Hard to say exactly in any car really. First of all it's all about power to weight. The roadster weighs about 90 lbs more than the coupe. (btw the crossfire has about 90 lbs of extra body and chassis reinforcement over the slk I've driven the slk and the srt6 is tighter). Then figure in how much the driver weighs (I weigh about 155 lbs) and how much gas is in it ( gas weighs about 8 lbs a gallon) The lighter the car, the more all this matters. Also, air density (altitude) and temp affects a blown motor more. The srt6 has 19's in the rear, the slk has 18's.