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Clunking over bumps, and loud/whirring rear derailleur

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Clunking over bumps, and loud/whirring rear derailleur

Old 06-29-16, 11:15 PM
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Clunking over bumps, and loud/whirring rear derailleur

Hey guys, recently got a used 2012 Scott CR1 Team.

Just noticed after a long ride that I'm hearing a *clunk* when I hit a bump in the road. I can reproduce the sound by holding the breaks and yanking back on the seat, and simultaneously forward on the handlebars. I then have to do the reverse to "reset" it before I can reproduce the clunk.

First thing I tried was tightening the headset, and it was already tightened so I cranked it up to a high 30 inch pounds, but tightening actually makes the clunking louder (but requires more force to do)! There is no visible play at all.

So I loosened the headset completely and tightened it so it was just snug enough to minimize visual play. Now rocking back and forth I can't hear it anymore but I can still feel the movement, but can't see any play anywhere. Any idea what this could be?

I also noticed my rear derailleur/cassette area whirs real loud while pedaling ... link to audio..

I suspect my rear derailleur hanger may be out of alignment, which would explain why I can only very cleanly index one part of my cassette. Here's what it looks like from the back, looks like it could be a few degrees off to cause that sound?

https://i.imgur.com/Ix5M5WP.jpg (sorry the image is too big to embed)

Thanks
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Old 06-30-16, 04:06 AM
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In my experience there is always some drivetrain noise. There has to be I think because of the cogs. A properly cleaned and lubed chain should be quiet, but I had a few brand new lower end chains that made a big noise even when I replaced both the chainring and the cassette. If the cassette and/or the chainring is worn that can make it louder too, or if you cross chain.

If you can't hear it while climbing slowly for example when there is no wind noise, or when you pedal everything feels smooth I wouldn't worry about it.

And yes that hanger looks bent, and I can hear that the RD is not adjusted properly. But you're right when the hanger is bent you can only adjust a few gears properly. Get a new one or take it to to your local shop, they can align it with a derailleur hanger alignment tool.
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Old 06-30-16, 06:06 AM
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The clunking is indeed most likely a headset problem. Either you aren't adjusting properly or it needs to be disassembled. I would have it looked at by someone more experienced. I don't think the hanger is bent enough to tell visually, but you have far too big a loop of housing at the rear derailleur.
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Old 06-30-16, 12:25 PM
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Thanks guys. Yeah, I do feel a slight feedback from the whirring in the crank. Lining it up in photoshop, there does seem to be a slight hanger misalignment, as the noise does persist after I cleaned/lubed the chain and cleaned the cassette. A longer housing loop at the rear derailleur wouldn't cause much of a problem as long as the shifters feel smooth, would it?

As for the headset, I'll try to disassemble it and regrease it and give it a look over. Thanks guys.

Last edited by Siu Blue Wind; 06-30-16 at 08:44 PM. Reason: clean up
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Old 06-30-16, 03:08 PM
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A longer loop can cause inconsistent shifting, due to greater friction going to the smaller cogs and more lever movement necessary in either direction before the derailleur moves. That would result in slow or partial shifts.
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