Fixing a Flat Tire

First, here’s some general information about tires:

Since tires are your only contact with the road, it’s important to make sure they’re in good working order. Inspect them regularly for cuts on the tread or sidewall. Small cuts can hold shards of glass or thorns, which can eventually cause a flat tire. Big gashes can allow an inner tube to ooze through. Nothing’s as frightening as having a front tire blow out while you’re blasting downhill. The rear tire will wear faster than the front tire, since it bears more weight and is the driving wheel, so watch it carefully.

Inflation pressure is also important. Proper pressure keeps the rolling resistance of the tire low and helps avoid flat tires caused from rolling over uneven surfaces. The recommended inflation pressure is printed on the sidewall of the tire.

Use a hand bicycle pump or a floor pump to inflate your tires. Most floor pumps have gauges built into them. If you use a hand pump, use a gauge to verify the pressure. Check your tires before each ride.

Tires that have never been used can still go bad. They dry out and lose their elasticity, so they crack and puncture easily. Replace your tires annually. It’s a cheap investment.

Fixing the flat:

To fix a flat, you’ll need a few tools: tire irons, a patch kit, a pump, and some arm muscles. (See, cycling [b]is[/b] good for upper body strength.)

The first thing to do is to remove the wheel from the bicycle. If it’s the front wheel, it’s a cinch – release the quick release and remove the wheel. The rear wheel is ornery because you have to contend with the chain and the rear derailleur. Before removing the wheel, shift the chain until it’s on the small sprocket on the back and the small chainring on the front. Then loosen the quick release and slide the wheel out. If the rear derailleur cage holds things back, just pull the cage gently downward and rearward to get it out of the way.

The next big project is to remove the tire from the rim of the bicycle wheel. You’ll probably need a set of tire irons to do this. Sometimes, if the fit is loose enough, you can work the tire off with your hands, but you’ll usually need tire irons. Start on one side of the tire and work it off the rim, using the tire irons to gently pry it over the rim. Be very careful not to crimp the inner tube in the process. Once this side is off, you can reach in and remove the inner tube. Make sure you take off the plastic valve cap and the small nut on the inner tube valve before removing the tube. Now, remove the other half of the tire.

If you watch others fix a flat, you may notice they don’t take things apart as completely as you are. You can get away with less, like just pulling out the tube where it’s punctured if you want to repair it and you know where the puncture is. The point of this exercise is to learn about the makeup of a wheel, so that’s why you’re now holding an inner tube (punctured), a tire (punctured or possibly worse), a wheel, and maybe a rim strip (wondering what the heck it is and where it came from).

The rim strip is a strip of plain rubber or adhesive backed cotton that wraps around the rim to protect the inner tube from the sharp edges of the rim where it’s drilled for the spokes. Adhesive backed cotton strips are preferable because they don’t migrate and they have a very long life. Rubber strips can move around and eventually dry out. Make sure the rim strips fully cover all of the spoke holes, or this could cause future flats.

You have two options now: you can repair the damaged tube (see the instructions that came with your patch kit), or you can use the spare inner tube you always carry with you. Regardless, make sure the culprit that caused this flat isn’t still with you. Start with the tire. Check it inside and out for a tack, shard of glass, whatever. If something’s still embedded in the tire or floating around in the casing, you may have another flat in avery short time. Try to find the damaged area. If it’s small, you can usually ignore it. But if it’s large enough for more debris to enter, you should patch the inside of the tire.

It’s a good idea to look at the tube, too. It can give you a lot of information. Flats aren’t always caused by events on the outside. They can be caused by aliens on the inside. For instance, if the rim strip has moved out of place, a rough spot on the rim may rub against the inner tube and eventually puncture it. If the puncture is on the outer circumference of the inner tube, the culprit came from the outside; if the puncture is on the inner circumference, it came from within the rim. In any event, make sure you know what the cause is so you can finish your ride without more problems.

Reassembly can be a breeze or a bear. Start by making sure the rim strip is on and straight. Then put one side of the tire back on the rim. Put the inner tube back in, starting with the valve and then work the entire tube back in place. (Sometimes it helps to keep the tube slightly inflated, but let all of the air out after the tube is in place.) Keep it straight and untangled. Here comes the breeze or bear part: starting at the valve, using your thumbs, begin working the last side of the tire onto the rim. Check the valve occasionally to make sure it points straight toward the center of the hub. Also make sure the tire bead is seated in the rim at the valve. If you push the valve back into the tire, it will make room for the tire to “seat” itself properly.

By the time you get about half way around the rim, it’s going to get harder to slip the tire on the rim. Make sure the tube is completely deflated and work the tire opposite the hard spot down into the channel of the rim to give you as much “slack” as possible.

It will be very tempting to use a tire iron to pry the tire back on, but you really shouldn’t because this will inevitably pinch and puncture the tube. If you must use a tool, use one like the Crank Brothers Speed Lever. With this tool, you can pry the tire onto the rim without hurting the tube. The best situation is to use your hands, but sometimes you can encounter a very difficult fit–the rim is just a little too large and the tire is just a little too small and the result is misery and frustration. Be patient. People have been known to flag down passersby on the theory that two pairs of thumbs are better than one.

Don’t use a gas station air hose to inflate your bicycle tires–the air goes into the tube so quickly that it can blow out the inner tube–car tires have much more volume than bicycle tires. Ever try to inflate a car tire with a bicycle pump?

No pump? Take out the inner tube and stuff the tire casing with leaves, grass, or newspaper. Ride very slowly and walk all your turns! Hole in the tube too big and you have no spare? Cut the tube in two, tie a knot at each end, reinstall and inflate at a low pressure. Tire casing gashed? Use a dollar bill, duct tape, or an old tire casing to make a boot.

Practice makes perfect, so you may want to try taking the tire and tube off your wheel and reassembling it. Better to learn about the snags in the privacy of your own home than under duress in a rainstorm!

Tailwinds,