Mark , I had to use both the front air dam and the rear deck spoiler at the speed I was running . To keep air from getting under the car , the air dam was modified for 1 inch ground clearance at the bottom . The car was very stable at speed and was still accelerating at the mile marker . Dan the official speed was 171.2 mph. my GPS showed 172.4 mph. The car did not falter at the start , that was me trying to keep the tires from spinning . For this event I was running on Pirelli Trofeo R tires . It is a very good track tire and Y speed rated but only 225 mm wide. With 417 lb. feet of torque at the tire , the gas pedal gets to the floor at the end of first gear.