I had the thrill of my life last June when I hit 86.4 kmh (53.7 mph) on a 1 km-long 14% descent in Lanaudière, Québec, on my Giant OCR Touring, despite the 700x32 tires. I'm rather heavy (220 lb) and I had a few things with me in a pannier. I particularly appreciated the disk brakes at the end of this crazy exercise... Since then, I hit 80 kmh several times, but I never broke my personal record...