C-Sig Training Series�
CHANGING A REAR TIRE�
- 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.
- Open
the brake release (do not unscrew it).
- 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.
- 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.)
- Lay
the bike down, gear side facing up.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.�
- Now
fully inflate the tube.� This will
also help seat the tire; the air pressure forces the bead onto the rim
shoulders.
- 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.
- Close
the quick release by rewinding the handle and adjusting the quick release
nut to the proper tension.� (See Quick
Release is Your Friend.)
- 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?
- 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) �������� ���