Ideally, tires are round and stay
that way. But at high speeds they
warp in a number of ways. Speed
makes them grow in height, lessening
the contact patch, unless the track is
banked, in which case the g-forces
push down and enlarge the contact
patch. Where the damage is done to
the tire is when the tire comes off the
contact patch.
In simple terms, the contact patch
is flat and oval-shaped - the tire is
round. In the rolling transition from
flat to round the tire deflects slightly,
like a lazy speed bump, before
assuming its shape again. (You can
see a similar deflection on a chain as
it comes off the countershaft sprockeL) The transition effect out of
NASCAR Four is heightened because
the tire is going from a big contact
patch, which the banking and gforces impose, to the smaller patch,
created by the expanding tire on a
flat surface as the speed increases.
Throw in the mix dual-compound
tires - tires that have a hard side and
a softer side joined in the middle.
"That's where the damage is
done," Allen explained about the
turn-four transition. "That sort of
force can lead to tire changes. The
best tires recover quickly. That's
what we have to design our way out
of. The balance between the two
(Opposite page) Dunlop tire guru Jim
Allen talks tires with American
Honda's Miguel DuHamel, the first
AMA Superbike rider to try dualcompound tires at Daytona.
(Right) Mr. Daytona Scott Russell
takes off on his new mount, the HMC
Ducati.
(Below) Doug Chandler discusses
setup with his crew chief, Gary
Medley.
compounds is the trick. There are
one or two that can do the job [and
Dunlop spends a lot of time trying to
figure out which ones]. What we're
trying to do is get these through a 67mile stint with no problems, and what
they [the riders] are looking for is
grip. The two don't go hand in hand
at Daytona."
They never have.
Allen is, himself, a former racer
who rode TZ750s at Daytona all
through the '70s. Back then,
Goodyear was the only tire company
to race at Daytona and you took what
they gave you.
"Goodyear told us this is what
you're riding on and it was an
absolute rock. They didn't have any
competition," Allen said.
In the mid- '70s the development of
the TZ750s outpaced tire technology
so quickly that the 200 had to be run
in two 100-mile legs in 1977 because
the tires wouldn't last. Instead they
cue. e
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JANUARY 17,
2001
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