When mountain biking, flat tires are inevitable. When charging through rocky terrain or roots, or just riding fast flow, the tires on your bike are pushed to the limit. Changing a flat tire is basic knowledge that all mountain bikers should have. The ability to fix a flat out on the trail saves you from the pain and embarrassment of having to push your bike home.

Types of Flat Tires

While the steps to change a flat tire will be the same, it is useful to know what type of flat tire you have.

Puncture

These types of flats are the most common. They are caused by a sharp stick, rock, thorn, or other sharp objects puncturing through both the tube and the tire. They are often in the tread of the tire and are characterized by a single hole in both tube and tire.

Pinch Flat

A pinch flat is caused when the tire is at a low pressure and the tube gets pinched between the rim and a square object such as a rock. Pinch flats result in two holes in your tube that look like a snake bite. Running tubeless will prevent all pinch flats.

Tools

To change a flat tire you need to carry a few tools and supplies while riding.

The Essentials

• Spare tube: Whether you are running tubes or tubeless, you will need a spare tube to fix your flat.
• Hand pump/CO2 cartridge: A pump or CO2 is how you will reinflate your flat tire. When buying a pump or CO2 adapter, be sure that the valve is compatible with your tubes. The most universal valve is a presta valve.
• Tire lever: A tire lever is not necessary if you have forearms like Popeye, but always helps to remove a stubborn tire from your rim.

Optional Tools

• Bacon strips/tire plugs: These plugs are used with tubeless tires to plug small holes that the sealant is unable to seal on its own. These are a good thing to carry for smaller punctures.
• Tire boot: If the sidewall of your tire is severely compromised, a tire boot will allow the new tube to be inflated without pushing out of the side of the tire.
• Patch kit: A patch kit can be used to patch a tube. This process is often slow and not recommended for a trailside fix.

All of these tools, essentials and other related products can be found at your local bike shop.

Changing a Flat

1. Remove the wheel from the bike

Loosen or remove the axle, then remove the wheel. If your bike has rim brakes, be sure to open the brakes to give yourself room to take off the wheel. If your bike has disc brakes, DO NOT squeeze the brake lever once your wheel is off. This will cause your brake pads to extend too far and will make reinstallation impossible. If you are removing the rear wheel, shift your drivetrain into the small cog to make it easier to remove the wheel from the chain.

2. Take the tire off the rim

Release any remaining air from your tire to allow for an easy tire removal. Pinch the tire on one side of the rim to remove the tire bead from the rim, leave the other side of the tire on the bead. The one side of the tire should now have room for your tire lever. Use the tire lever to pull the one side of the tire over the rim, giving access to the flat tube or sealant if you’re tubeless.

3. Remove the old tube

Once one side of the tire is off the rim, you can remove the flat tube, or the valve stem if you’re tubeless. Be sure to hold onto these items - the valve stem will be required to set up your tire tubeless again, and the old tube can be patched to create a new spare tube.

4. Inspect the inside of the tire

If you have a puncture, look inside the tire for a rock or anything inside the tire that can puncture a new tube.

5. Replace with new tube and reseat tire

Put the new tube in the tire. Add a small amount of air to the tube to give it a little bit of shape and make it easier to align without folds. Pull the tire back over the rim so both sides of the tire are inside the rim. Be sure not to pinch the new tube between the bead of the tire and the rim. Sometimes a tire lever can be used to help stretch the tire back over the rim. Be careful not to puncture your tubeless tape or rim strip when using the tire lever.

6. Reinflate and replace wheel

Using a pump or CO2, reinflate the tire to your preferred tire pressure and replace the wheel. Be sure to check that the axle is tight and that the tire is holding air.

Tubeless Tips

Going tubeless is one of the best ways to reduce the number of flat tires and make fixing flats easier. Catastrophic tubeless failures still require a replacement tube but some punctures can be sealed without taking the wheel off of the bike. If you notice a small puncture in a tubeless wheel that the sealant isn’t holding, use a bacon strip or tire plug to fill these small holes. Plug the hole, rotate the wheel so that the puncture is facing down or spin the wheel to force sealant into the puncture. Once the tire is holding air, check your tire pressure and continue riding. These plugs will often last until you need a new tire.

Knowing how to fix your flat tire on the side of the trail is a crucial tool to keep you riding and having fun. Now get out there and go for a ride!