I work for Bell Motorsports (the overall winner of DP) The reason the race was red flagged was because all of the tire manufactures ran out of rain tires for the competitors. Goodyear, Dunlop, and Hoosier were OUT of rain tires. Teams were having to purchase used rains from other teams that dropped out of the race. Besides the tire situation, track conditions were horrible and during the red flag, it was raining so hard on pit road, crews could hardly see. Grand-am made a wise call for safety reasons as well as supporting their tire companies. With 55 cars requiring at least 18 sets of rain tires each... there was a severe deficit of rains.