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Loud ka-CHUNK! when shifting gears

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Loud ka-CHUNK! when shifting gears

Old 09-19-18, 09:45 PM
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NoWhammies
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Loud ka-CHUNK! when shifting gears

What I hope will be an easy question/fix.

When shifting from one of the middle rings on the cassette to on of the smaller rings - in the middle of the cassette, but I'm not entire sure yet which ring - I will get a loud ka-CHUNK as the chain shifts down. The gears still change and there is no problem aside from the loud noise. Rather than it being a gentle quite shift, it's as though the chain jumps down to the ring with authority.

Does my description make any sense? My question though is how to get back to a nice quiet shift. The thing is, if I shift back up and then back down, it will do a nice quiet shift. So I can't get the loud/definitive shift to occur with any regularity.

Suggestions are welcome. Thank you.
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Old 09-20-18, 05:45 AM
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I would first check for cable/housing friction, as the cable may be catching briefly before releasing suddenly.
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Old 09-20-18, 07:30 AM
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I'd check the derailleur hanger alignment. That can cause that if it's just a skosh off.
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Old 09-20-18, 09:09 PM
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Excessive chain length & cable slop could be a cause.
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Old 09-20-18, 10:39 PM
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Make sure your cassette lockring is tight. Loose cassette cogs definitely make more noise (more of a "clack" than a "clunk") when shifting to the smaller cogs.
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Old 09-21-18, 12:13 AM
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This a modern hyperglide cassette, right, not a vintage freewheel?

Also, a homogeneous cassette, not mixing and matching parts?

It sounds to me like the chain is skating on top of the teeth momentarily, then dropping down.

Have you checked for chain wear? Any skipping from cassette wear?
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Old 09-21-18, 07:10 AM
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Sy Reene
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Originally Posted by NoWhammies View Post
What I hope will be an easy question/fix...
Suggestions are welcome. Thank you.
It was any easy question.. and you now have lots of suggestions
1. Cable/housing
2. RD alignment
3. incorrect chain length
4. cassette lockring
5. chain wear or cassette wear
Good luck.. you should offer a prize to the correct suggestion.
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Old 09-21-18, 10:17 AM
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Thanks everyone. My chain (according to the chain measuring tool) is at about 50% of life. I hope to get the chain to 75% of life before the end of my cycling season, but that may not happen. We'll see.
@Sy Reene thanks for summarizing the the suggestions for me. Much appreciated
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