Bicycle Mechanics - Rhythmic Pedaling Clunk no Cause

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?

Keep looking. Keep looking for clues. You'll eventually find it. If it only happens in the big or small chainrings, that's a clue. If it happens regardless of which chainring, that's a clue too. What's the position of the crank when you hear the "clunk"? I once had a soft "click" sound with every pedal stroke that drove me crazy. When I found it I felt really stupid. It was the crank striking the front derailleur cable with every stroke.

Speaking of feeling stupid, it never occurred to me that the peddle or crank arm might be hitting something (as I never imagine anything in that path) but that would explain the symptoms (as the clunking occures on any of the three chain rings). I'll check this out tomorrow and hope that's it.

Pedal bearing is shot?

chainring tooth?

Thanks to all for help about this. I'll look for each of these causes.

Speaking of feeling stupid, it never occurred to me that the peddle or crank arm might be hitting something (as I never imagine anything in that path) but that would explain the symptoms (as the clunking occures on any of the three chain rings). I'll check this out tomorrow and hope that's it.

I don't want to embarrass you so I'll ask this next question in code:

?dnatskcik a evah uoy oD

One of the standard steps for troubleshooting this type of problems is to replace clipless pedals with a cheap pair of platforms (shops end up with giant boxes of these and they can be had for about $5). This will eliminate the pedals and shoes in one step. Another quick and dirty test is to grasp the ends of your crank arms at the pedal ends and try to rock the whole crankset back and forth through the bottom bracket. You can find a lot of problems right there.

Since you have the same, or similar, problem in another bike it would lead me to be very suspicious of your shoes. I had a brand new shoe that had some delamination of some sort in the sole. It made a really crazy popping noise once every revolution. In the end, I got it to pop just by walking on it and really trying to flex the sole. Check that your cleats are tight. Use different shoes, if you can.

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?

1) check the bottle cage ---seriously...last time I had this mystery issue, it was a loose downtube botle cage, which I never noticed when stopped. It was rocking as I pedaled....yes I do throw the frame around a bit.

2) grease seatpost....not kidding. If it's a carbon seatpost, only grease if the manual says to.

3) veryfy BB torque setting is correct...if you don't torque-wrench your BBs, start.

4) Also verify the pedal body and the axle are not creating this through worn bearings or whatnot. I have had a pedal that turne dout to not be properly lubed at the factory do this to me.

Pretty much when you hit an issue like this, think about everything that recieves a rhytmhic stress related to your leg motions, and verify it's properly installed and lubed if necessary.

Not embarrassed at all. I don't have a kickstand on the bike, but I do use the large chaingring as a place to attach my lock while riding. Do you think that could have something to do with the difficulty in pedaling? :)

I just fixed a similar problem on an older bike of mine with square tapered crankarm mounts. The click/clunk went away when I removed the cranks, greased the taper, retorqued the cranks. That of course brings up the controversy over whether to grease the tapers ... I obviously side with those who grease.

As other posts have noted, the pedals are another possibility, so are the cleats, and of course interference from the front derailleur, bottle cages, etc.

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?


Both sides?

I just fixed a bike the other day for a lady describing the same symptom. Turned out to have nothing to do with her cranks. The wheel was out of true and the rim seam was bumping into the brake pad creating a dull thud.