Momentum, Force, cycling and skiing

OK, so I know in a vacuum that a feather will fall to the ground just as fast as an anvil (F=ma). What my simple mind can't figure out is why - when I'm cycling - a portly guy like me will gradually pass the leaner/cooler dudes going down hill? It's the same deal with Down Hill ski racers, the bigger skiers carry more momentum into the flats (can you say Bode Miller) and, ergo, finish quicker. So I have the momentum thing down [mv]: I have more momentum when I'm cycling than the lean and mean folks. But how do I reconcile the constant acceleration idea. According to Newtonian mechanics - ignoring friction - I should go downhill at the same pace as the little guys??? Archived source: https://web.archive.org/web/20101205105518/http://www.spacetimeandtheuniverse.com/general-physics/4430-momentum-force-cycling-skiing.html