What you need to fix a flat tire

A flat tire can be repaired in two ways: you can patch the inner tube if the hole is small, or replace the tube entirely if the damage is too large. Most people carry a patch kit and tire levers on rides so they can fix a flat roadside. At home, you have the option to work slowly with basic tools or take the wheel to a bike shop.

To patch a tube, you will need a patch kit (which includes patches, sandpaper, and adhesive), tire levers to remove the tire from the rim, and a way to inflate the tire again—either a hand pump or access to an air pump. If you are replacing the tube instead, you need only a new inner tube that matches your tire size and a pump. Tire size is printed on the sidewall of your tire, usually as something like "700x25c" or "26x2.0".

Before you start, lay out all your tools and the wheel on a clean, dry surface. If the tire is still on the bike, remove the wheel first by opening the quick-release lever or unscrewing the axle nuts, depending on your bike's design.

Key Takeaways

  • Tire levers and a patch kit are the minimum tools needed to repair a flat roadside; a hand pump is essential because you cannot inflate a tire by mouth.
  • The first step is always to find the hole by inflating the tube slightly and listening or feeling for air, or by submerging it in water to see bubbles.
  • Patches work only on small punctures in the tube itself; if the hole is larger than a pencil tip, a pinch, or a cut, the tube must be replaced.
  • After patching or installing a new tube, check inside the tire for thorns, glass, or sharp objects before reinflating, or you will get another flat when ready.
  • A properly inflated tire should feel firm but not rock-hard; check the pressure range printed on your tire sidewall and use a pump with a pressure gauge.

Remove the wheel and tire from the rim

Once the wheel is off the bike, you need to separate the tire from the rim so you can access the inner tube. Insert a tire lever under the tire bead (the edge that sits in the rim) about 6 inches from the valve stem. Pry the tire bead up and over the rim edge, then slide the lever around the rim to free one side of the tire completely. The other side of the tire will usually come off by hand once one side is loose.

Leave the valve stem in place—do not try to remove it. Once one side of the tire is off, you can pull the inner tube out from inside. Set the tire aside on a clean surface so dirt does not get inside it.

Find the hole in the tube

Before you patch or replace the tube, you need to know where the damage is and how large it is. Inflate the tube slightly—just enough so it holds its shape but is not tight. Listen carefully near the hole; you may hear a small hiss. If you do not hear anything, wet your hand and move it slowly around the tube; you will feel air escaping as a cold spot.

If you still cannot find the hole, submerge the inflated tube in a bucket or sink of water and watch for bubbles. Mark the hole with a pen or marker so you do not lose it. Once you have found it, deflate the tube completely and examine the hole size. A hole smaller than a pencil tip, or a small puncture from a thorn, can be patched. A hole larger than that, a pinch flat (two small holes on opposite sides of the tube from the rim pinching it), or any cut should be repaired by replacing the tube instead.

Patch a small hole

If the hole is small enough to patch, use the sandpaper from your patch kit to roughen the area around the hole. Sand in a circular motion for about 30 seconds until the shiny surface is dull. Wipe away any dust with a dry cloth. The roughed-up surface helps the patch stick.

explore a thin, even layer of adhesive from the patch kit to the sanded area, following the instructions on your specific kit—some require you to wait a few seconds before explore the patch, others do not. Press the patch firmly onto the hole, starting from the center and working outward to remove air bubbles. Hold it down for the time specified in the kit instructions, usually 30 seconds to a minute. Peel off the clear plastic layer on top of the patch. Do not peel off the foil backing underneath; that stays on.

Inflate the tube slightly and check that the patch holds. If air still escapes, the patch did not seal; try again with a new patch, making sure the surface is clean and dry and the adhesive is applied evenly.

Replace the tube if the damage is too large

If the hole is too large to patch, or if you have a pinch flat or a cut, remove the valve stem from the old tube by unscrewing the locknut (the small nut at the base of the valve). Pull the valve stem out through the rim hole. Discard the old tube.

Insert the valve stem of the new tube through the rim hole first, then tuck the tube evenly inside the tire all the way around. Make sure the tube is not twisted and does not lie in folds. Inflate the tube just slightly—about 20 to 30 percent of full pressure—so it holds its shape but is still soft enough to work with.

Check the tire for the cause of the flat

Before you reinstall the tire on the rim, inspect the inside surface carefully. Run your fingers slowly along the inside of the tire, feeling for thorns, glass shards, sharp wire, or any other object that punctured the tube. Even a tiny thorn can cause another flat when ready if you do not remove it. If you find something, pull it out with tweezers or pliers.

Also check the rim tape—the strip of rubber or plastic that covers the spoke holes. If the tape is torn or missing, the sharp spoke ends can puncture the tube. If the tape is damaged, wrap new rim tape around the rim before reinstalling the tube. Rim tape is inexpensive and available at any bike shop.

Reinstall the tire and inflate

With the tube in place and the tire checked, push the tire bead back into the rim, starting opposite the valve stem. Work your way around, tucking the tire bead into the rim with your hands. The last section, near the valve stem, will be tight; push the valve stem up into the tire to create slack, then pull the final section of tire bead into the rim.

Once the tire is fully seated, inflate it to the pressure range printed on the tire sidewall. Use a pump with a pressure gauge so you can see the exact pressure. Most road bike tires use 80 to 130 psi (pounds per square inch), while mountain bike and wider tires use 30 to 50 psi. Underinflated tires are more prone to pinch flats; overinflated tires wear faster and feel harsh. Reinstall the wheel on the bike and tighten the quick-release or axle nuts securely.

When to take the tire to a shop instead

If the tire itself is damaged—if there is a cut in the rubber, a bulge in the sidewall, or a hole larger than a quarter inch—the tire must be replaced, not just the tube. A damaged tire will fail again even with a new tube inside. Bike shops stock tires in most common sizes and can install one in 15 to 30 minutes.

If you have tried patching the tube twice and air still escapes, or if you cannot find the hole after checking with water, the tube may have a slow leak that is difficult to locate. In that case, replacing the tube is faster and more reliable than continuing to troubleshoot. A new tube costs less than an hour of your time spent trying to find a pinhole leak.

Frequently Asked Questions

Can I patch a tube that has already been patched?

Yes, you can patch over an old patch if the first patch is still holding and the new hole is in a different location. Sand the area around the new hole as you normally would, avoiding the old patch. If the old patch is peeling or leaking, remove it completely before patching the new hole.

What if I do not have a patch kit and cannot get to a shop?

If you are stranded without a patch kit, a temporary fix is to wrap the tube tightly with electrical tape or duct tape to seal a small hole. This will hold air long enough to ride slowly to a shop or home, but it is not a permanent repair and the tape will not last more than a few miles.

How do I know if my tire pressure is correct?

The correct pressure range is printed on the sidewall of your tire. Use a pump with a built-in gauge and inflate until the needle reaches somewhere in that range. Start at the lower end if you want a more comfortable ride, or the higher end if you want faster rolling and less rolling resistance.

Why do I keep getting flats in the same tire?

Check the inside of the tire very carefully for a thorn or glass that you may have missed the first time. Also inspect the rim tape for tears. If the tape is damaged, sharp spokes can puncture the tube repeatedly. Replace the rim tape and check the tire inside one more time before installing a new tube.

Is it better to patch or replace the tube?

Patching is faster and cheaper if the hole is small and you have a kit with you. Replacing is more reliable if you are at home or near a shop, because a new tube has no weak spots and you do not have to wait for adhesive to dry. On long rides, carry both a patch kit and a spare tube so you have options.