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Expeditions
to stony desert, rocky or thorny areas, to name a few, may require more
than one spare wheel and tyre. It may become necessary to replace a
tyre and/or repair a puncture yourself.
The manufacturer's jack is rarely suited to expedition use and a small hydraulic jack together with a ratchet type Hi-Lift
jack (Farm Jack) is an ideal combination.
Tubeless
Radial tyres:
Punctures should only be repaired in the tread area which is normally
in contact with the ground. Sidewall damage is not repairable. A tubeless
tyre repair kit can be easily used to repair a hole upto 1/4in dia.
A typical kit consists of some cord, adhesive and a bradawl type needle.
Procedure: dip the needle in the adhesive and push it carefully through
the puncture. Remove it and thread the cord through the needle, leaving
about an inch on the short side. Dip the needle and cord in the adhesive
again and push it through the puncture so that the short end of the
cord is completly inside the tyre. Remove the needle and trim the excess
cord to about 1/8in. Pump up the tyre.
If the tyre leaks air around the rim then remove the valve core with
the tool from your tyre
maintenance kit and inject some tyre
sealant according to the instructions on the can, re-insert
the valve core and inflate the tyre. A double
action foot pump saves effort here if you don't have an electric
tyre compressor. Purchasing a complete tyre repair kit is advisable.
If
the puncture is too large to repair it may be possible to still use
the tyre by fitting an inner tube. Some tyre manufacturers permit tubes
to be used in some of their radial tyres, others do not. An innertube
must be of the correct size for the tyre. The tyre will have to be released
from the rim.
A 21st century approach is to use a commercial latex sealant solution which is injected into the tyre through the valve (sometimes the valve core needs to be removed first). The tyre is then pumped up and driven. Heat generated in the tyre causes the sealant to set as it is squeezed out of the puncture hole. Several modern 4x4's have a similar solution already installed in the tyre pending a puncture.
Removing
a tyre
The first problem is to 'break the bead' i.e the bonding of the
tyre to the rim. You probably don't have a bead breaker and certainly
not the hydraulic equipment the tyre fitting workshops use. The best
alternative is to use your hydraulic jack. First remove the valve core,
put the wheel under a stong part of the vehicle chassis and jack down
the tyre from the rim, using the chassis to push down against. Take
care not to damage the tyre and keep the jack vertical. The tyre will
pop down into the wheel centre. You can stuff a few rags between the
bead and rim to prevent them re-seating. Repeat the process for the
other bead.
To lift the tyre bead over the wheel rim long
tyre levers are needed.
Stand on one part of the tyre to press it into the centre of the rim
and use a lever to prise the bead over the rim furthest from where you
are standing. Hold down the lever with one foot whilst using the other
lever to prise the next section of bead over the rim. Be careful not
to damage the bead edge of the tyre. Continue until all the bead is
released.
If you are removing the tyre then a similar procedure is used to get
the other bead over the same side of the rim. If however, you are installing
or repairing an inner tube
there is no need to remove the tyre completely.
Replacing a
tyre
Apply a little soapy water to the bead and use the tyre levers
to prise the bead onto the rim. For the second bead, stand on the
tyre opposite the part of the bead you are prising over. If the tyre
is a cross-ply then pump up the innertube to push the bead back fully
onto the rim. If the tyre is a radial then you cannot produce enough
pressure with a foot pump to lift the tyre bead onto the top of the
rim. Without a commercial 'bead expander' you can improvise by wrapping
a rope tourniquet-style around the middle of the tyre tread and tightening
with a tyre lever whilst pumping. The sidewalls will bulge out and
the beads jumps up onto the rim.
Repairing an innertube
If it becomes necessary to repair a punctured tube that has a
small hole in it then a self-adhesive repair
patch is the best option. These simply need to be pressed firmly
onto the cleaned surface and left for a few minutes to bind. The inside
of the tyre should be carefully inspected to remove any material that
may rub against the tube and damage it.
Alternatively, tyre sealant can be used as for a tubeless tyre.
Installing an innertube
The bead should
be broken on both sides and prised over the rim on one side. Pump
just a little air into the tube to separate its sides. Remove the
tubeless valve stem. Insert the valve stem of the tube into the hole
in the rim and push the rest of the tube into the tyre. Take care
not to allow the tube to become twisted. Add more air to the tube
to keep the valve in position. Check the tube for twists and wrinkles.
Apply a little soapy water to the bead and use the tyre levers to
prise the bead over the rim. Be careful not to trap the tube with
the levers or to damage the bead. Stand on the tyre opposite the part
of the bead you are prising over. Check the tube is not trapped anywhere
and pump to the desired pressure and check with a tyre
pressure gauge.
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