NATURAL RUBBER
So much for Mickey Thompson's recommendation
of racing with tubes. Now, what kind of tubes
are we talking about? Francis said Mickey Thompson
recommends running a natural rubber tube, and
for a couple of reasons.
First, it conforms to the wrinkles of the slick,
because modern slicks are all wrinkle-walls.
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"That's
the secret of a slick working nowadays -- the
sidewall wrinkles, and the wrinkles help spring
the drag car off the starting line," he explained.
A racer can buy a very inexpensive butyl rubber
tube at any K-Mart or tractor shop, and there
are some pseudo-racing tubes out there today
that have the clamp-down valve stem that do
not use natural rubber, Francis says. One way
to tell a good racing tube from a bad: its price.
"Anytime a tube is cheap, it's not natural rubber.
It's just against the laws of business. You
just can't find an inexpensive natural rubber
tube. It just doesn't exist," he said.
The second reason natural rubber is preferable
is that it helps dissipate heat better than
butyl rubber. Factor those two considerations
in and you'll find that a good rubber racing
tube is cheap, plus it's cheap insurance for
the slick itself.
A SCREW-IN CLAMP
What else about a good racing tube? Mickey
Thompson also recommends getting a tube with
a screw-in clamp that will clamp the valve stem
to the wheel. The reason here is that it helps
keep the valve stem in place should there be
any movement. If there is movement, say, if
the wheel spins inside the tire, it will tear
that stem off. And because of the low pressure
involved in racing with a drag slick, you could
suck the valve stem inside the wheel, "and that's
obviously not a good thing either," Francis
said. A set of wheel screws tapped into the
wheel itself and piercing the slick's bead should
also be a necessity when racing with slicks,
too.
TUBES NOT FOR E.T.
But there is at least one application where
you do not want a tube, and that's with a car
that is ET-oriented, not built for consistency
like for bracket racing. We're referring here
to the heads-up racer, maybe the 10.5 guy who
is looking for every bit of elapsed time. Francis
says for him not to run a tube in this application.
"The tube is additional weight that is unsprung,
and it will affect the performance of the car
-- it's just more weight -- so if that's the
case in general, when a guy has evolved to heads-up
racing from bracket racing, he'll be watching
his air pressure more closely between rounds,"
he said.
If the tubeless tire leaks down in the garage
during the week, the edge of the rim can cause
damage to the cords of the tire if it lays on
it for any length of time. If a guy has a tire
that's going to leak because there's no tube,
then he should be putting something underneath
the axle, to prevent the wheel from bottoming
out on the garage floor.
MOUNTING
Okay, so how do we now mount our slicks? Mickey
Thompson says to use a dry lubricant like baby
powder. Do not use anything liquid, especially
something like antifreeze, silicones or petroleum-based
lubricants along the bead or inside of the slick,
or on the tube itself. "You have to use a dry
lubricant, and you do need to have some sort
of lubricant there so that the tube does not
stick to the tire and it is free to move inside
the tire," Francis said. Wet lubricant is out
-- it will promote sticking and bonding between
the slick and the tube.
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