Not totally tubeless: The Nuetech Tubliss
system does use a small tube.
Putting tubes inside tires is so old
fashioned that it’s hard to believe
that motocross technology hasn’t
gotten out of the 1970s. What is
holding up tubeless motocross tires?
It is true that tubes generate heat,
add weight and are the weak link of
motocross tires, which makes many
people dream of tubeless motocross
tires. Tubeless motocross technol-
ogy has actually been tried many
times. Famous tire technician Frank
Stacy has been working on tubeless
motocross tires since the 1980s. “We
began development of the tubeless
tire technology in an attempt to build
an overall lighter wheel to reduce
unsprung weight and to benefit the
suspension as well as reduce rotating
mass for better power,” said Frank
about his time working for Dunlop.
Unfortunately, Dunlop found that if
you use the same tire pressures that
work on conventional tubed tires on a
tubeless tire, the rim can be damaged
from under-inflation. Even worse,
once you bend a tubeless rim, the air
in the tire escapes. Since the tube
adds substantial sidewall stiffness
that isn’t present in a tubeless tire,
the rims used with a tubeless tire
would have to be beefed up to take
the increased abuse.
Dunlop also learned that the tire
bead wasn’t the only area where a
tubeless tire could leak air. It could
also escape out of the spoke holes.
Dunlop tried everything from a
special, wide rubber bands to silicone
sealant. Most tubeless tire companies
discovered that a silicone seal was
the most effective but also the
messiest to apply (and it took time to
set up). The rubber-band-style seal for
the spokes was easiest to use (and
sealed well), but if you did get a flat
tire, the rubber band would fling out
and wind itself around the rear brake.
Without the inner tube adding
stability inside the tire, Dunlop
discovered that the sidewall of the
tire needed to be a lot stiffer to
reduce flex and prevent rim damage.
This and the need for an airtight
bead resulted in a heavier tire. So,
unfortunately, the system that started
out as a way to reduce weight actually
ended up adding almost 2 pounds.
Another factor holding back the
development of tubeless motocross
tires was the need to sell a rim with
the tire. This made the product too
expensive for the average rider.
Special tubeless rims would allow
for the more generous tire bead
and special rim-seat shape required
to not only keep the air inside the
tire, but to keep the tire on the rim.
Why would a new rim seat shape
be necessary? Because even if the
bead is airtight, when the tire flexes
over bumps, air can become trapped
between the bead and rim. If air
sandwiches between a long enough
section of bead, it can blow the tire
off the rim or burp out air pressure.
To solve some of these problems,
Alpina of Italy made a special tube-
less tire rim. On the Alpina rim, the
spokes threaded into special nipple
couplings, which in turn threaded
into the rim. Alpina eliminated the
sloppy fit between the spoke nipple
and the rim, and in doing so
eliminated a source of air leaks.
Street bike tires do not take the
abuse of a motocross tire. Plus, they
don’t have to be as light because
they aren’t free-spinning. Street bike
and automobile tubeless tires have a
special butyl liner inside the tire
casing to help hold air and
strengthen the carcass. Unfortunately,
this would add weight to a motorcycle tire—and motocross tires can’t
afford this weight gain.
Tubeless tires haven’t been a
complete failure in motocross,
however, as they found success in
the mid- to late-’80s on works bikes.
They have been raced on the GP
circuit and in the AMA Nationals and
Supercrosses. Riders who have spent
time on tubeless race tires include
Georges Jobe, Jeff Ward and Ricky
Johnson. Some factory riders loved
their tubeless systems, but Dunlop
back-burnered the program due to
the cost and lack of interest by the
majority of the factory teams. Even
with high-end racing success and
factory testing, tubeless tires have
never come to the local level.
The only consumer-ready tubeless
motocross tire system is the simple
and ingenious Tubliss system. It isn’t
a tubeless tire, but rather a creative
way to turn any tire into a tubeless
tire by installing a small-diameter
bicycle tire inside the rim to seal the
gap between the two tire beads. It
doesn’t require special rims, sealant
or one-off tires. Plus, it saves weight,
doesn’t cost as much as a single tire,
and can be moved from tire to tire
as the knobs wear off. As the sport
sits today, Tubliss is the best way to
go tubeless. To read more about the
Tubliss system, turn to page 134.