A few days ago I read a interview with the guy from Bristol speedway that's in charge of the track. He stated that the banking will be at 18 degrees. He said that the last time it had dirt on, it was 24 or 27 degrees. He said that the track was redone since it was dirt the last time and the angle of the outside wall has changed where it meets the track surface. 18 degrees will keep it at the correct angle to keep the cars inside the track if impacted by one of the cars. He stated that is the reason, not to slow the cars down, it's to prevent cars from getting launched into the catch fence. I can't remember where I read it. Possible on Dirt on Dirt Maybe.