Di2 chain slap

[thebadgerboy1982]

Hi all,

Ive had this issue from new but i couldn't track down what was causing the issue!

Ive got a short cage ultegra 6870. Chain length is fine and the chain isn't worn or stretched. On smooth tarmac not a sound. But as soon as its a little rough, the chain slaps off the chainring at the bottom. its as though the chain is jumping off and on the chainring. doesn't matter if its in the large or small chainring.

it seems as though there isn't enough tension provided by the rear derailleur. I've adjusted the b screw and it hasn't changed it.

Any ideas? its on an sworks tarmac with a 9000 chainset and ultegra chain.

Thanks
Ross

[SL1]

Check chainring bolts are tight. Check the crank is fully seated in the bb.

Are the chainrings excessively worn ? Could it be chain suck ?

[TheKaiser]

But as soon as its a little rough, the chain slaps off the chainring at the bottom. its as though the chain is jumping off and on the chainring. doesn't matter if its in the large or small chainring.

it seems as though there isn't enough tension provided by the rear derailleur. I've adjusted the b screw and it hasn't changed it.

Are you certain that the noise is coming from the chain/chainring interface? It is possible that it is hitting your chainstay?
It can be a little tough to tell whats going on down there while riding, but you should be able to see marks on your chainstay from the chain hitting it to tell if that is the cause.

Also, does the problem occur when pedaling or just when coasting?

[maxxevv]

Check you RD B-screw. It may need some minor adjustment to take out the slack in the chain.

[pdlpsher1]

I have the 9070 and recently I traced an issue to the pulley cage. The rotation of the pulley cage (what keeps the tension on the chain) against the derailleur body was stiff. This prevented the pulley cage keep a consistent and even tension on the chain, thus causing the chain to skip on the cassette. Upon disassembly of the pulley cage I found the bolt holding the pulley cage to the derailleur body to be overtightened at the factory. This had caused the carbon fiber pulley cage plate to rub against the aluminum derailleur housing, causing severe binding and friction. Check your pulley cage. By design the cage should move smoothly and free of any friction. The one other possibility is a broken pulley cage spring that keeps tension on the pulley cage.


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[thebadgerboy1982]

Well, turns out i made a rubbish job of fitting the chain. Used the Big chainring biggest cassette plus two links as normal. Used the park tool calculator and the chain slap is 99% gone!

[nycebo]

I have the same problem as you 'had'. When you adjusted your chain, out of curiosity, I assume it got smaller by a link or two?

Well, turns out i made a rubbish job of fitting the chain. Used the Big chainring biggest cassette plus two links as normal. Used the park tool calculator and the chain slap is 99% gone!