I just did Sebring 2 weeks ago, my car has engine mods, but otherwise bone stock.
I ran it with BFG R1 Slicks. Now, keep in mind I just sold my 2000 GT with the entire Maximum Motorsports catalog in it. This was very different, a little "unsettled" but over all very stable.
The car ran great, it did everything it was supposed to. I did not drive it at 10/10ths of course. It did feel a little "Floaty" at speed, and I did lose the rear a few times, but at that time I was trying to push it.
As you know, its a MUCH better platform right out of the box from the old platform.
I did NOT have any understeer issues, but again I was running 275 35 18 slicks.
The only other mods I did in preparation for the weekend was Front brake cooling, Motul fluid, SS lines and Hawk DTC70 brake pads up front. Stock rears. The car also has 4.10's, 3.73's going in this week. 4.10 is a bit to much.
At 16 seconds in I did a 4-3 shift, instead of 5th. First time that ever happened, just not used the trans. I've only owned this car for a month or two. I got a little loose again at 1:30 in, decided to back off at that point.
If you have any other questions, let me know.
Future mods are:
CC Plates
Koni Yellow's
H&R Race spring
Front sway bar
Adj. PH bar
Keeping this car much more street friendly than my old car.
http://www.youtube.com/watch?v=0Prs0ZduCrk&list=UUPA-YSQtK-jqvDlDn3lCYTw
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