8b.28 Mounting Tubular Tires
Description
This article is from the Bicycles FAQ, by Mike Iglesias with numerous contributions by others.
8b.28 Mounting Tubular Tires
From: Jobst Brandt <jobst.brandt@stanfordalumni.org>
Date: Fri, 26 Jan 2001 01:01:01 PST
Two kinds of glue are used to secure tubulars to rims, road and track,
the latter having become uncommon. Over the years many glues have
been available by: d'Alessandro, Clement, Continental, Michelin,
Vittoria, Wolber, Pastali, Tubasti, and others. With the decline of
tubular use, these brands have become so scarce that riders in the USA
turned to other sources, one of which was 3M Fastack (R) that compares
favorably with the others and cures faster than most.
Road tubulars preferably should have a rubberized base tape, one
coated with latex, to improve adhesion to pressure sensitive glues.
These glues behave similar to typical sticky tapes, sticking better to
slick surfaces than cloth, so that rubberized base tapes stick better
to partially dried rim cement than to bare cloth. Do not modify
tubular base tape with cleaning solvents because they affect rim
cement adversely. Track tubulars, to be glued with hardening
adhesive, should have bare cloth base tapes because shellac type track
glues adhere poorly to rubberized tape. Hardening glue is used on
track tires to avoid rolling losses typical of pressure sensitive rim
cements.
Because road tires are intended to be changed on the road, their glue
must be manually separable and reusable; it must be sticky. However,
being gooey, it allows the tire to squirm on the rim, which causes
rolling losses independent of inflation pressure. That road tires
move on the rim is apparent from the aluminum oxide (dark grey) that
invades rim cement during use and cloth textured wear marks from base
tape in the rim.
Mounting the Tire
Stretch the new tubular tire on an old rim, inflate hard and let stand
while applying cement to the rim on which the tire is to be mounted.
Rim cement dries fairly rapidly, some faster than others. If this is
a low viscosity rim glue, it may require more than one coat. Apply
additional coats when the previous one has become firm enough to not
draw strings when pressing the finger into it.
When a good coating (0.5mm) of rim glue has set enough to be firm to
the touch, deflate and remove the tire from the stretching rim and
mount it on the glued. With the wheel standing upright on the floor,
start by inserting the valve stem into the rim and stretch the tire,
pulling down with the hands to both sides away from the stem, working
around the rim until reaching the bottom with only a short section of
tire not yet in place. Lift the wheel and thumb the remaining section
onto the rim. Inflate the tire enough for it to take shape, centering
it on the rim before inflating hard.
Were the glue still soft and mobile, it would get on the sidewalls
while mounting the tire. Glue should be firm enough to not make a
mess. Because pressure sensitive glues are also thermally sensitive,
heat from braking, while descending montians, often melts rim glue
enough to make it flow from under the tire in contrast to hard (track)
glue. While track glue (Tipo Pista) is more cumbersome to use, it has
its benefits for heat but primarily for timed events where fractions
of a second make a difference.
Mounting track tires is done the same way as with road glue only that
it takes several coats of shellac, the last of which must not be
allowed to dry, so the bare cloth rim strip will be wet by the glue as
the tire is inflated. Mounting the tire cleanly is more difficult and
removing the tire sometimes requires tire irons.
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