CO2 inflators are an extremely convenient way to inflate tyres, if speed of operation is the most important factor. A small metal canister contains compressed carbon dioxide gas that expands to fill your tyre when the top is punctured. It's a quick way to get back on the road, but if you're not careful it's easy to jet all the CO2 into the atmosphere and not the tyre.
Our guide below shows you what we believe is the best method to fit and use a CO2 inflator. If there are other methods that you prefer then feel free to let everybody know in the comments.
Go through your usual tube replacement process, making sure there are no sharp objects left in the tyre and the tube isn't pinched by the tyre. The latter is very important. With a had pump, you might get a chance to see a tube popping out of the tyre and stop it, but when you use a gas canister you'll blow a hole in a pinched tube before you can react.
1 Make sure the valve is open
It's essential to have the valve in the open position. We've seen riders fit a fresh tube in a hurry and hit the CO2 trigger with the valve still closed, and so wasting a cartridge. You can avoid this by storing your spare tubes with the valves open.
2 Clear the valve
Once you've undone the valve, tap the small brass threaded chuck back towards the valve stem. Valves can be quite sticky when new, and while the power of the compressed gas is usually enough to hit the valve open it's still good practice to clear it first.
3 Make sure the inflator is closed
While each CO2 inflator is designed slightly differently, they mostly follow the same functional path. Most will have a switch, dial or trigger to allow you to control the moment of delivery. This version we're using is from Lezyne. It uses a twist dial. It's all the way open or all the way closed. Right now, you need to close the valve fully.
4 Put the cartridge in the inflator
The head unit and the cartridge are both threaded. They screw together. Some inflators allow you to store the cartridge inside a casing, primed and ready to go. You release a safety catch then pull a trigger to let the gas out. You could carry this Lezyne head with the cartridge screwed in too, but there's a slight risk of accidentally opening it.
5 Tighten the cartridge into place
Keep turning the head unit on to the cartridge. Inside the threaded port of the head unit is a small tube with a pointed end. This tube will pierce the end of the CO2 cartridge. You'll sense it in your hands as the gas escapes the confines of the cartridge and expands into the head unit. The valve trigger you closed before you started stops it from flowing out until you're ready.
6 Turn the wheel up
Bring the valve section of the wheel so that it is uppermost. Press the valve port of the head unit onto the valve stem. Make sure it's firmly on. Keep holding it.
7 Unleash the gas
Holding the inflator's head unit onto the valve stem, open the flow of gas from the inflator cartridge to the inner tube by operating the inflator's trigger, dial or button. The inflation will be very sudden, a bit noisy and it'll make the gas cartridge extremely cold; cold enough to burn skin, so wear gloves or, as we've done, take great care not to touch it.
8 Remove the inflator
When the tyre inflates you should hear the tyre beads pop to the rim signifying that the tyre has seated. It'll make a resounding snap sound. Next close the valve on the gas cartridge. Most allow you store unused gas in the cartridge. In most cases we use all the gas to ensure tyre seating. Pull the inflator off the inner tube valve and adjust to your favoured pressure, then close the inner tube valve.