Flat tires happen. Knowing how to swap a tube yourself turns a ride-ending problem into a 10-minute pit stop. This tutorial from Park Tool's Calvin Jones covers the full process from start to finish, including how to figure out what caused the flat so it doesn't happen again.
The same technique works on road bikes, mountain bikes, and hybrids. All you need is a set of tire levers, a spare tube, and a pump.
You need three things: tire levers, a spare inner tube, and a pump. A CO2 cartridge works instead of a pump if you're on the road. Carry all of these on every ride.
If you don't have a spare tube, you can patch the damaged one to get home. But swapping in a fresh tube is faster and more reliable.
Remove the dust cap from the valve. For Presta valves, loosen the small nut at the tip and press down to release air. For Schrader valves (the same kind on car tires), push the pin inside the valve with a small tool or the end of a tire lever.
Squeeze the tire all the way around to force out any remaining air. The tube needs to be totally flat before the tire will come off the rim.
Tip
If your wheel has a Presta valve with a threaded stem nut, loosen and remove that nut before trying to pull the tube out later.
Push both sides of the tire toward the center of the rim. This loosens the bead from the rim sidewall and gives you slack to work with.
Hook one tire lever under the bead anywhere except right at the valve. Pull back to lift the bead out of the rim. Place a second lever a few inches away and do the same. Once two sections are free, you can usually run a lever around the rest of the bead to pop it off. Pull the second bead off and remove the tire and tube from the wheel.
Inflate the old tube to about twice its normal width. This makes even tiny pinholes detectable. Run your hands slowly around the tube, listening and feeling for escaping air. If you can't find it by feel, dunk the tube in a bucket of water and look for bubbles.
The type of hole tells you what happened. A tiny pinhole means a thorn or piece of wire. Two parallel cuts side by side (called snake bites) mean you hit a pothole or ran too-low pressure. A large shredded hole is a blowout from a damaged tire casing.
Tip
Mark the hole location before deflating the tube. If you plan to patch it later, you won't have to find the hole again.
Run your fingers carefully along the inside of the tire. Feel for thorns, glass, or wire stuck in the casing. If something punctured the tube, it's probably still embedded in the tire and will puncture your new tube too.
Check the rim strip that covers the spoke holes. If the strip is damaged or shifted, the spoke ends will poke into the tube under pressure. Look for any spokes that are too long and sticking through.
Tip
If the tire casing has a rip or tear, use a tire boot as a temporary fix. It's a patch that goes inside the tire to keep the tube from poking through the gap.
Unfold the new tube and pump just enough air into it so it holds its shape. This prevents it from getting pinched or folded when you install it. Tuck the tube into the tire all the way around.
Feed the valve stem straight through the rim hole. Make sure it goes in straight, not at an angle. A crooked valve will get cut by the rim hole over time. Line up the valve with the tire's pressure label printed on the sidewall so you can find it later.
Push one bead at a time onto the rim by hand. Start at the valve and work around both sides until you meet at the opposite end. Before starting the second bead, make sure the tube is fully tucked inside the tire body.
The last section of the second bead is the tightest part. If you can't get it on by hand, use a tire lever carefully. Go slow - pinching the tube between the lever and rim means you'll be doing this whole process again.
Add a small amount of air and inspect the bead seat line all the way around the rim on both sides. The line should sit at the same height everywhere. If the bead pops up in one spot, deflate and push it back down. If it dips, try adding more air or apply soapy water as a lubricant to help it seat. Never use grease or oil.
Once the bead is evenly seated, inflate to the pressure printed on the tire sidewall. Tighten the valve lock nut and install the cap. You're ready to ride.
