When a race forces you to switch over to rain tires, use Intermediate Rain tires. Racing Rain tires don't quite serve your purpose, especially in those long 24-hour Endurance races. Racing Rain tires also have less grip, and thus force you to burn the tires up while trying to maintain your pace. Also, Rain tires last about as half the amount of distance, compared to regular tires. i.e. On Circuit de la Sarthe at Le Mans: 10 laps on Racing Soft tires = 5 laps on Intermediate Rain tires.