Activities Sports & Athletics All About CO2 Cartridges and Inflators for Your Bike Tires Share PINTEREST Email Print Vibrelli Performance CO2 Inflator. Amazon Sports & Athletics Bicycling Maintenance Basics Gear Baseball Basketball Billiards Bodybuilding Bowling Boxing Car Racing Cheerleading Cricket Extreme Sports Football Golf Gymnastics Ice Hockey Martial Arts Professional Wrestling Skateboarding Skating Paintball Soccer Swimming & Diving Table Tennis Tennis Track & Field Volleyball Other Activities Learn More By David Fiedler David Fiedler is an experienced cyclist and author of "Ride Fit," a guide to cycling for fun and fitness. our editorial process David Fiedler Updated July 23, 2017 CO2 cartridges are an option some cyclists prefer when it comes to inflating tires on the road after getting a flat. But what are they and how do they work? Find out more about CO2 cartridges and the inflators that come with them and why you might want to carry them when you're out on the road. What Exactly Are CO2 Cartridges? CO2 cartridges are small metal containers, about the size of your thumb, that hold highly pressurized CO2 (carbon dioxide) gas. Though they have a variety of uses, cyclists carry them along with an adapter for use in reinflating tires that have gone flat out on a ride or for filling up new tubes after they are installed in a tire. Why Are They Useful? CO2 cartridges are popular because, in the hands of someone who knows how to use them, they quickly and easily inflate a tire that has gone flat. Literally in a matter of seconds. And in the case of road bike tires, CO2 cartridges provide inflation to the high PSI air pressure that can be difficult to achieve with many frame pumps. How CO2 Cartridges Work Regardless of the actual brand, CO2 cartridges typically work the same way. The user takes some sort of inflator/adaptor head which screws down onto the cartridge and seals itself on the cartridge as it breaks the seal on the container. By placing the inflator head on the valve of the bike tire, the cyclist can then -- by either twisting or pushing down on the inflator head -- transfer the highly pressurized CO2 from the container into the tire, causing it to rapidly inflate. While the cartridges are one-time use, the inflator head is used again and again and is one of those things that many riders typically carry with them as an essential item to take on each ride. What Are The Drawbacks? CO2 cartridges are nifty. They are light and simple to use. However, new users can find it difficult to gauge exactly how much pressure the CO2 cartridges are delivering. Many cyclists have blown out tubes by over-inflating them, but that gets easier with practice. Also, the CO2 cartridges are generally for single use, so if you've got a delicate conscience about the environment, it might bother you to cast aside the metal containers each time you inflate a tire, though recycling is an option. And finally, carrying CO2 to save weight is usually a fallacy as most cyclists I know still carry a frame pump "just in case." What Else is Helpful to Know? There are different styles of valves on bike tubes. Presta valves are the long, skinny metal valves with the little tip that unscrews to allow inflating or deflating the tube. Schrader valves are the kind you grew up with and what you also find on car tires. They have a rubber-coated stem with a spring-loaded pin inside the tip that you depress to let out air. When buying a CO2 adapter, be sure to get one that will fit either your Presta valve tubes or your Schrader valve tubes. Some adapters will fit both. Though you can buy CO2 cartridges at your local bike shop, there single cylinders will generally cost you $3-$5 each. It's generally much more cost effective to buy in bulk, either online or through a local source if you have one. In larger quantities, say 25-100, the CO2 cartridges can cost as little as $.50 each. That quantity may seem like a lot to keep on hand, but I'll go through 12-15 in a typical riding season and they stay good forever. You can also split an order with a riding buddy. Finally, CO2 cartridges come in a variety of sizes, with 12g and 16g being most common for bikes. Here's a look at which size is better and why.