Chassis Help! Need a track day set-up.

SG4247

I am new to the road course deal, and have my Z in the shop now prepping for track days in April.

This car is a 2010 touring model, with rear adjustable camber arms and toe bolts. Stock suspension components otherwise.

I just installed new RE-11 285/35/19 F on 19x10, and 325/30/19 R on 19x10.5 wheels, and did a four wheel alignment.

Car works pretty good, except that when I go through a long sweeping 45 degree turns at high speed (VDC off), the car begins to wiggle. At first I thought it was porpoising, but after several attempts on the same corner turning both left and right, the car has a significant wiggle coming from the rear.

This happens under full power, part throttle and coast at a certain speed. For example, it is stable through the corner at 80 mph holding part throttle, but when I increase the power say mid-way thru the turn, to increase speed to 85 mph, to blast out of the turn exit, the wiggle comes on and continues even though the tires do not feel like they are sliding or spinning, the car is still under my control, even if just barely.

If I suddenly brake during the corner when the car begins to wiggle, the outside front tire will lock up, and chatter due to the ABS.

Very strange behavior to me, is this car pushing? Is the different tire widths causing this?

Not sure how fix this problem, but I dont like it.

Any help would be greatly appreciated.