Chain clunck coming off big cog under load

[teeonethousand]

I have a 'clunk' coming from the chain when in lowest gear under load ie going up hill. Everything changes fine up and down . I traced it to the way the chain link comes off the cog...every few teeth the chain brushes the tooth with enough tension to make it clunk as it releases it . I can see the chain twitch . This is in big rear and small front and although the chain line is obviously not straight I would still expect it to be smoother. Plenty of clearance at front derailleur.

I am taking it to lbs in the morning as I only bought it in Nov24. Revolt Grx 2x12.

Opinions appreciated but I'll update anyway after visit tmrw if anyone is curious .

 

[Dogtrousers]

Possibly the "B" screw in the derailleur. This screw governs how close the cage is to the cassette. If it undoes itself (as mine is in the habit of doing) the cage starts fouling on the big sprocket.

Also known as the "end adjust bolt" I think.

What rear mech do you have?

 

[teeonethousand]

Possibly the "B" screw in the derailleur. This screw governs how close the cage is to the cassette. If it undoes itself (as mine is in the habit of doing) the cage starts fouling on the big sprocket.

Also known as the "end adjust bolt" I think.

What rear mech do you have?

Grx 820..it's not that...all adjusted as per manual ..also tried it with bigger gap and no difference

 

[teeonethousand]

Grx 820..it's not that...all adjusted as per manual ..also tried it with bigger gap and no difference

Plus...I could understand that if the misalignment was it going onto the cog but this is it coming off at the top as it heads over to the front ring.

 

[C R]

No stiff links in the chain?

 

[fossyant]

Stiff link would be my first check

 

[Yellow Saddle]

I have a 'clunk' coming from the chain when in lowest gear under load ie going up hill. Everything changes fine up and down . I traced it to the way the chain link comes off the cog...every few teeth the chain brushes the tooth with enough tension to make it clunk as it releases it . I can see the chain twitch . This is in big rear and small front and although the chain line is obviously not straight I would still expect it to be smoother. Plenty of clearance at front derailleur.

I am taking it to lbs in the morning as I only bought it in Nov24. Revolt Grx 2x12.

Opinions appreciated but I'll update anyway after visit tmrw if anyone is curious .

Some clarity for me please:
1) Cog - as in tooth or as in rear sprocket?
2) Chain link - the joining link or any link in the chain?

As an early guess, you have a mismatch between chain pitch and sprocket pitch - worn chain and possibly rear sprocket too.

 

[Paulus]

Some clarity for me please:
1) Cog - as in tooth or as in rear sprocket?
2) Chain link - the joining link or any link in the chain?

As an early guess, you have a mismatch between chain pitch and sprocket pitch - worn chain and possibly rear sprocket too.

I was going to say a worn chain, and or cassette.

 

[teeonethousand]

Worn chain it is...or was...new one on now.

It had lasted only about 800 miles and I had thought, mistakenly, the chain would typically last a couple of thousand miles. kMC replaced with Shimano.

Thx all 👍

 

[Paulus]

Worn chain it is...or was...new one on now.

It had lasted only about 800 miles and I had thought, mistakenly, the chain would typically last a couple of thousand miles. kMC replaced with Shimano.

Thx all 👍

KMC chains normally have a good reputation, i run them on my bikes with good longevity out of them.

 

[Webbo2]

Worn chain it is...or was...new one on now.

It had lasted only about 800 miles and I had thought, mistakenly, the chain would typically last a couple of thousand miles. kMC replaced with Shimano.

Thx all 👍

Careful where you buy your chains from. Theres lots of forgeries on EBa.

 

[silva]

A test may have been flipping the chain, to see if the clunk disappeared, but too late now.

 

[teeonethousand]

Careful where you buy your chains from. Theres lots of forgeries on EBa.

I bought it from the LBS who is a Giant Dealer that I bought my bike from in November. The bike came new with the KMC Chain.

Thx again all

 

[gbb]

Worn chain it is...or was...new one on now.

It had lasted only about 800 miles and I had thought, mistakenly, the chain would typically last a couple of thousand miles. kMC replaced with Shimano.

Thx all 👍

Is 800 miles an anomaly or somewhere about normal for you ?
I'd generally get 1800 per chain and even that seems low compared to some ..but then I used to ride out the saddle a lot, I think that puts even more pressure on a chain.

 

[teeonethousand]

Is 800 miles an anomaly or somewhere about normal for you ?
I'd generally get 1800 per chain and even that seems low compared to some ..but then I used to ride out the saddle a lot, I think that puts even more pressure on a chain.

I expected more But don't have enough history to tell. The LBS mechanic said it was about normal.