Look at how rise in the rear of a drag car gets less and less the faster the car gets.
As acceleration decreases in a slower car, controled seperation keeps the tire loaded enough for good traction. Once you get enough weight and g force planting those tires to get the front off the ground, you don't need any. It takes virtually no seperation and about eight inches of forward travel in my dart to get there. My carhas the power to keep the tires planted very early. A high 10 sec car not as much. Every car and situation will vary.