Using a CO2 Inflator on a Bike Tire Explained

Jim’s Tech Talk

By Jim Langley

Earlier this week, I answered a question from a roadie who wondered about the tire inflation capability of his and his friend’s CO2 inflators. Since I only use them infrequently, I hope you CO2 aficionados will read the question and my answer and give your opinion. Please also share your favorite CO2 inflator.

If you don’t know what a CO2 inflator is and want to learn more, here’s a video from Genuine Innovations, longtime makers of these tiny inflators so you can see one in action.

As you can see in the video, these CO2s are powerful minis that inflate tires extremely quickly. This is why CO2 pumps are so popular. They fit in a pocket or bag for quick access and the compressed gas inflates tires in seconds (no pumping required) – and may even be able to inflate to higher pressures than some mechanical pumps.

Here is a link to the Genuine Innovations Microflate Nano for more ($22.29): https://www.genuineinnovations.com/collections/bicycle-co2-tire-inflators/products/microflate-nano-co2-bike- tire pump. Many other companies also manufacture these inflators.

The main obstacle to these inflators is that you have to buy the cartridges

The question of “Mark”

During a group training today, I met a friend. He was doing a solo ride to our furthest point from home. He had just fixed a puncture on his new Canyon Ultimate CFR with DT Swiss PRC 1100 Dicut Mon Chasseral rims and Schwalbe Pro One TT 28mm tires.

Our practice ride started again and my friend headed home.

Later, when I called him, he told me that on the way back, his bike seemed weird. He said he looked down and the rear wheel looked fake. Stopping to examine it, he discovered that the tire was not fully seated after re-inflating the tire with a 16g CO2 cartridge.

It reminded me that two weeks ago I had a flat tire after hitting glass. I neatly attached my CO2 cartridge (also 16g), held it there until the pressure equalized, and removed it neatly. After getting home I checked the pressure and found only 60 lbs in my 700 x 28mm tires. I inflated them and they held up for the last two weeks with an acceptable level of normal pressure drop, so the cartridge only had the capacity to inflate my tires to 60 lbs.

My friend also used a 16g CO2 cartridge.

So my questions for you are:

  • Is it possible that the volume of the 28mm tires is too big to fill them over 85 pounds with a 16g cartridge reliably?
  • If a 16g CO2 cartridge can’t properly inflate a 28mm tire, is it possible that it can’t generate the pressure needed to seat certain tire/wheel combinations?
  • Should people using 28mm tires start carrying 20g CO2 cartridges?

Thanks Jim!”

My answer

I had to dig a bit to try to find a good answer to these questions. Unfortunately, I couldn’t find anything super specific or helpful. But as far as I can tell the 16g cartridges are supposed to be able to inflate tires to 88psi – see Genuine’s inflation chart:

So, if that’s true, I think your friend’s tire seating problem may have been an installation issue or a tight tire situation. So many tire manufacturers now undersize tires, making them much tougher on seats, especially with tubeless-ready tires. So my best guess is that it wasn’t so much air pressure and probably just part of the tire stuck and refusing to stand up and sit down.

With your tire underinflated and possibly with the tire that wouldn’t sit if it was too soft and not fully inflated, the other wild cards are CO2 cartridges and their use. I don’t know if all cartridges are made the same. Maybe some are not as full as others? Or maybe some don’t release the air as quickly and completely as others?

And, I think we’ve all had times when the CO2 pumps didn’t seal as well and we lost pressure or maybe the valve had some issues like unscrewing the valve core a bit when we have removed a screw-on CO2 inflator or lost air by removing a press-fit.

These are my best guesses as to what might happen. And, since it happened, I don’t see anything wrong with carrying around the next larger CO2 cartridge just for a little insurance. But you’ll want to have an inflator with a shut-off valve so you don’t over-inflate by mistake.

Especially with wide rubber like anything over 32mm, over inflation can lead to a scary explosion if you blow the tire off the rim. I speak from experience: https://www.roadbikerider.com/overinflation-explosion-a-cautionary-tale-about-very-wide-tires/.

Your turn

Ok readers, please leave a comment with your best answers and tips for CO2 inflators and how to use them. Your favorite inflators (makes and models) and replacement cartridges would be especially helpful. Thanks!


Jim Langley is RBR’s Technical Writer. He has been a professional mechanic and cycling writer for over 40 years. He is the author of Your Bike Workshop at Home in the RBR electronic library. Check out his “Cycling Enthusiast” website at http://www.jimangley.nethis Q&A Blog and updates on Twitter. Jim’s cycling streak ended in February 2022 with a total of 10,269 consecutive daily rides (28 years, 1 month and 11 days without ever missing a ride). Click to read Jim’s Full Biography.

Earnest L. Veasey