Similar to an earlier post, but not the same, I have this problem with a mountain bike: Every revolution of the pedals produces an audible clunk sound that I can also feel in the pedals, though it doesn't interfere with the pedal stroke. This sound does not occur when coasting. I checked: (i) the pedals against the crank-arm; (ii) the crank against the bottom-bracket; and (ii) the bottom-bracket in the bottom-bracket shell. All tight and snug and moving freely. I'm stumped. I have the same noise in a different mountain bike, but that bottom-bracket is loose in its shell and tightenting it will do the trick, I know from experience with that bike. But what's the problem if nothing is loose?