C-Sig Training Series

CHANGING A REAR TIRE

1. Shift rear gears into the highest cog (farthest from the bike frame) and front gears into the middle (if triple chain) or lowest (if double) chain.
2. Open the brake release (do not unscrew it).
3. Stand facing the bike from the rear and spin the wheel forward. Does it wobble or is it true? Is the frame bent? Look at the wheel's position relative to the seat stay; is it centered? Look at the wheel position from brake axle to wheel and from between the chain stay. This will give you an idea of the wheel's placement after the flat is fixed and the wheel is put back on the frame.
4. Open the quick release. While pressing down on the rear derailleur, rap the tire. The wheel should drop out. NOTE: some bikes have a precautionary lip to help hold the wheel on the dropouts; lift the wheel up and forward over this lip to free it. (Look at the dropout. Is metal still sharp or does it look chewed up? If the latter, let your bike mechanic know about it.)
5. Lay the bike down, gear side facing up.
6. Holding the tire with both hands, break the rim lip seal by pressing the tire away from the rim. Do this all around the tire's circumference. The idea is to force the edge, or bead, of the tire wall off the rim and into the well.
7. Starting about 4 inches from the valve, insert the smooth end of the tire iron under the tire's edge and lever the edge up. Hook the other end of the iron on the nearest spoke. Moving away from the valve another 2 inches, insert a second tire iron under the tire's edge. Try to lift it up and over the wheel rim. If the tire is tight in the rim, use a third iron, 2 inches away from the second tire iron. The middle tire iron will drop off. Use the smooth edge of this iron to lever the edge over the rim, working your way all around the wheel until one side of the tire is off.
8. Use one hand to push the tire aside and feel for the tube. Pull the tube out, starting away from the valve and on the wheel side opposite that of the gears. Remove the valve last, and note the position of the tube relative to the tire. Most bike shops mount the tire so that the tire pressure information is centered just above the valve hole.
9. Pump some air in the tube and look for punctures. To feel the pressure of escaping air, put the tube under your nose, chin or eyes. Make sure all punctures are found.
10. Line up the tube to the tire's original placement, and check the outside of the tire for intrusive objects like nails or glass. With 3 fingers, slowly and carefully inspect the inside of the tire for sharp objects and remove them. Once the object is removed, if the puncture disappears the tire is probably okay. But large, visible punctures should be patched with a boot (about $1. in bike shops). A plastic candy wrapper or dollar bill can also work; they keep the tube from pushing into the puncture when the tire is fully pressurized.
11. Sharp objects implanted in the tire are not the only reasons for flats. Two nearby holes in the tube, called snakebite, can result from incorrect tube placement or low tire pressure, causing the tube to be pinched between the tire and the rim. The latter happens when the bike hits a big bump and the tires are under inflated.
12. Also check the rim and rim tape. The tape provides a smooth cover over the spoke holes for the tube to sit on. The best rim tape is cloth, but many bikes come with hard plastic rim tape. If torn, its sharp edges can puncture the tube. So check the rim tape carefully for smoothness, protruding spoke ends or uncovered rim holes. If present, they can be temporarily patched using part of a tire boot. Then see that the condition is corrected as soon as possible after the ride.
13. Hot weather can contribute to flats, as well. A rise in temperature causes air to expand, and if the tire pressure is too high, the tube may burst.
14. If it is necessary to patch the tube while on a ride, follow the directions on the patch kit. This involves sandpapering the area around the puncture so glue can adhere. If the puncture is at the bottom of the tube, also sandpaper out the tube's ridge. (Otherwise, after inflating the tube, the ridge can allow air to escape from under the patch.) Rub the glue into the tube, using a circular motion, then wait at least one minute for the glue to get tacky and begin to set. Don t rush this step or the patch may not hold properly and could cause another flat, Now apply the adhesive patch over the puncture. There will probably be some excess glue around the patch; rub a little road dirt on it so that it s no longer sticky.If the tire was completely removed from the rim, replace one side of the tire on the rim. If the thread has directional markings, install the tire with the markings headed in the same direction as the wheel s rotation (forward). Position the tire on the rim so that the tire pressure information is located above the valve hole.
15. Lay the wheel on the ground. Pump a little air in the tube so it is no longer flat. (Clinch refers to putting a new tube on without partially inflating it first, so it adheres between the tire and rim.) Insert the valve through the rim hole so that it points straight down. Now work the rest of the tube onto the rim, tucking it under the tire and making sure it doesn t get twisted or pulled. Inflate the tire a little more fully and, with your fingers, quickly check that the tube lies correctly under the tire and on the rim.
16. Now put the other tire bead on the rim, starting from the valve position. Using both hands, work simultaneously away from the valve. This requires some degree of hand strength. Work carefully, short portions at a time. The final portion of the tire to be seated on the rim will be the hardest. To make it easier, go back to the valve location and with a hand on either side, begin massaging and stretching the tire, pushing it into the rim and pulling down away from the valve to the last portion to be seated. You can also try taking some air out of the tube. Some new tires, or ones like Kevlar beaded, may be so tight that you will have to use a tire iron to get the last part of the bead over and on to the rim. Use caution, as a tire iron can pinch (puncture) the tube during this maneuver.
17. Before fully inflating the tube, push the valve up into the tire and pull it back down firmly. This ensures that the tube is seated correctly between the tire and rim.
18. Holding the wheel s hub on either side with both hands, spin the tire and look at the tire line. It should be evenly placed just above the wheel rim. If this thin ridge line is farther from the rim in one place, it will probably be under the rim on the opposite side. Rework the tire so that the line is evenly centered above the rim. Check both sides of the wheel.
19. Now fully inflate the tube. This will also help seat the tire; the air pressure forces the bead onto the rim shoulders.
20. Reseat the wheel on the bike by positioning it near the dropout. With one hand holding down the derailleur, lift the wheel into the dropout while simultaneously positioning the outmost cog under the upper part of the chain s circle.
21. Close the quick release by rewinding the handle and adjusting the quick release nut to the proper tension. (See Quick Release is Your Friend.)
22. Spin the wheel forward. Look to see if it sits straight and true, or if it wobbles? Does it appear to have the same placement as before the wheel was removed?
23. Close the brake release. Again spin the wheel forward, but slowly, and check that the brakes are evenly spaced on either side of the tire and not rubbing on the rim. If there is some rubbing, try snapping the brake lever while the wheel is spinning, then releasing it. This may adjust the brake. Otherwise, it may be necessary to remove and remount the wheel. Do not forget to close the brake release.

Source: T.K., Larry and Benny at Larry & Jeff s Bicycles Plus, 1690 Second Ave., New York, NY (2002)