Fixing a flat tire on a bike

If your bike gets a flat tire, don’t automatically assume it’s punctured, especially if the leak is slow. Check the tire’s valve first. Simply turn the wheel so that the valve is on top, remove the valve cap, and submerge the entire valve in a glass of water. If bubbles form, re place the valve core. Use valve caps with valve-removing prongs to unscrew the old core. (Certain needle nose pliers will also do the job.)

If you find a cut or hole in the tire, mark it with chalk to make it easier to find the corresponding place on the tube. Pull out any nails with pliers and pry out glass with a screwdriver. To get to the tube, you will probably have to remove the wheel. Follow the directions in your owner’s manual. Finding the leak

Completely deflate the tire. Use a spoon handle (a screwdriver is too sharp) to pry a small section of the tire from the rim. Leave the spoon in place and run a second spoon handle all around the rim to free the tire on one side. Leaving the valve in place, carefully work the rest of the inner tube out of the tire. Inflate the tube and run your hand around it to find the air flow. Once found, mark the spot with chalk. Check the corresponding place on the tire for nails, glass, thorns, or other sharp objects and remove them.

If you fail to find the leak, remove the valve-holding nut, if any, and push the valve stem out of the wheel rim. Partially pump up the tube and pass it a little at a time through a bucket of water, stretching the tube a bit as you do. Bubbles will form over the puncture. Mark the puncture.

Deflate the tube again. Using the materials in a patching kit (available at bike shops), sand the area clean, then apply a light, even coat of adhesive to the cleaned area and let it dry.

Peel the backing from a patch and press the patch, sticky side down, onto the adhesive on the tube. Press down firmly on the edges of the patch with the bowl of a spoon and let the adhesive dry for 5 minutes. Push the tube back into the tire, inserting the valve through its hole in the rim. Reseat the tire with your hands, checking that both edges are inside the rim. Replace the valve-holding nut, if any, and inflate the tire to the proper pressure (usually listed on the sidewall of the tire).