Its Easy to Fix a Flat

It's Easy to Fix a Flat

BY JIM LANGLEY

Sooner or later, it will happen. You'll be pedaling merrily along when you hear hissing or a sudden kapow, and one end of the bike will sink. Yep, it's a flat tire, by far the most common breakdown you'll face as a cyclist. Worry not. The repair is simple.

To guarantee that you'll laugh away your next flat, here's a step-by-step tube-replacement guide. Make a copy to keep in your seatbag with your repair kit. You won't need instructions after you've done the procedure a few times.

Handy Helper

I'll assume that you've flatted while riding. If you're working at home and have access to a floor pump and a repair stand, by all means use them. On the road, it's not necessary to support the bike, but you may be able to by hooking the nose of the saddle over a fence or low branch. Or ask a riding partner to hold the bike while you operate.

1. Open the brake. To make it easy to remove the wheel and put it back in, most brakes can be widened. For a cantilever brake, squeeze both brake pads against the rim with one hand and unhook the transverse cable from the brake arm (see photo). That's the short cable that passes over the wheel to join the two arms. For sidepulls, look for a small lever on the caliper or brake lever and open it to spread the pads (see photo). For parallel-pull brakes (such as the
Shimano V-Brakes found on many mountain bikes), squeeze the pads against the rim with one hand and pull the noodle (the L-shaped piece of tubing that the cable passes through) out of its holder in the brake arm, which will allow the brake to open.

2. Remove the wheel. Most bikes have quick-release (QR) hubs so wheels can be removed without tools. If it's a rear flat, first hand-shift onto the smallest cog to move the derailleur fully to the outside. Next, open the QR by flipping the lever 180 degrees. You should feel it loosen, and you may see the word "open" on the lever. It helps to pull the derailleur back with one hand as you push the wheel forward and down with the other (see photo). That's all it takes to remove the wheel. Then, support the bike on something or lay it on its left side so the drivetrain won't be against the ground (you don't want sand in your chain). Front wheels won't necessarily come off when the QR is opened. Many bikes have nubs on the fork dropouts that capture the QR to prevent the wheel from dislodging if the lever is improperly tightened. If this is your setup, hold either end of the QR and unscrew the other until it clears the nubs. Then remove the wheel.

3. Remove the old tube. If any air remains, deflate the tube completely. Depress a Schrader valve (which resembles a car-tire valve) with the corner of a tire lever; unscrew and depress the top of a presta valve. Then hold the wheel upright and slide a tire lever under one edge of the tire (the "bead") on the opposite side of the wheel from the valve stem. Pull the lever down to pry the bead over the rim, and hold the lever or hook it to a spoke. Place the second lever under the same bead, about 4 inches from the first lever, and pull it down, too (see photo). Repeat the process, leapfrogging the levers. Soon, a section of the bead will be off, and you should be able to slide a lever around the rim to free that entire side of the tire. Then reach inside and extract the tube.

Note: A presta valve may be held through the rim by a nut or knurled ring, which must be unscrewed before the tube can be removed.

4. Install a new tube. The easiest way to fix a flat during a ride is to replace the tube. Save the punctured one to patch at home, then make it your spare. Before installing a fresh tube, you must check the tire to see if whatever caused the flat is still sticking through. Gingerly feel all the way around the inside circumference. If you have a rag, wad it and slide it in both directions (see photo). It will catch on anything sharp. If you find something, carefully pick it out with a fingernail or poke it out with your minitool. Next, inflate the fresh tube just enough to unflatten it and remove any wrinkles. Put the valve stem through the hole, then feed the tube into the tire. If necessary, let some air out so the tube fits without folds.

5. Attach the tire. Start at the valve stem and work with both hands in each direction to push the loose edge of the tire over the rim. You'll wind up on the side opposite the stem with several inches still to go. This last section can be tough to get on, especially for skinny road-bike tires. If you have a problem, go back to the stem and fully deflate the tube. Also, wiggle the valve stem and push it up into the tire to make sure the tube isn't caught under the beads. Pinch the two beads of the tire together so they fit into the deep center portion of the rim, and continue doing this as you work your way around to the obstinate section. Place the wheel on your knee, hold one end of the uninstalled section to keep it in place, then use your thumbs or the heel of your stronger hand to roll the bead up and over (see photo). Resist using tire levers, because there's danger of pinching a hole in the tube. After the tire is mounted, go back to the valve stem and push it up into the tire again to make sure the tube isn't caught under the beads, then pull it down.

6. Inflate the tire. Place the pump on the valve. Grasp the head and brace it by wrapping your thumb over the tire and your finger behind a spoke so you won't bend or break the valve stem when pumping forcefully (see photo). Inflate to half-pressure, then check for proper seating. A fine line molded into the tire sidewall (called the bead line) should appear just above the rim and be equidistant from it all the way around on both sides. Spin the wheel to eye this. If the line bows above the rim, it means the tube is caught under the bead and will blow out if you keep pumping. Deflate the tire and wiggle this section to get the tube inside the tire. Sometimes you may have to carefully poke the tube with a tire lever. If the bead line dips below the rim, keep pumping and it should pop up.

7. Install the wheel. For a front wheel, stand the bike up and center the wheel in the fork with the quick-release (QR) lever on the bike's left side. Make sure the wheel's axle is fully inserted in the dropouts. If you had to unscrew the QR to bypass dropout nubs, hold the lever open and turn the nut clockwise. The adjustment is correct when the QR begins to clamp after you've closed the lever about halfway (see photo). The force required to finish should be enough to leave an impression on your palm, and the lever should wind up tucked next to the fork blade. The procedure is similar for the rear wheel, but clamping the QR should be as easy as flipping the lever because you didn't need to change its adjustment. When installing a rear wheel, remember to set the chain on the smallest cog, where it was when you removed the wheel. Make sure the tire is centered between the chainstays behind the bottom bracket and the seatstays by the brake. Close the QR so that the lever ends up between the left chainstay and seatstay, where it can't be loosened accidentally. Finish the job by hooking up the brake cable or by closing the brake QR.

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