Odd chain skipping problem - thoughts

[Binaural]

So, I've just installed a new pair of wheels on my daily driver. Whilst I had everything apart, I decided I might as well install a new chain and cluster and call it a yearly service, so I put on a new Dura-ace chain and an Ultegra cluster (28t). I've fitted a lot of new chains and clusters, and there was nothing unusual about how it all went together.

However, I have a strange problem. When I start to pedal under a small load to check everything, the tension arm on the rear derailleur jerks a bit and makes it sound like the chain's about to skip. When the bike is stationary, the chain seems to sit well into the jockey wheel.

I've fine-tuned the derailleur position, and I can change through the full range of gears. Initially I thought this was the upper roller was too close to the bottom of the biggest sprocket, but it looks like it has at least the recommended 2mm clearance (will post a photo shortly). I am a bit stumped; does anyone have any ideas?

Extra info: the rear derailleur is only about 10mo old, 11sp Ultegra short cage that should cover a 11-30 range. The chain I ordered is definitely 11-speed installed with the graphics facing outwards, using the old chain to get the length right. I gave the chain a good dose of Rock n Roll lube the night before, so it shouldn't be stiff.

 

[scblack]

Is your hanger bent?

 

[Binaural]

Here are a couple of shots showing the arrangement of the derailleur and the chain's position on the cluster. Any help much appreciated!

 

[Oddjob]

Did you use the pin or a quicklink?

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[Binaural]

@scblack I wouldn't rule it out, as the previous derailleur got bent when I accidentally went into big ring/big sprocket combo with an insufficiently long chain. Shifting was OK with the old chain and cluster though, so it seems unlikely.

 

[rangersac]

How worn are your chainrings?

 

[Binaural]

@Oddjob the pin. The chatter isn't once a chain rotation though, it's sort of constant like a fish pulling on a line.

 

[Oddjob]

Here are a couple of shots showing the arrangement of the derailleur and the chain's position on the cluster. Any help much appreciated!

I know you're in the inner west. You could always bring it to Smaug's cave of wonders, and I could eyeball it and use the derailleur hanger tool etc etc.

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[Binaural]

@rangersac Reasonably worn - bike does about 70km a week on my commuting run. I would not have thought they were worn out to that point though. I should try running the chain on the less-worn outer chainring and test your theory.

 

[Binaural]

I know you're in the inner west. You could always bring it to Smaug's cave of wonders, and I could eyeball it and use the derailleur hanger tool etc etc.

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Could be a good idea! Will get in touch if I can't work this out rationally in the next few days.

 

[stirk]

Chain suck is worn rings or sticky jockey wheel yeah?

 

[Cardy George]

Yeah, I'm looking at that jockey wheel.

Scored shaft maybe?

 

[The Duckmeister]

Has the lower jockey wheel ever been taken out for service, and if so, was it put back in the right way? Many more recent lower pulleys are asymmetrical, and have a particular direction to be fitted. They'll have an arrow to indicate the right way; it should be pointing in the same direction the chain makes it spin (clockwise when viewed from the normal perspective).

Did you also check the derailleur limits for the new wheel? Different brand hubs do have different cassette body offsets, so you usually do need to do a full retune when you change wheels.

The other thing that's been touched on is the rings. They're the last part of the system to wear out, when they are getting worn, they won't like a new chain. You'll often get a rumbly feeling through the crank under load, and if the teeth are really getting hooked can hang onto the chain when they're supposed to be disengaging, and that will pull the rear derailleur around a bit.

 

[Binaural]

Derailleur limits checked, gears shift fine. Jockey wheels have never been removed so that's one thing I am pretty sure is fine. If the jockey wheels are worn at all, it's not obvious.

Troubleshooting update: disappeared when using the less-worn outer chainring. Need a new chainring with this new chain it seems. Thanks for help all!

 

[SlowManiac]

The other thing that's been touched on is the rings. They're the last part of the system to wear out, when they are getting worn, they won't like a new chain. You'll often get a rumbly feeling through the crank under load, and if the teeth are really getting hooked can hang onto the chain when they're supposed to be disengaging, and that will pull the rear derailleur around a bit.

I've got this - new chain and cassette and getting that rumble/grind through the crank. New chain rings are on the way but can I keep riding or will I end up wearing out a new chain and cassette faster than usual?

 

[Binaural]

I've got this - new chain and cassette and getting that rumble/grind through the crank. New chain rings are on the way but can I keep riding or will I end up wearing out a new chain and cassette faster than usual?

A week or two should make no measurable difference to the life of a properly-lubricated chain. The only thing I'd recommend would be limited hard acceleration in the meantime as your chain is more likely to slip.

 

[ozzybmx]

Worn chainrings may be grabbing the new chain for longer, causing your rear derailleur to bounce.