Road bike, standard setup. Every 3-4 pedal strokes, in every gear, there is a clunk/click that reverberates through the crank arms so that I feel it in both feet. I tightend the crank arm bolts, but no difference. I put it in the trainer and listened closely, and it sounded like it was coming from the cassette.
I'm currently giving the whole drive train a good cleaning, any ideas if that doesn't work?