[s-cars] future of awd and TT handling
colin cohen
ccohen5 at compuserve.com
Thu May 17 13:23:02 EDT 2007
So we tried a number of different tire pressure combinations on the TT while
racing it in the SCCA T3 National event two weeks ago. I got stymied on
qualification and in one of the races by failure of first one and then
another of the spark plug power packs but here is what we did learn.
Softening the front shocks (rebound and compression) helped front end grip
measurably as did higher rear tire pressures. On one session I measured a
hot pressure of 42 having started at 38 and a fairly even cross tire temp
starting at 150 on the inside and declining to 135 on the outside. This is
consitant with the rear camber and a lot higher ( ambient was 75) then I
have seen in recent events indicating that I am sliding the rear a little.
The fronts were also mid 40s although we started cold at 33, with temps at
170 plus - very much in the zone for Hoosiers.
Note I am running an asymmetrical wheel tire combo too with 17" 235s on the
rear and 16" 240s up front. My times were 2 or 3 seconds better than my
last run but Don Istook was able to effect the same improvement with just
the softer shocks. The only corner that upset the ECU (limp mode until the
wheel was straight and I got off the gas) was a slow 300 degree hairpin.
Fortunately the track out exit is so wide that I was able to adapt my
technique to take the corner in 2 phases, getting on the gas only in the
second phase where the steering wheel had very little turn. But it was the
long way around and this offset the torque advantage I would have otherwise
enjoyed over the Honda S2000 and RX8s in the class.
So thanks for the help everybody.
Colin
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