In races that force 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 force you to burn the tires up trying to keep the pace up. Another tip that is safe to say is that Rain tires last about as half the amount of distance, compared to regular tires. On Circuit de la Sarthe at Le Mans: 10 laps on Racing Soft tires = 5 laps on Intermediate Rain tires.