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How to fix a flat: Repair and rejoice (part 2)
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Prevention and preparation (Part 1)
To repair a flat, you will need an air pump, a tire lever (also called “tire iron” though it is made of plastic), and a patch kit or new tube. You may also need a crescent wrench. These are small enough to fit in a economical tool pouch (about the size of a makeup bag or fannypack), and possession of them at all times will save you a ton of grief and frustration.
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Photo courtesy of jimlangley.net
Turn bicycle upside down to make it easier. Determine if it is the front or rear wheel that needs repair. If the bicycle has hand brakes, release them by squeezing them together on the rim, and unhooking the brake cable from the pad. This will make it easier to remove the wheel. If your bicycle has a derailleur, shift into the smallest cog before removing the wheel.
If your bicycle has a quick-release, it should be on the left side of the bike. It is a mechanism with a handle and a skewer that goes through the wheel and attaches to a nut on the other side. Most levers are marked “open” or “closed.” While riding, the lever should be closed. Opening or closing requires flipping it 180 degrees like a hinge, not spinning it. The quick-release is also curved, so if it is closed, the bump will be on the outside. If open, the lever will appear cupped. Spinning the quick release counterclockwise while it is open will loosen the nut.
If your bicycle does not have a quick release, use a crescent wrench to unscrew the nuts on either side of wheel. They do not have to be removed completely, only loosened to the point that the wheel comes off easily. Do not use pliers; they will damage the nuts so that the proper wrench will not fit, and they will not sufficiently tighten the nuts when putting the tire back on.
Deflate the tube completely. A Schrader valve on a tube is a spring-loaded valve inside a cylindrical metal tube, and is used on low-end bicycles, bikes with large tires, and automobiles. It has a screw-on cap and a metal pin inside that, when compressed, releases air from the tube. A Presta valve is smaller and has a small nut to keep the core tight. To deflate, unscrew the nut a little and press down.
Left: Schrader valve, Right: Presta valve; photos from Wikipedia
Check to see if there are any obvious signs of protrusion, such as a nail or piece of glass sticking out of the outside of the tire. If you find any, remove them. Use the tire lever to pry the lip of the tire over the rim on one side of the wheel. Start away from the valve, lest you tear a hole at the base of the valve where it connects to the tube. Removing the entire tire is unnecessary. Take out the tube once done, keeping track of which side it was facing in the wheel.
Run your fingers slowly and carefully in the inside of the tire; thoroughly check for debris or other sources of the flat. Check both the tire casing and the inside of the rim. If you find one or more, remove them. You don't want the fresh tube to puncture as soon as you get it back in the wheel. Location of such an item will also help you determine where the leak on the tube is.
Conversely, finding the leak in the tube may assist in finding the source of the puncture. Once the tube is out, fill it with air and squeeze. A hissing noise will alert you as to where the hole is. In cases of extreme doubt, immersing the air-filled tube in water will locate the hole by the bubbles coming out. Usually this step is not necessary, and a hindrance if you plan on patching the tube. Using the location of the hole as a reference, return to the tire casing once again and see if there is any remaining debris.
Decide if you want to patch the tube or replace it completely. I usually opt for a new tube to keep peace of mind. However, patching is also a reliable option, and not everyone keeps a spare tube handy. If the hole is a puncture, it will patch easily; if it is a long tear, it will not patch and the tube should be replaced. When using a fresh tube, you may want to stretch it a little by hand
If you do replace the tube but the hole is minor, patch it anyway if you have the time and keep it as a spare--or a freebie to a poor hapless soul on the road who didn't think ahead to bring a replacement tube of his own.
To patch, select one that is the appropriate size. Make sure the tube is completely dry and emptied of air once again. Take the sandpaper provided in the patch kit and buff the puncture in an area that is larger than the patch itself. Insufficient buffing will cause the patch to fail. Good buffing helps the glue bond. Avoid touching the buffed area. Apply a dab of glue and spread it in a thin coat over an area that is, again, larger than the patch itself. Let it dry completely. Completely. Applying a patch while the glue is still wet will also cause the patch to fail.
When the glue is totally dry, peel the foil from the patch and stick the patch on the tube over the glue. Apply firm pressure for at least 60 seconds. Some prefer to stand on the patch. Sing as much as you can remember from “Bohemian Rhapsody” or “American Pie” while waiting, if it helps. If you choose this method, you might also want to put your hat on the ground, as passersby may wish to toss coins in it. After a minute or two, peel back the plastic covering. If the patch remains in place while removing the plastic, you have done a successful job. If not, retrace your steps and try again. Make sure it is sealed all the way around the patch, otherwise the hole will leak.
Line up the valve with the valve hole in the rim, and insert the tube back into the tire. Tuck the tire lip back into the rim using a tire lever or your hands. Make sure it is on evenly and that no part is pinched between the tire and rim. Re-inflate the tire to the proper pressure. Some choose to re-inflate just a little, deflate again, and then fill completely, just to make sure the tube is evenly distributed around the tire.
Put the tire back on the wheel. When tightening the nuts, alternate tightening both sides. Make sure the chain is on properly if applicable. Turn the quick release in “open” clockwise to tighten, positioning the bike as if you were riding it. Close it when it is tight. Doing so will prevent the wheel falling out while you are riding. Remember to re-connect the brakes. Start out slowly, paying attention to any differences or telltale signs while riding.
Rejoice, for you have acquired a desirable and incredibly necessary skill. Good work!
Helpful related sites: www.sheldonbrown.com
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