My bike is being naughty

I have detected a small but very annoying clunk/crunch in the drivetrain.
I have removed the cranks and checked the BB...fine
Checked the pedals/tried with different pedals...fine
Removed the cassette...checked and fine so too the freehub
Wheels bearings lovely
Chainring?...tight
New chain and no stiff links
Removed jockey wheels and greased but they were fine anyway
and still I feel it!
Getting a bit peeved now :x

I know the feeling. One of mine has that too, and I've replaced every part that could cause it.

When does it do it?

i work in a bike shop and yesterday i had a bike exactly the same.. i took out everything and checked it all, gave it all a degrease and regrease, and got rid of any dirt in sight...
turns out it was simply the fact that the chain was replaced without also replacing the chainrings and cassette, my advice is check if the chain sits in the teeth comfortably.
also give it all a clean!
also check how tight your bolts are, too tight is not right, and too loose is no use!

I had this a while back also. Turns out the front mech limit screw were very slightly adjusted wrong and each time the slightly wider pins on the quick link went through they would catch on the front mech.
See if it happens in a consistent place and go from there.

Thanks for the replies.

Anthony":3k8ebrjo said:

When does it do it?

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Indiscriminately...high gear low gear, under load, light peddling etc

No front mech so it isn't that

New Sram chain (991) on very low miles M770 cassette...and I have run this a few miles with no issues

Front ring is renthal

Rear mech M810 SS

Rear hub Royce

My gut feeling is something with the chain cassette interface as you suggest Dj

Oh...and it does not seem to happen in the same place (on the chain )

Grr

weird - i think i have a similar problem.
it happens under light or heavy load (although the noise varies in loudness respectively)

it feels like the chain isn't sitting right on one of the cassette ring teeth and gives way a bit then becomes taught (regaining tension) as if its sat back in the teeth correctly.
this doesn't happen exclusively with any particular gear. it can happen when i take off or during a long flat easy straight.

this happens on my hardtail and my full sus.
Both of which have matching chain and cassettes of similar age and condition:
XT M737 rear cassette (mint but not NOS) with IG90 Chain (NOS)
XT M770 rear cassette (very little wear) with SRAM 9 speed chain (came with cassette as part of a complete transmission setup)

it happened before i added a quick link to my IG90 chain and still happens now. so i know its not down to that.

cant tell if it happens on the same part of the chain - highly unlikely though i imagine.

currently just ignoring it, but it has happened at junctions on rare occasions making it difficult for me to get away with speed and subsequently makes me a little nervous - very cautious when pulling out of junctions etc...

the only thing i haven't done is a close inspection of every single link, but even then, it could be something to do with the internals of one of the rollers in the chain.
its f**king annoying.

might it be worth posting close ups of each part of the drive train (cassette/jockeys & rear mech/chain rings/chain etc..)?

KMC chain?

suburbanreuben":m26f17qt said:

KMC chain?

Click to expand...

Sram 991 or whatever it's called

Have you tried with a spare derailleur?