Joined: Jan 2009
Posts: 44,139
Likes: 6,365
From: New York, NY, and High Falls, NY, USA
Bikes: 1962 Rudge Sports, 1971 Raleigh Super Course, 1971 Raleigh Pro Track, 1974 Raleigh International, 1975 Viscount Fixie, 1982 McLean, 1996 Lemond (Ti), 2002 Burley Zydeco tandem
batman_3000, heavier things go faster downhill only when the air resistance is the same. Actually, it's the air drag/weight ratio that makes the difference. The weight of a carbon bike with rider is about the same weight as a steel bike plus rider. The difference isn't likely to be significant since the air resistance is the same.
A feather lands more slowly than a pebble only because of its air resistance, not its weight. If there were no air, they would fall at exactly the same rate.