If you have been following the Greatrace updates you can't help but
notice that Steve and Janet are scrambling to dial in times with a new
set of tyres.
In order to drive a distance and arrive within a couple seconds of your
predetermined time you need to know the exact diameter of your tyres
during the race. All the calculations count on this information being
accurate.
And of course each tyre can have a slightly different diameter from the
factory and air expands when the tyre heats up changing the diameter of
a tyre. Tyres used for the Greatrace are cut to a known diameter when
new and are filled with nitrogen to minimize variation in heat expansion.
Before the race, The BP Land Rover underwent a number of timed speed and
distance tests out in the Southern California desert to dial in the
calculations needed to compensate for tyre expansion and to find the
tyre pressure that yields the least amount to expansion during race
conditions. The difference between a top experienced team in first
place and a top experienced team half way down the field can be just a
matter of how closely the tyre diameter calculations are to the actual
diameter.
The British Pacific race car was flat towed from the the West coast to
the East. At the race starting point they discovered that the tyre
compound was too soft for a long distance race and the tyres had worn
enough to completely throw off all their carefully tested numbers.
With the help of Coker Tyres the Land Rover was soon shod with a new set
of tyres with a harder rubber compound, shaved to a known diameter and
filled with nitrogen.
So with no time for retesting the team started the race not knowing how
much the tyres will expand under race conditions nor the optimum tyre
pressure to minimize expansion during the race.
I thought you might be interested in knowing why they are paying so much
attention do dialing in the tyres during the race.
I'm sure Steve can fill you in better than I. If you have any questions
their email address is: Pe1624@aol.com
TeriAnn
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