Images copyright Dave Lynn & Steve Dilts
Text copyright Michael J. Fuller
In addition to the Nissans, Juan Fangio in the All American Racing Toyota Eagle MkIII also fell afoul of similar tire issues. From the cockpit Fangio had witnessed both Nissans’ accidents and the team decided to tell him to slow down fearing a similar failure, “They said to me, ‘Juan, there is a tire problem, and we are on the same choice as the Nissans,” says Fangio. “The big problem was that my mind didn’t allow me to slow down. You can do this when you feel something wrong in the car, but this was not the case, because the tires were good until they were not any more.” Fangio’s tire delaminated at the most inopportune place on the track, the dip between turns 9 and 10 and ultimately not too far from where both Nissans went off, “The only problem was to slow down the car from over 200 miles per hour, going through the big dip on the twisty straight, miss the bridge and make the turn."
concerns about downforce apparently predated the Road Atlanta incident; while
Goodyear were developing the 1992 tire they inquired with the teams regarding
the downforce levels they were running.
It turned out that Goodyear had underestimated how much downforce the
cars were generating by some 20%.
Naturally the tires were designed to the information the teams provided
and not the Goodyear estimate, but the point was that by 1992 the aerodynamic
pace of development had quickened to the point where even the tire companies
were caught by surprise.
struggled to come up with a conclusive reason for Nissan's tire
being unable to recreate the mode of failure in testing, and could only
that the tire batch in question was at the limits of its life
cycle. And while that most certainly was the case,
it isn’t much of a stretch to say that the downforce loads the cars
carrying exacerbated the situation. But another finger might
point at the static weight of the cars coupled with high downforce
Of all the IMSA GTP competitors,
the Nissan was carrying the most overall weight. This was primarily a factor of the IMSA
regulations at the time and ultimately Nissan was in mid strides to correct this by
changing their philosophy to that of their competitors. On IMSA’s sliding scale of
weight vs. engine capacity, the Nissan weighed in at 2100 lbs as they were
running the maximum turbo capacity of 3.0 liters. But
all of Nissan’s competitors,
Contrary to the Nissans,
At the extreme end of the weight scale, the Jaguar XJR-14 was the lightest GTP in the field. From 1990 onwards (upon the announcement of the pending changes in Europe for 1991), Group C derived 3.5 liter formula prototypes were allowed to race in IMSA at 1750 lbs. In combination with the Group C spec underfloor, the all up regulation weight was a controversial 1650 lbs. Ultimately the IMSA-ized XJR-14 gained weight as components were beefed up and TWR never did reach the 1650 minimum with the car. But even in its debut race, the Miami GP, the Jaguar was tilting the scales at a lithe1680 lbs.
Obviously Nissan was cognizant of the advantages of all of this and was working hard to put the NPT-90 on a diet for 1992. A reduction in turbo engine capacity to 2.5 liters would move the Nissan 100 lbs down the weight scale. And fitting a Group C spec underfloor to the car would make their new
target weight 1900 lbs; a full 200 lbs under where they started the season at. This would be
achieved by analyzing every aspect of the car’s design and finding weight
wherever it could be pared. This would
mean ounces off some items, pounds off others. But destroying two cars so early in the season certainly
issues; in order to prove these new, lighter items, the team needed two
be circulating the test track, not to mention the race track. But
at Road Atlanta the Nissan was still at 2100 lbs; the weight reduction
program was in-process and bits were only just trickling onto the car.
While the root cause of the tire failures was never determined, the
Nissan’s more than 2100 lbs of
static weight in combination with around 7000 lbs of dynamic “weight”
(Kas Kastner indicates the failures occurred while the cars were still
accelerating and at an estimated 185 mph) probably put them in the best
position to exacerbate
any underlying tire issues. And even Nissan’s
Trevor Harris hinted to as much in On-Track magazine at the time (June 12, Full Chat section) referring to the
we'd be remiss in not mentioning an additional suggestion to the source
of the failures. We've been told it could have had something to
do with running lower than the recommended tire pressures in order to
gain a traction advantage. This suggestion came to us courtesy of
another competitor, one that was also running massive levels of
downforce but did not have any tire issues at the event. Though
naturally this is just further speculation.
Regardless of the cause, the result was
detrimental and shook Team Nissan to the core. Trevor Harris
simply stated, “We never really recovered
from that weekend.” Indeed, the team was
unable to consistently field two cars following Road Atlanta and their
1992 title bid fell flat (though their second place in the
Manufacturer's Championship flattered to deceive; they only won one
race that year).
Chip Robinson's accident (14:18):
Geoff Brabham's accident (36:52):
Images come from screen shots taken off the ESPN broadcast
ęCopyright 2009, Michael J. Fuller