wonder if there are any you can fill up with air at home, and that will work with an inflator. There's your Rube Goldberg solution...

No! No! No! You've got it backwards. If you used butyl to trap CO2 it would escape!

I didn't ask to raise the question of CO2 vs. pumps, either mini or frame. I'd just never heard that point before, wondered how universally known it was or if it was a recent "discovery" in the bike world. (The seem to discover new things all the time, like heavier bikes are better than light ones, but that's for another day.)

I'm a full-size frame pump person. I can fill a tire to rideable levels in a minute or less. That's insignificant compared to the time it takes to swap out or repair a tube. I can even get 140psi if I'm willing to.

Edit: See the conversation I had with [MENTION=456494]prat[/MENTION]hman in post #36 this thread. I apparently have a mistake in what I said, the CO2 molecule is not polarized, and I have no clue why the CO2 behaves differently from N2 and O2.

What follows is the original paragraph I wrote. end edit.

No. It's news to me that CO2 actually isn't contained by butyl rubber, but it's not surprising that it is different from N2 or O2. The CO2 molecule has two oxygen atoms at roughly a 120 degree angle apart from each other, relative to the carbon atom. Hence it is polarized due to it's shape. N2 and O2 each have only two atoms of the same species, so they are not polarized anywhere so strongly. The polarization has to do with some kind of difference in how the protons and neutrons are distributed in the CO2. It's not uniform in any event and hence the molecule has what's called a dipole moment. This parameter affects mild chemistry issues like solubility and strong chemistry issues (in some materials) like what it will react with, at least for most molecules. CO2 is rather stable and hard to create a chemical reaction, in any event.

Somebody stop me! Who'd a thunk my college chem would have any use in bikie chatter????

Yes, I'm surprised at what the CO2 does, but not surprised it behaves differently from nitrogen and oxygen.

Did you find out what your dentist rides (the important stuff!)?

CO2 is at least partially a liquid when it's at high pressure in the cartridges. So the CO2 expands into way more gas volume than a similar cartridge with just compressed air in it.

The newer style screw-on CO2 inflators are much less prone to goofs and bad technique. They reliably fill the tires instead of spraying CO2 all over. The usual recommendation is to carry a Genuine Innovations Air Chuck. It's extremely small, too. And there's other similar inflators available.

Yes, the full size frame pumps are very fast. Too bad that newer bike frames often don't have good mounting locations for them.

I counted 200 pumping strokes on my Topeak Mini Morph pump, and that was just to get a 25mm tire up to rideable pressures, around 70 to 80 psi. Tedious, but it never runs out of air. I only bring it as a backup on long solo rides now. CO2 and one spare tube is enough for most of my riding -- I only get a couple of flats a year.

I'm looking for the statement "a heavy bicycle hugs the road."

Wait! Wait! WAIT!!!! Is not CO2 heaver than regular old air? Why would a serious weight conscience bicyclist every use CO2 in their tires? CO2 would slow down the rotational rate of their wheels!

LOL, yeah not buying that! And I say this as someone who carries a full size ZEFAL on pretty much all my bikes. But I also carry a CO2 inflator. The pump is now a backup as the CO2 gets me back up and riding so much faster and easier.

I converted from being a die hard frame pump guy to CO2. The reason was the amount of energy needed to pump a tire in 90+ degree weather with 95% humidity. The kicker was the flat as a result of pumping, then needing to patch. The other part of the consideration was the rubbing of the pump on the paint and the occasional miss of reaching for the DT shifter and knocking the pump off the peg. Oh and did I mention the rattle it makes? Then there is the SS/FS bike that doesn't have any accessories except a bag under the saddle where 3 CO2 cartridges reside with the 15mm wrench, etc.
[MENTION=28632]Road Fan[/MENTION] - thanks for the explanation! I do appreciate the mechanics of the chemistry. Always enjoyed understanding molecular structure as well as metallurgy.

Colnago carbon. Full Campy EPS. Enve wheels.

Full dentist.