Jim’s Tech Talk
By Jim Langley
Early this week I answered a question from a roadie wondering about the tire inflation capacity of his and his friend’s CO2 inflators. Since I only rarely use them, I’m hoping you CO2 aficionados will read the question and my answer and weigh in with your advice. Please share your favorite CO2 inflator, too.
If you don’t know what a CO2 inflator is and want to learn about them, here’s a video from Genuine Innovations, longtime makers of these tiny inflators so that you can watch one in action.
As you can see in the vid, these CO2s are mighty minis that air up tires extremely fast. That’s why CO2 pumps are so popular. They fit in a pocket or pack for quick access and the compressed gas blows tires up in seconds (no pumping required) – and may even be able to inflate to higher pressures than some mechanical pumps.
Here’s a link to the Genuine Innovations Microflate Nano to learn more about it ($22.29): https://www.genuineinnovations.com/collections/bicycle-co2-tire-inflators/products/microflate-nano-co2-bike-tire-inflator. Many other companies make these inflators, too.
The main knock against these inflators is that you need to buy the cartridges
While on a group training ride today I ran into a friend. He was on a solo ride at our furthest point from home. He had just repaired a flat on his new Canyon Ultimate CFR with DT Swiss PRC 1100 Dicut Mon Chasseral rims and Schwalbe Pro One TT 28mm tires.
Our training ride started up again and my friend set course for home.
Later when I called him he said that on the way home his bike felt odd. He said he looked down and the rear wheel appeared to be out of true. Stopping to examine it he found the tire hadn’t seated fully after reinflating the tire with a 16g CO2 cartridge.
That reminded me that two weeks ago I flatted after hitting glass. I attached my CO2 cartridge (also 16g) cleanly, held it on until the pressure equalized, and removed it cleanly. After getting home I checked the pressure and found only 60 lb in my 700 x 28mm tires. I pumped them up and they’ve held for the past two weeks with an acceptable level of normal pressure drop, so the cartridge only had the capacity to inflate my tires to 60 lb.
My friend also used a 16g CO2 cartridge.
So my questions for you are:
- Is it possible that the volume of 28mm tires is too great to fill them to 85-plus pounds with a 16g cartridge reliably?
- If a 16g CO2 cartridge can’t adequately inflate a 28mm tire, is it possible it can’t generate the pressure to seat certain tire/wheel combinations?
- Should people running 28mm tires start carrying 20g Co2 cartridges?
I had to do a little digging trying 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, 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 companies now are undersizing tires making them way more seat-resistant, especially with tubeless-ready tires. So, my best guess is that it wasn’t so much not enough air pressure and probably just a part of the tire stuck and refusing to pop up and seat.
With your under-inflated tire and maybe with the tire that wouldn’t seat if it too was soft and not fully pumped up, the other wildcards are the CO2 cartridges and the use of them. I don’t know if all cartridges are made the same. Maybe some aren’t as full as others? Or maybe some don’t release the air as quickly and fully as others?
And, I think we’ve all had times when CO2 pumps didn’t seal that well and we lost some pressure or the valve might have had issues like unscrewing the valve core a little when we removed a screw-on CO2 inflator or lost air removing a press-fit one.
Those are my best guesses as to what might be going on. And, since it happened, I don’t see anything wrong with carrying 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 inflating can result in 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/.
Okay readers, please leave a comment with your best answers and advice for CO2 inflators and their use. Especially useful would be your favorite inflators (brands and models) and replacement cartridges. Thank you!
Jim Langley is RBR’s Technical Editor. A pro mechanic & cycling writer for more than 40 years, he’s the author of Your Home Bicycle Workshop in the RBR eBookstore. Tune in to Jim’s popular YouTube channel for wheel building & bike repair how-to’s. Jim’s also known for his cycling streak that ended in February 2022 with a total of 10,269 consecutive daily rides (28 years, 1 month and 11 days of never missing a ride). Click to read Jim’s full bio.