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Flat Tire Repair

You're thinking, "Who needs to be taught how to fix a flat tire?" Well, everybody. We all have to start somewhere.

If you get extremely frequent flats, see the options in our tire care section.

Of course, we're assuming you have a pump and patch kit with you. (And a spare tube, of course.) If not, start walking.

First step: If the rock or thorn didn't let all the air out of your tire, let the rest of the air out now.

Release the brake cable.

On a cantilever (cable-pull) brake, push the cable down while holding the brake lever in against the tire. When the barrel comes loose, slide the cable away from the lever.

On V-brakes, squeeze the two brake levers towards each other, then pop the cable guide up out of the retainer.

bf-tir2.jpg (11681 bytes)

bf-tir3.jpg (9047 bytes) Take the wheel off. To remove the front wheel, pop the quick-release down, then unscrew the nut on the opposite side until the wheel can fall out of the fork.

To remove the rear tire, shift the rear deraileur until the chain is in the smallest ring of your cassette (highest-numbered gear). Turn the bike upside down, then open the quick-release lever. Pull the wheel forward off the chain, moving the opposite side of the chain out of the way as the tire comes up.

Remove the tire casing from the rim by squeezing it in, all the way around the tire. Position the two sides of the bead together, in the little valley in the center of the rim.

Pull one side of the tire up, making sure the opposite side lies in the valley in the rim's center. Slide the tire lever down between the rim and the tire about 1/4 inch. Pull the lever down, exposing the bead of the tire.

Trap the exposed bead of the tire with your thumb.

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Now move the tire lever away from your thumb. Take care that it isn't too far inside the tire casing -- you could cut the tube. If the lever seems to hang up, it may be caught on the tube.

Run the tire lever around the entire rim. Leave the opposite side of the tire on the rim while you pull the tube out of the casing.

If the tire is too tight, you may need to use two (or even three) tire levers to work the casing off the rim.

Tire levers have a notch that holds onto the spoke, so you can pry the tire bead out and hook the lever, then have hands free to go on to the next spot on the rim.

tireleak.jpg (8609 bytes) Now the hardest part: pump the tube up and find the leak. A leak that flats your tire while riding can usually be detected by running your ungloved hand around the full-pumped tube and feeling for the flow of air. If a leak is rapid enough to flatten the tire while riding, you'll probably be able to feel or hear the escape of air.

For slow leaks, you may need to dunk the tube underwater and look for the bubbles.

Buff the tube.

Use sandpaper (preferred for bike tubes) or a patch-kit scraping tool to buff the tube. This is one of the most important steps. You must remove all oil, moisture, dirt, and talc. You must scuff the smooth tube surface so the glue can penetrate. Buff an area 1/4 inch bigger on each side than your patch.

If the hole is near a seam on the tube, spend extra time buffing the seam flat.

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bf-tir7.jpg (9178 bytes) Spread the glue.

Use only fresh, runny patch glue. If the adhesive has gotten old and gelled, the patch may not stick once the tire is inflated. Spread a thin coat of adhesive over the entire buffed area. Don't leave any deep spots. Let the glue dry for a couple of minutes.

While the glue is drying, run your fingers around the inside of the tire casing. Remove any rocks and dirt. Feel for a thorn. If you can't find the cause of the flat, inspect the outside of the tire. Sometimes a thorn will appear as a small brown dot in the tire tread.

If the cut is on the inner curve of the tube, it may have been damaged by the spoke holes. Check your rim tape to see if there are any exposed edges.

bf-tir8.jpg (11204 bytes)

tirethrn.jpg (8044 bytes) See the tiny spike sticking up from the inside of the tire casing? This thorn could be felt, but couldn't be seen during routine inspection. Be sure you're very thorough -- if you can't find an obvious puncture, match the valvestem of the tube to the valve hole in the rim, see where the puncture would fall on the tire, and doublecheck that area!
Test to see if the glue is dry by touching a spot ON THE EDGE of the repair area. Don't touch where the patch will be.

The adhesive should be barely tacky. It shouldn't string or hold your finger.

bf-tir9.jpg (6460 bytes)

bf-tir10.jpg (6588 bytes) Prepare the patch.

If it's just a puncture, a standard 3/4-inch patch will do. If you have a slice, you'll need a patch at least 1-1/2 inch long. In general any slice longer than 1/4 inch won't hold a repair.

Peel the blue side away from the patch, holding a tiny corner of the patch with your fingernails. DON'T touch the rubber surface.

Apply the patch.

Press the patch very firmly into place. Squeeze at multiple locations to be sure all parts of the patch are firmly bonded.

If you have talc available, spread some over the exposed adhesive. If not, powdery dirt will do. This keeps the tube from bonding to the tire casing.

bf-tir12.jpg (7630 bytes)

tube03.jpg (13688 bytes) A press-on patch, such as those shown in this photo, can save you the trouble of applying cement, but the tire still has to be buffed. These patches can work well for tiny punctures. But if tire pressure is low when riding in rough territory, the patches may come loose.
Replace the tube in the casing. Be sure the valve stem is straight in its hole. Turn the tire so the valve is at the bottom.

Starting at the valve-stem, push the casing under the rim. Move both hands simultaneously around the rim, seating the tire. When you reach the top, push the tire away from you to pull the last part of the bead over the rim. If the tire is tight, put two tire wrenches under the bead and gently lever the tire over the rim as shown.

tireback.jpg (11326 bytes)

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Pump up the tire and check it. Put it back where you found it, and be sure to reattach the brake cable!

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