What's the procedure for tubular tire repair?
From: Jobst Brandt
Opening the Tire
To patch the tube, you must get into the tire and requires opening the
casing by peeling the base tape back and unstitching the seam. If this
is a seamless tire, chuck it. There are two types of seams, zipper stitch
(using one thread) and two thread stitch. The zipper stitch is identified
by having only one thread. It appears to make a pattern of slanted arrows
that points in the direction in which it can be 'unzipped'. Never open
more tire than is necessary to pull the tube out of the casing. Remember,
the tube is elastic and can be pulled out of a three cm long opening pretty
well. Even if there are two punctures not too far apart, the tube can be
pulled out of a near by opening. If you must insert a boot, you'll need
to open about 6 cm or about the length of the boot and then some.
Never cut the base tape because it cannot be butt joined. Always pull it
to one side or separate it where it is overlapped. (also: Don't cut the
tire seam, pull out the stitches.) When working on the stem, only unstitch
on one side of the stem, preferably the side where machine finished. Use
latex to glue down loose threads on a sidewall cut. Paint the exposed casing
zone that is to be covered by the base tape and the base tape with latex
emulsion, allow to partially dry and put the tape in place. Put the tire
on a rim and inflate hard.
Cut the thread at some convenient place at the upstream end of the opening
and, with a blunt awl like a nitting needle, pull out a few stitches in
the direction the stitch pattern points. Once you have exposed a length
of thread, you can pull the stitching out like a zipper. When you have
opened enough, take the loose end and run it through the last loop that
has not yet been pulled to lock the zipper. If you think the thread is
good enough, don't cut it off but use it to re-sew the seam.
Two Thread Stitch
One of the threads makes a zig zag as it locks the other thread where it
penetrates the tire casing. Cut both threads near the middle of the opening
and, with a blunt awl like a nitting needle, pull out a the locking thread
in both directions. The locking thread is the easier one to pull out so
remove as many stitches as you'll need to get into the tire. The other
thread pulls out like a zipper. Tie a square knot with the loose ends at
both ends of the opening and cut off the rest.
Patch butyl (black) tubes using patches from a bicycle patch kit.
To patch a latex tube make patches from an old latex tube that are fully
rounded and just large enough to cover the hole plus five mm. For instance,
a thorn hole takes a 10 mm diameter patch. Use Pastali rim glue wiped thinly
onto the patch with your finger. Place the patch on the tube immediately
and press flat. Latex will pass the volatile solvent allowing the glue
to cure rapidly with good adhesion to the tube.
Repairing tubular tires requires latex emulsion. You can get it from carpet
layers, who usually have it in bulk. You must have a container and beg
for a serving. If you are repairing them you probably ride tubulars, and
therefore, will have dead ones lying around. The best tubulars generally
furnish the best repair material.
Most cuts of more than a few cords require a structural boot. For boot
material, pull the tread off a silk sprint tire, unstitch it and cut off
the bead at the edge of the fold. Now you have a long ribbon of fine boot
material. Cut off a 50cm long piece and trim it to a width that just fits
inside the casing of the tire to be booted from inside edge of the bead
(the folded part) to the other edge.
The boot must be trimmed to a thin feathered edge so that the tube is not
exposed to a step at the boot's edge, otherwise this will cause pinholes
in a thin latex tube. Apply latex to the cleaner side of the boot and the
area inside the tire. Insert the boot and press it in place, preferably
in the natural curve of the tire. This makes the the boot the principal
structural support when the tire is again inflated. If the casing is flat
when the boot is glued, it will stretch the casing more than the boot upon
inflation. After the boot dries, and this goes rapidly, sew the tire up.
To replace the entire tube, open the tire on one side of the stem, the
side that seems to be easier to re-sew after the repair. Open about eight
to ten cm the usual way and pull out the old tube by the stem locally.
Cut the tube and attach a 1/16" thick nylon cord to the loose end of the
tube to be pulled through the casing as you pull the old tube out.
Cut the "new" latex tube about 5 cm away from the stem, tie the cord onto
the loose end and pull it gently into the casing. Dumping some talc into
the casing and putting talc onto the tube helps get the tube into place.
With the tube in place, pull enough of it out by stretching it to splice
the ends together.
Splicing the Tube
This procedure only works with latex tubes. Overlap the tube ends so that
the free end goes about one cm inside the end with the stem. With the tube
overlapped, use a toothpick to wipe Pastali rim cement into the interface.
The reason this MUST be done in place is that the solvent will curl the
rubber into an unmanageable mess if you try this in free space. Carefully
glue the entire circumference and press the joint together by pressing
the tube flat in opposing directions. Wait a minute and then gently inflate
to check the results. More glue can be inserted if necessary if you do
not wait too long.
Sewing the Tire
Sewing machines make holes through the bead that are straight across at
a regular stitch interval. For best results, you must use the original
stitch holes when re-sewing. Get a strong thread that you cannot tear by
hand and a (triangular) needle from a Velox tubular patch kit (yes I know
they are scarce). Make the first stitch about one stitch behind the last
remaining machine stitch and tie it off in a slip knot.
With the beads of the tire pressed against each other so that the old holes
are exactly aligned, sew in a loop stitch pulling each stitch tight, going
forward two holes then back one, forward two, back one, until the seam
is closed. This is a balanced stitch that uses one thread and can stretch
Now that you know everything there is to know about this, get some practice.
It works, I did it for years.
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