Double clutching can be used on the track to save your transmission from damage/abuse, but it WILL cost you lap time.
At Hawaii Raceway Park there is a hair pin at the end of the straight. Your coming down from a 100 plus and high gear to 1st gear. I don't downshift through the gears (into 3rd then into 2nd). I brake HARD and when making my 4th to 1st gear shift I would on occasion double clutch to 'save the synchromesh'. After all, lap after lap shifting so many times your really putting a LOT of wear on your trans. If I wasn't in hot pursuit, I'd rather give up a little time in favor of racing again someday AND getting my trans home in one piece!
I know many of the older 'sports cars' I had over the years had VERY weak 1st gear synchros, shifting them hard into 1st could ruin a synchro pretty darn quick! I always double clutched my Austin Healey, 1st gear synchro was all ready gone when I bought the car. Triumph's were also notorious for loosing the 1st gear synchro (this from personal experience). I learned to drive in a VW with non synchro 1st, so it comes kind of natural to me anyway.
Double clutch, save the synchros!
