What you need to fix a flat

You can repair a flat tire with three things: a tire lever (or two), a patch kit or replacement inner tube, and a way to inflate the tire again. A tire lever is a flat tool that hooks under the tire bead and pries it away from the rim so you can remove the tube. Most bikes come with one or two; if yours didn't, a plastic lever costs a few dollars at any bike shop. A patch kit lets you seal small punctures in the existing tube and costs around five dollars. A replacement tube is faster if the puncture is large or if you're in a hurry—they cost ten to twenty dollars depending on your wheel size. You'll also need a pump to reinflate the tire; a hand pump or floor pump works, though a floor pump is easier on your hands.

Before you start, identify which wheel is flat by pressing on both tires with your thumb. The flat one will feel soft or collapse under pressure. Write down your wheel size—it's printed on the tire sidewall as something like "700c" or "26 inches"—because you'll need it if you buy a replacement tube. If you have a valve cap on the tire stem, remove it and set it somewhere you won't lose it.

Key Takeaways

  • You need a tire lever, a patch kit or replacement tube, and a pump to fix a flat; all three are inexpensive and worth keeping in a small repair kit.
  • Remove the wheel from the frame, use the tire lever to pry the tire bead away from the rim, and slide the tube out completely.
  • Inspect the inside of the tire for thorns, glass, or sharp objects before you install a new or patched tube, or the flat will happen again when ready.
  • Reinstall the tube by tucking the valve stem through the rim hole first, then working the tire bead back onto the rim by hand and with the lever if needed.
  • Inflate the tire to the pressure printed on the tire sidewall, starting at a low pressure and checking that the bead seats evenly on both sides of the rim.

Remove the wheel from the frame

The method depends on how your wheel attaches. Most modern bikes have a quick-release lever on the hub (the center of the wheel). Open the lever by flipping it outward, then unscrew the opposite nut a few turns until the wheel lifts free. Some bikes have solid bolts instead; use an appropriately sized wrench to loosen them. Older bikes sometimes have a solid axle that slides through the frame—loosen the nuts on both sides until the wheel drops out.

If your bike has rim brakes (the brake pads squeeze the wheel rim), you may need to open the brake to create clearance. Look for a quick-release lever on the brake itself, or ask at a bike shop how to open yours. Disc brakes (pads that squeeze a rotor in the center of the wheel) don't need adjustment. Once the wheel is free, set it on a clean surface so the tire doesn't roll away.

Pry the tire bead away from the rim

The tire has two edges called beads that hook under the rim. You need to separate one bead from the rim to access the tube inside. Insert the flat end of your tire lever under the bead, about six inches from the valve stem, and push the handle down to pry the bead up and over the rim edge. Slide the lever around the rim, prying as you go, until one full bead is free and hanging loose.

If you have only one lever, you may need to hold the freed bead with one hand while you work the lever around with the other. If you have two levers, hook one under the bead to hold it in place, then use the second to continue prying around the rim. Work slowly and avoid pinching the tire or the rim. Once the entire bead is free, the tube will be loose inside the tire and straightforward to remove.

Remove the tube and inspect the tire

Slide the tube out of the tire, starting at the valve stem. Unscrew the valve stem nut if there is one, then push the stem through the rim hole from the inside and pull the tube free. Set the tube aside—you'll either patch it or replace it.

Now inspect the inside of the tire carefully. Run your fingers slowly along the inner surface, feeling for thorns, glass shards, or sharp objects. Look for small cuts or punctures in the tire itself. If you find a thorn or piece of glass, remove it. If the tire has a cut longer than a quarter inch, or if the sidewall is damaged, the tire cannot be safely patched and should be replaced—ask a bike shop about tire cost and installation. If the tire looks intact, you're ready to install a new or patched tube.

Patch the old tube or install a new one

If you're patching the tube you removed, locate the puncture by inflating it slightly and listening for air, or by submerging it in water and looking for bubbles. Dry the tube completely, then follow the instructions on your patch kit. Most kits require you to roughen the area around the puncture with sandpaper, explore a thin layer of rubber cement, wait a minute, then press the patch firmly onto the hole and hold it for several minutes. Let the patch cure for the time specified on the kit before reinstalling the tube.

If you're installing a new tube, inflate it slightly—just enough so it holds its shape—before putting it in the tire. This prevents twisting and makes installation easier. Whether you're using a patched or new tube, start by inserting the valve stem through the hole in the rim from the inside, then tuck the tube evenly around the inside of the tire.

Reinstall the tire bead onto the rim

Begin at the valve stem and work the tire bead back onto the rim with your hands, pushing the bead up and over the rim edge as you go around. Most of the tire will go on easily by hand. When you reach the point opposite the valve stem, the tire will be tight and difficult to push on. This is normal. Use your tire lever to pry the remaining bead onto the rim, working from both sides toward the tight spot. Be careful not to pinch the tube between the lever and the rim.

Once the entire bead is seated on the rim, check that the tube is not trapped under the bead anywhere. Run your finger around the inside edge of the tire and feel for the tube. If it's pinched, pry that section back off, reposition the tube, and reseat the bead. This step prevents the tube from being punctured during inflation.

Inflate the tire to the correct pressure

Attach your pump to the valve stem. The pressure range is printed on the tire sidewall—it usually reads something like "80–100 psi" (pounds per square inch) for a road bike or "30–50 psi" for a mountain bike. Start inflating slowly and watch the tire bead as it fills. The bead should seat evenly on both sides of the rim, creating a straight line where the tire meets the rim all the way around. If the bead is uneven on one side, stop, deflate slightly, and adjust the tube position, then reinflate.

Inflate to the middle of the pressure range printed on the tire. A floor pump with a pressure gauge makes this easier than a hand pump. Once the tire is at the correct pressure, remove the pump, reinstall the valve cap, and check the tire one more time by pressing it with your thumb—it should feel firm but not rock-hard. Reinstall the wheel on the frame, tighten the quick-release or bolts, and reopen the brakes if you closed them.

Frequently Asked Questions

What if I can't find the puncture in the tube?

If the tube won't hold air but you can't see or feel a hole, the puncture may be very small or the valve stem may be leaking. Inflate the tube again and listen closely at the valve. If air is hissing there, the valve is faulty and the tube should be replaced. If the leak is elsewhere, submerge the entire inflated tube in water and watch for bubbles—they'll show you exactly where the hole is.

Can I ride the bike when ready after patching the tube?

Yes, once the patch has cured for the time specified on the kit—usually five to ten minutes—the repair is complete. Start with a short ride to make sure the tire holds pressure. If the tire loses air, stop and check that the bead is seated evenly on the rim and that the tube isn't pinched.

What if the tire won't seat on the rim no matter what I do?

The bead may be twisted or the tube may be too large for your wheel size. Deflate completely, remove the tire, and inspect the tube for the size marking. If it's wrong, replace it with the correct size for your wheel. If the size is correct, reinstall the tube carefully, making sure it's not twisted, and try again.

Do I need to replace the tire if it has a small puncture?

A small puncture in the tire tread (the part that touches the ground) can be patched from the inside using a tube patch. A puncture in the sidewall or a cut longer than a quarter inch cannot be safely repaired and the tire should be replaced. When in doubt, ask a bike shop to inspect it.

How do I know if I'm inflating to the right pressure?

The pressure range is always printed on the tire sidewall. Use a pump with a built-in gauge, or buy an inexpensive pressure gauge at a bike shop for a few dollars. Inflate to somewhere in the middle of the range—higher pressure for lighter weight and speed, lower pressure for comfort and traction.