I have a question: What is the pit crew member doing when he puts that "tire iron" into the rear window of the car and rotates it? I watched the Xfinity race yesterday and saw them doing that and the commentator referenced the car being too tight or too loose. What is the rotating tire iron affecting on the car?
Those are called wedge adjustments - adjustments made when the driver complains the car is tight/loose:
http://auto.howstuffworks.com/auto-racing/nascar/jobs/nascar-wedge-adjustment4.htm