In an effort to not have as much 2 car drafting and bring back pack drafting to Daytona, NASCAR has made some changes to the Aerodynynamics of the cars…loosening them up and decreasing the size of the radiatoris so that cars cannot push eachother. A down side to this is that when you do push someone you have to be very accurate. Push to the center or slightly to the right of the car in front of you…but if you push the left corner of the car in front of you he spins out automatically. The problem is that you used to be able to do that without too much problem in the past…but now this happens (see below).
Source: http://www.youtube.com/watch?v=LE8pSnKmb8U
Source: http://www.youtube.com/watch?v=GaYMsZwRsmQ