2torial #0707:
Learn2 Fix a Bike Flat

A tire should be round, not flat!

If you ride a bike, sooner or later you're going to have a flat tire. Perhaps you'll discover it in the comfort of home, and you'll be able to fix it at leisure in your living room, accompanied by fine stereo sound and potato chips. More likely, though, you'll find yourself on some lonely mountain trail or alongside a busy road. There'll be no music, and the sun will be rapidly sinking.

This situation calls for preparation and know-how. We'll explain what you need to carry on every bike ride and how to use it so you can get back on the road.

The truth is, you're not going to fix a flat tire; you're going to fix a flat inner tube that's inside the tire. To do this, you'll need to remove the wheel from your bicycle, and then partially remove the tire from the wheel. You'll then be able to remove the inner tube from the tire and repair or replace it. And to do this, you'll need a repair kit. Portable kits are available at most bike shops. Never take off on a long bike ride without bringing a repair kit along.

Remove the wheel

Wheels are generally attached to the bike frame through one of two mechanisms--the standard nut or the quick-release mechanism. Here's how to use both:

• If your bike has standard nuts holding the wheel on, use the wrench to turn each nut counterclockwise. Alternate between the two nuts until both are loose, but not removed from the wheel. There may be a metal security device, which you'll need to pull away from the slots in the bike frame where the wheel's hub is attached. You need to release these before you can free the wheel.

• If you have a quick-release mechanism, just grip the lever and pull the end away from the wheel to loosen it. Now hold the other side of the wheel steady, and turn the lever counterclockwise a few times to loosen it a bit more.

Once the wheel is ready to drop out of the frame, you'll also need to open the brakes wide enough to let the tire pass through. Many bikes have some sort of quick-release mechanism just above the brake pads to help you do this. It often looks like a small lever, and sometimes takes the form of a metal tube seated horizontally inside a rubber boot. If yours has neither, you should still be able to squeeze the brake pads close to the wheel, and then pull one end of the brake cable free of the metal arm. You'll know you've done it right when the brakes open much wider than usual.

If you're removing the rear wheel of a multi-speed bike, shift the gears until the chain is sitting on the largest cog on the chain ring near the pedals and the smallest cog (the one farthest from the wheel itself) on the rear wheel. This will allow for easier removal and replacement of the rear wheel.

Partially remove the tire and the inner tube

The reinforced edges of a tire that press against the inner walls of the wheel rim are called beads. There are two beads per tire, one on either side, and to get to the inner tube you'll need to detach one of them from the rim and reach underneath it. To do this, you'll need to use the tire irons to lever the bead over the rim without pinching the inner tube.

First release any remaining air from the inner tube. Air is released (and injected) by means of the metal valve on the tube. The most common kind of valve is called a Schraeder valve, which works by pressing on the metal piece in the center. A Presta valve is tall and skinny, also with a metal piece in the center. To release air, you must unscrew the collar from around the base of this piece. Then press down to release air. Most bike pumps have fittings for both types of valve.

Once the tube has been emptied, choose the side of the tire you want to work from. If you're working on a rear tire, you may want to choose the side away from the gear cluster, which can be greasy. Squeeze this side of the tire so it pulls away from the rim's edge and moves toward the rim's center well. The bead won't stay in the center well, but this process will loosen it from the rim's wall, where it can become entrenched. Keep shifting your grip and squeezing until you work your way around the entire tire.

Insert the curved end of the tire iron under one bead, near the valve. Look to make sure the inner tube isn't pinched between the bead and the iron, and then lever the bead over the rim and hook the iron onto a spoke of the wheel. (There's a slot in the iron designed to hook onto the spoke.)

Next, take a second tire iron and repeat the same action, beginning on the other side of the valve, two or three spokes away. Take the third tire iron and repeat the action once more, again starting two or three spokes farther along. At this point, a tire iron may fall out, as you've leveraged a significant section of the tire bead off the rim. That's OK. Just use the loose tire iron to remove the rest of the tire's bead off the rim. Be careful not to catch or pinch the tube while doing this.

If a tire iron hasn't fallen out, just use one of the outside irons to continue peeling the tire bead away from the rim in a kind of skimming motion with the curved end leveraged underneath the bead. You can also use your fingers at this point. The bead you're working on should be completely off of the rim when you're finished.

Find the hole

Carefully pull the inner tube out from under the tire. You should be able to push a Schraeder valve through the hole in the wheel rim to remove the tube, but you'll have to unscrew a small metal retaining collar if you have a Presta valve setup. Try not to bend the valve when you pull out the tube. If you plan to replace the damaged tube with a new tube, skip to Step 5.

If you're going to patch the tube, you'll have to find the hole. Repairing a tube is cheaper than replacing it, but sometimes the damage is too severe. In these cases, or if the problem turns out to be a previous patch that has failed, your best bet is to replace the tube.

After removing the tube, use the pump to inflate it. Examine the full tube carefully--you might get lucky and spot the problem. But if the puncture isn't obvious, hold the tube close to your ear and slowly rotate it as you listen for the hiss of air escaping. If you're at home, you can submerge part of the tube in a shallow pan of water and rotate it slowly (you'll be able to find the puncture by watching for air bubbles).

If you still can't find a puncture, check the valve's condition. If it's cracked or severely worn, you'll have to replace the tube.

Patch the inner tube

You can find various patch kits where bicycles are sold. They basically consist of small pieces of rubber that you can stick over the damaged inner tube with glue. Some kits provide rubber pieces already coated with adhesive for faster repairs, while others contain a separate tube of glue. Make sure the kit you buy contains a scraper or some sandpaper to initially roughen the inner tube's surface for better holding power. Refer to the directions on your patch kit; most will be a variation of the following:

• Clean and dry the damaged area. Use water from your bottle, or saliva if you have to.

• Lightly roughen the damaged area with sandpaper or a scraper to help the patch adhere properly.

• If the patch doesn't self-adhere, apply a thin layer of glue over the hole. Try not to spread it beyond the area to be patched. Let it dry until it becomes tacky to the touch.

• Place the patch onto the area, and hold it firmly in place so it bonds with the tube.

• After the patch has set, which takes about two minutes, inflate the tube to make sure the patch is holding properly. Don't overinflate it, though; an inner tube can blow up like a balloon without the surrounding tire to keep it contained.

Determine the cause

Before you reassemble everything, you should inspect the tire to find out what caused the hole in the tube. Sometimes you won't be able to find anything, but often the culprit is still lodged in the tire, ready to cause another flat.

You may be able to find the problem by lining up the valve stem and the valve hole in the rim, then finding the spot on the tire that corresponds to the puncture in the inner tube. If you can't find the damage this way, look closely at the tire. Search for sharp objects embedded in the outside, checking any debris that's caught in the tread. If you still don't find anything, inspect the inside of the tire. You can use your fingers, but proceed gingerly so you don't hurt yourself. Most punctures come from thorns, tacks, or small bits of glass.

If the tire has a larger tear in it, you can use a folded dollar bill to "boot" the tire, that is, act as a protective layer between the tube and the gash until you get home.

If you don't find anything in the tire, inspect the well area. The ends of the spokes should all be covered with a strip of material that protects the inner tube. Sometimes a spoke will poke through the strip, or the strip may shift aside. A damaged strip must be replaced, but you can make a (very) temporary repair with a patch and glue from your repair kit, or you can boot this area with a folded dollar bill.

Remount the tube

Whether you're inserting a patched tube or a new one, the most important thing is to make sure it sits properly inside the tire.

To properly reinsert an inner tube, release most of the air, until it's limp but not flat. If you're replacing the old tube with a new one, pump just a little air into it to attain the same effect. If you have it, sprinkle a little talcum powder around the tube. This will help it seat properly inside the tire.

Insert the valve into the hole in the wheel rim, and tuck the rest of the tube under the tire. Check as you go to see that the tube doesn't stretch or twist. Make sure the valve sits straight through the hole (and not at an angle) when you're done.

Replace the tire on the rim

Getting the tire back onto the rim without damaging the tube can be a bit tricky. The safest way to do it is by using your hands. Use a tire iron only if you absolutely have to.

Starting at the valve, begin to slip the tire bead back over the rim with your fingers. If you push the bead into the center well, you'll create a bit more slack in the tire and make your task easier. Continue working in one direction around the wheel, until the bead is almost completely reseated. Take your time, and make sure the tube doesn't get pinched between the rim and the tire.

When only 2 to 3 inches (5 to 7.5 centimeters) of unseated tire remain, wrap your fingers around the tire and grasp the remaining bead. Firmly push the last of the bead back over the top of the rim until it seats inside. You may have to use your palms or, as a last resort, a tire iron to get this last section back on the rim.

Push the valve partially back into the hole. This will help the tube seat properly. Pull the valve back out, and make sure it's sticking straight out from the rim. You can adjust an angled valve by grasping the tire and tugging it along the rim until the valve is straight.

Once the tire is on, squeeze its sides and check it to make sure no part of the tube is caught between it and the rim. Then partially inflate the tube, and make one last visual check. Make sure it's inflating evenly, and that no portion of the tube is visible. Fully inflate the tube and replace the valve cap.

Remount the wheel

This procedure will vary depending on the type of mechanism that holds the wheel onto the frame. You're really just reversing the process of wheel removal in Step 1.

Holding the wheel steady with one hand and the bike frame with the other, guide the wheel back through the wheel mounts and the brake pads, and seat the hub back into the hub slots. If you're working with a rear wheel on a multi-speed bike, be sure to settle the bike chain back onto the sprocket cluster, so the chain seats properly. To do this easily, engage the chain with the outside, smallest cog on the sprocket cluster, which you shifted to before removing the wheel.

Before tightening the hub assembly, make sure the wheel is positioned properly within the frame. There should be equal space between the tire and the frame on either side. Sometimes the brake pads are helpful in centering the tire. You should check the pads anyway, to make sure nothing is off-center, and the pads won't be rubbing against the wheel when the brakes are reset.

Secure the wheel hub, either by closing the quick release lever or by using a wrench to tighten the nuts. If you're working with nuts, partially tighten both before firmly tightening either one.

Last, return your brake pads to their normal position. If you have a quick release lever, just flip it back down, or reseat the metal tube within the rubber boot. If you've detached the brake cable, firmly pull the end back into the metal arm.

The most satisfying conclusion to a flat repair is to get on your bike and ride away. Don't forget to pick up your tools, though, because someday you may need them--and your new repair skills--again!

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