CruJonesIsRad

I recently bought a Felt F75, my first bike since my mountain bike a few years ago. Well, near the end of a 20 mile ride, I had a blowout. Later that day, I went to my LBS to get a pump, and decided to get a C02 pump, as it was small, compact and newfangled. I've never used one before, though, and had a question. (I have read the instructions, and they are somewhat vague)

Are the cartridges meant to be a one-shot use, where I squeeze the trigger, which in turn fills the tube to the desired 100-120 p.s.i. automatically? I've read some archived threads about using them, and everyone said, "C02's are great. I can fill a tire in 3 seconds." I understand that they are fast, but do I need a gauge to tell if the p.s.i. is ideal, or should the single cartridge fill it to the desired level?

exas

a bit off topic, but here is a newbie quesion, how is co2 better than regular old air?

z415

I don't think it is. I just don't think it would work if they tried to cram regular air into cartridges. There are no performance advantages that I know of.

z415

Depends on the size. Smaller ones are one shot and bigger ones can fill two or three tubes. You do need a gauge to tell if the psi is correct, or just experience and a sensitive hand.

There are also concerns of temperature (pressure) because if it is colder, it'll fill you up less.. or more, my physics is hazy, but it shouldn't be anything more than a few psi unless you plan on being in the Sahara or Antarctica.

This chart should show you the average psi from a certain size cartridge:
https://www.genuineinnovations.com/yieldchart.aspx

IMO, CO2 is just a stop gap measure meant to get you home, not completely fix the problem.

Retro Grouch 

You kind of have to guess about tire pressure when using CO2. A 12 gram cartridge will inflate a road tire just enough to get you home or a 16 gram cartridge will bring it up to about regular operating pressure. A mountain bike tire has a lot more volume but you run them at lower pressure so 16 grams work about right for them too.

Somebody who has a better science background than me might explain to you the desirable property of CO2 that allows it to be stored in those little cartridges in liquid form so that you'll have enough volume as a gas to fill your tire. It also has an undesirable property. You'll have to reinflate your tire or top it off with real air the next day because the CO2 will leak out of your tire much more quickly.

reverborama

The most desirable property of CO2 cylinders is their low cost. Since they are already being made in large quantities for other purposes, you can get them cheap. If they designed something specifically for bicycles, the low production volumes would make them very expensive.

George

Fill one tire with CO2 and one with air and see which one is almost flat in 3 days. I haven't done this, but it's what I've read. They were designed to get you home.

Da Tinker

CO2 has smaller molecules than nitrogen or oxygen, so CO2 will leak out through the tube walls faster. I use CO2 for road repairs but make a point of refilling the tire with air once a floor pump is handy.

Nycycle

Good points above, They are a good way to pump up till you get to compressed air, but I wouldn't leave the stuff in the tire for good.
I hand pump my tire all the hand pump is good for then fire the CO2 into it and its enough to get me to real air. For MTBs they are great.

roval

how can CO2 have a smaller molecule when it contains 1 carbon and 2 oxygen atoms vs 2 oxygen atoms for 02? that being said i have no idea if one will leak faster than the other.

exogenous

Actually air is mostly N2, but your point remains. It turns out that molecule size is less important: CO2 is more permeable in the rubber than N2 or O2.

Da Tinker

Ionic bonds (CO2) versus covalent bonds (O2). The ionic bonds result in a smaller atomic radius. The CRC manual gives the diameters of various common molecules.

roadfix

CruJones........You need to waste a couple of cartridges practicing at home before you take it out on the road for the very first time. Hope you got the non-threaded cartridges because they're a heck of a lot cheaper than the threaded variety.

CruJonesIsRad

Yeah, I did get some practice. I wasted most of one cartridge because I didn't screw the pump all the way back together, and blew a tube on my second try. I think I've figured it out. I did go out and buy a floor pump, though, as I needed one compatible with presta valves. I've decided that the CO2 will be strictly for emergency flats. Thanks for the replies.

George

They have adaptors for the presta values for a dollar.

Boss Moniker

Dude.. CO2 is not ionic, it's covalent as well. They both have double bonds (O=C=O and O=O), so given the VSEPR model CO2 should actually be bigger. Of course, size doesn't have anything to do with it, as shown from the link above, it's the permeability/solubility in rubber that matters.

CruJonesIsRad

To tell the truth...I couldn't even find my old pump. 3 years of pretty heavy riding with my new mountain bike, and I never needed to use it. I topped off a couple times at gas stations and what-not, but I never got an actual flat.

soloban

I've seen larger CO2 cartridges at REI (I'm sure they are availiable elsewhere). They look to be double the size of a standard CO2 cartridge.

+1 on CO2 being a larger molecule.
+1 on permeability in rubber.

This leads me to ask the following questions.

1. Do the green latex tubes have the same problem w/ CO2 permeability?
2. Has anyone tried a different gas, say Helium?

Da Tinker

OK, I'll go back to Chemistry again. Here I thought it was just molecule size.

Conti did some experiments with other gases in bike tires. Turned out pure nitrogen was best, but the savings were quite small.

MrCjolsen

The only advantage of C02 over a regular pump is speed. When it's 95 degrees out, and not a tree in sight, you start to appreciate it.

Al1943

CO2 cartridges are great for on-the-road repairs. The main advantage is the small size of the equipment. A 16gr threaded cartridge will fill a road tire to about 120psi. Replace the CO2 with air and pump the tires to normal operating pressure before each ride. A floor pump with a built-in gauge is best.

Al

I_bRAD

I use a 12g cartridge for a 25% weight savings.

CyLowe97

Don't forget to open the Presta valve (unscrew it) before attempting to apply the CO2.

I blew apart an Air Chuck by forgetting to open the valve. Fortunately was riding with someone else who had an inflator.

exogenous

Also, if it's a new tire, push in the stem a little after you unscrew it to make sure it's not stuck.