By Jim Langley

Not long ago, when we were discussing frame pumps and CO2 cartridges, RBR Editor John Marsh shared this ride story with me. Perhaps something similar has happened to you:

“I was with a buddy recently who seemed to have never used his CO2 system before (or I guess it had been so long he had totally forgotten how).

"When it came time to inflate his fixed flat, he actually still had an old, used CO2 canister attached to the chuck – and didn’t really know how to use the chuck, either. He actually cut his hand in the process and froze the chuck onto the canister (which might have explained why the old one was there in the first place!). This is a very experienced rider, BTW.

"The result was that I had a full 10 minutes of standing there holding my buddy’s bike up as he fiddled with the wheel and tire, trying to air it! Let’s offer some tips to help roadies choose and use a good CO2 inflator – and emphasize the importance of knowing how it works before they need it!”

Great idea, John. First, I’ll explain what CO2 inflators are and why they’re so popular, and then offer some tips, including yours.

Tiny portable air compressors

Well, a CO2 inflator isn’t really an air compressor, because it doesn’t have a pumping mechanism to compress and store air. But it does inflate tires in a jiffy with a powerful burst of compressed carbon dioxide gas. So no pumping is involved. You just connect the CO2 inflator to the valve, release the CO2 and, almost immediately, the tire is fully inflated.

CO2 inflators depend on small metal canisters (also called cartridges) filled with compressed CO2. You want to be sure to get the right size cartridge for your tire size. Smaller ones will fill a single road tire. The larger ones can fill two tires. When emptied, the cartridges are not refillable. Instead, you recycle them and buy more.


Unlike most manual pumps that are carried in holders next to your frame, CO2 inflators with the cartridges are so small you can easily carry them in a seat bag, pocket or pack. So they’re ideal if you’ve got a road bike you can’t fit a pump on – or don’t want to put a pump on for whatever reason.

When you have a good CO2 inflator and know how to use it, you can fix a flat a lot faster than someone with a standard hand pump. So, CO2 is great for events and races where every second counts.


For shortcomings, the CO2 cartridges are not free, and every time you run out, you need to buy more. Checking a few sources, it looks like the size to inflate a single road tire runs about $3 each.

Also, as John described, CO2 inflators can be a little trickier to use than simple hand pumps. The freezing issue he mentioned is because as the CO2 gas rushes into the tire, the gas becomes ice cold. This can freeze everything the gas touches, causing the cartridge freezing to the pump head and to metal tube valves, too.

Another issue is that the CO2’s speedy inflation can blow a tire off the rim if the tire or tube wasn’t installed correctly. For example, if you rush to fix a flat you might not quite seat the tire on the rim. A common mistake is to have a section of tube trapped beneath the tire bead.

In that scenario, if you used a CO2 to inflate the tire, the tube would likely lift the bead of the tire, expand past the tire and rim and explode spectacularly. And because the CO2 inflates so fast, it would happen so quickly you wouldn’t be able to stop it. I've heard the sound likened to a rifle shot.

CO2 inflation tips

Now that you know what can go wrong, here are a few tips for avoiding trouble and getting the best performance from a CO2 inflator.

In our conversation, John mentioned that he's a long-time CO2 user, and he noted that the variety of inflators can cause problems. I'll turn it over to him to offer a couple of tips:

“All of the inflators work differently," he said. "I’ve had some that are not nearly as intuitive or easy to use as others. That’s why I finally settled on the easiest possible (and smallest!) chuck.

"It simply screws onto the threads of the CO2 canister. Screw it all the way in to puncture the canister top, then unscrew to let the CO2 flow out and inflate the tire. Screw back in to stop the flow. There’s no valve or anything to understand or operate.

"The key – no matter what you use – is to know exactly how to use it on the road. This takes practice using it while safely at home – even if it costs you a couple CO2 cartridges.”

GenuineInnovationsMicroflatNano.WEBHere’s an example of the type of CO2 inflator John uses, Genuine Innovations' Microflate Nano.

I recommend buying spare cartridges so you always have some on hand and never discover you don’t have any on the morning of a big ride. Most riders who use CO2 always carry two cartridges (at least) on most rides.

To ensure that you never blow a tire off the rim with a CO2 inflator, check carefully after you’ve fixed a flat that the tube is fully tucked up inside the tire and that the beads of the tire are seated down inside the rim (the beads are the two rounded edges on both sides of the tire casing).

Freezing CO2 is more problematic when it’s cold outside. If it’s not very cold, it shouldn’t take too long for the metal parts to thaw, then you can separate them. Or wait a bit for the parts to thaw and then douse them with water from your bottle, which should be warm enough to thaw them faster.

Last tip! Since I still see spent CO2 cartridges tossed roadside – please remember after fixing a flat to tuck the empty canister away, bring it home and recycle it.

If you’re a CO2 user please share your best pros, cons and tips in the comments below the Newsletter version of this article.

Jim Langley is RBR's Technical Editor. He has been a pro mechanic and cycling writer for more than 40 years. He's the author of Your Home Bicycle Workshop in the RBR eBookstore. Check out his "cycling aficionado" website at, his Q&A blog and updates at Twitter. Jim's streak of consecutive cycling days has reached more than 8,000. Click to read Jim's full bio.

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