About half the time I'd stop pedaling today on my ultegra Roubaix road bike I'd hear a mild popping noise that varied with speed...I assume inside the freehub (my guess, since nothing else on the bike is moving).
Additionally, about 25% of the time, there'd be a LOUD popping noise which coresponded with the chain getting sucked downwards as it rolled off the rear gear. The chain would sometimes hit the chainstay, then pop back up and do it again, and again until I started pedaling once again. During this time, the derailleur would be moving as well.
Again, all this is during coasting and no pedaling at all. Happened in at least 6 or 7 gear combinations.
Any help on the issue? Does the derailleur have some sort of tensioner? Wheel hub need greasing or new bearings? When I held the rear wheel in my hand (off the bike) and spun it, the cassette took only the lightest touch to keep it from spinning, so the bearings seemed fine when not under a weight load.