Making Sense of CO2 Inflators

First time I used a CO2 cartridge, I froze my fingers and overinflated my tire in about two seconds. Stood there with frostbitten hands and a rock-hard tire wondering what went wrong. Eventually figured out the technique. They’re genuinely useful once you know the pitfalls.

How They Actually Work

Compressed carbon dioxide in a metal cartridge. Attach to a valve adapter (the inflator head), trigger the release, gas rushes into the tire. The expansion is nearly instant — ten seconds to fill what takes minutes with a hand pump. The speed is the whole point.

When the gas releases, the cartridge gets extremely cold. Cold enough to cause frostbite if you’re gripping it bare-handed. This isn’t a theoretical warning. I learned the hard way.

Cartridge Sizes

12 gram: Usually enough for road tires up to about 80 PSI. Marginal for larger volume tires.

16 gram: The standard choice for road bikes. Fills most tires completely. What I carry.

25 gram: For larger volume tires — mountain bikes, fat bikes, plus-size gravel tires. Overkill for road use but necessary for big tires.

Threaded cartridges screw into the inflator. Non-threaded ones pierce when you push them in. Either works; it just needs to match your inflator.

The Technique

Screw or insert the cartridge into the inflator without engaging it yet. Attach the inflator head firmly to your tire valve — Presta or Schrader, make sure you have the right adapter. Then release the CO2 slowly if your inflator allows it. Some have trigger controls; some just dump everything at once.

Full blast fills the tire in seconds but risks overinflation. Controlled release lets you hit your target pressure. I aim slightly under because you can always add more air at home.

Probably should have led with this: wear gloves or use the foam grip some cartridges include. The cold is severe.

Why They’re Worth It

Speed during a flat repair. Instead of pumping for five minutes on the side of the road, you’re done in thirty seconds. For racing, group rides, or just not wanting to stand around, CO2 wins.

Compact and light. A couple cartridges weigh less than a quality mini pump and take less space in a saddle bag.

The Downsides

Single use. Each cartridge inflates one tire (sometimes barely one tire). If you flat twice, you need two cartridges. If you mess up the inflation, you’re out of luck.

CO2 escapes from tires faster than regular air. Within 24-48 hours, you’ll notice pressure drop. Replace CO2 with regular air when you get home.

Cost per use. Cartridges run $2-4 each. Over a year of flats, this adds up. A hand pump is free forever once purchased.

Inflator Types

Simple trigger: Push the cartridge in, CO2 releases until empty. Fast but no control over flow rate. Easy to overinflate.

Regulated: A valve controls CO2 release. Start and stop as needed. Lets you hit target pressure precisely. Worth the slightly higher cost.

Combo units: Some include a small hand pump as backup. Belt and suspenders approach. More weight but more security.

What I Carry

Two 16g cartridges and a small regulated inflator. Fits in my saddle bag alongside tube, levers, and multi-tool. Haven’t needed the second cartridge yet but the peace of mind is worth the few extra grams.

A mini pump lives in my bag too for races where I’d want to top off before the start. CO2 for emergencies, pump for convenience.

The Environmental Question

Single-use steel cartridges aren’t ideal environmentally. Some brands accept empties for recycling. Some riders skip CO2 entirely for this reason and use pumps exclusively. It’s a valid consideration.