86km/hr down Col de la Madeleine toward Albertville, France. That was this August (2004) on a tandem with a BOB trailer loaded for camping for a month. We were near the top above treeline on one of the few straight stretches. The tandem has wide tires and no disc brakes.
Yesterday I took said tandem down Magnolia Rd. in Boulder, Colorado and hit 80 km/hr with no gear.