Noisy pulley, HELP IS REALLY APPRECIATED !!!! Di2 DA7900 OWNERS HELP NEEDED !!!

[Tomazzz]

Hello everybody i really need some good advice how to solve my problem .

I bought a used bike , DA 7900 di2 system and this issue was already happening .

Here is a link representing the problem :

https://youtu.be/VcAq1QQV4LU

So basically I can see, hear and feel each chain roller hit a tooth on the tension pulley, before it sits in the valley between teeth.


A bit of info about a bike :

It is a team training bike , I bought it from a manager of the team , so he knows nothing , just that it was not in use for 6 month before i bought it .
DA 7900 mech , but crankset is 53 / 38 instead of standard 39 , 38 inner ring an is an aftermarket , but im sure that the problem is not about it , as I have the same sound on all gear combinations and on big 53 shimano ring also …
Everything works perfect and smooth , no issues at all , just dat pulleys (((
DA chain not stretched , i measured , washed it with degreaser and lube it with Muc-Off Hydrodynamic Chain Lube , checked every link , all good , no stuck or tight links.
Ultegra Cassette looks good , some wear , but nothing serious ...no bent teeth ...
Pulleys looks ok , almost no wear , I also took both of them off, washed with degreaser and lube it with Dura ace green lube , put everything back together , checked the direction – all as it should , but nothing changed in terms of sound (((
Hanger doesn’t look bent , indexing is perfect …
Wheels are true – also checked …

So I don’t know what to do , really (((

I found some posts representing the same behavior , but never a solution to that (((
So I really need your help , because I don’t really understand why it happening as I checked almost everything if not everything )))

Thanks to everybody in advance !!!

UDP : Can anyone with DA7900 check for such a noise , just wondering if it can be normal for that drivetrain.

Thanks.

[NATURAL ANKLING]

Hi,
Just wondering whether the hanger / idler frame is twisted so the idler is not running true with chain.
Or the chain is hitting the derailleur because the idler is the wrong way round?

Look from behind and see if the chain is straight between the idlers (you may have to pull the idler frame down with your hand against the spring to see this.

The chain is not routed properly through the frame and hitting a metal tag (this might not exist on your model.

[fastpedaller]

Looks to me as if the chain is too narrow.

[DaveP]

That pulley looks pretty worn to me - the trough between the teeth is much wider than what I can see on my bike. I suspect the situation is analogous to that of a worn sprocket. The effective pitch of the teeth on the pulley is greater than that of the chain and the noise results from the chain bottoming rather late on its passage round the pulley after initially riding on the shoulders of the trough.

[Tomazzz]

First off all , thanks for trying to help !

to NATURAL ANKLING :

The chain is perfectly straight between the pulleys , lower pulley (idler) is marked with an arrow for the direction and the direction is correct .
Nothing is twisted bent up there , cage plate made of carbon , i inspected for cracks , looks ok ...
Chain is routed correctly that's for sure as i checked it towards the manual . Chain length seems to be ok also .

to fastpedaller

Chain is CN-7901 so for 10 speed DA7900 group .

to DaveP

I thought worn pulley look like this

worn.jpg (10.76 KiB) Viewed 1641 times

Am i wrong ?

Thanks.

[DaveP]

Ok - As you were!
My suggestion wasn't based on the shape of the teeth, which don't look too bad FWIW, but on the shape of the trough between them, which is much wider than on my own bike. I also thought that I could see a flat section in the bottom of the trough, and at that point it is all starting to resemble the classic worn tooth pattern - but not quite as extreme as in your example.
I've just been looking at photos of replacement jockey wheels and realise that their new shape is actually very different to what I am used to seeing.
Sorry about that, Thought I'd cracked it for you...

[rfryer]

I've not had a chance to watch the video, but I had what sounds like a similar problem (on Campag Centaur) and it turned out to be due to the cage being twisted with respect to the rest of the derailleur.

I'm a trendy consumer. Just look at my XT1039 using hovercraft full of eels.

[Mick F]

My Moulton was doing exactly as your video shows.
Brand new bike, and it was doing it from the word go.

Eventually, I sorted it.
The issue was that the jockey cage when in the higher gears (outer and smaller sprockets) wasn't "pointing" at the outer chainwheel. This made the chain-run sort of catch the inner edges of the bottom pulley. The chain links had to "settle" onto the jockey teeth. Faster pedalling produced louder noises.

By taking an adjustable spanner and clamping it round the bottom of the jockey cage, I twisted it outwards just a tad.

Result: silence.

[nosmarbaj]

Even though you checked the cage itself is straight, are you sure the top pulley wheel is exactly in line with the sprocket in each gear? If it's a mm or so out of line, the noise could be from the chain on the sprockets rather than the lower pulley. The shifting might still work perfectly well.

NB I have no direct experience of Di2, so don't know if this is likely, nor how to fix it if it is the problem, but it's something I'd check on a manual system, in addition to others' suggestions above. (On a manual system it would just be a case of turning the cable tenson adjuster one or two clicks.)

[Brucey]

IIRC CN-7901 is a 'handed' chain, i.e. out of the four different ways you can fit the chain, only one is recommended, because the chain has a 'left side' and a 'right side' (as well as perhaps a 'top' and a 'bottom') which are different from one another.

More here

http://bike.shimano.com/media/techdocs/content/cycle/SI/Chain/SI_09R0A/SI-09R0A-001-Eng_v1_m56577569830688497.pdf

-in which it shows the correct orientation of the chain, and appears to indicate the chamfers that make the chain orientation-sensitive. Critically these appear to include handed chamfers on the inner side plates; if you don't have chamfers in the right places (on both the tension pulley and the chain) then the chain will be noisy as it engages with the tension pulley.



left side: right side

I had a quick look at your video and (going from memory) maybe the chain was fitted the wrong way round? If so maybe that could be helping to make the noise? If you have a quicklink installed then it isn't difficult to try it another way round?

BTW several still pictures (from all sides) is probably more useful if there is a possible assembly or alignment fault.

cheers

[MikeF]

If that's the case it looks as though left and right sides are correct, but a picture of the other side of the chain would confirm it.
Left and right handed chains - you learn something everyday from the forum!

[Mick F]

I still think it's jockey cage alignment.
Just as easy to check as the chain orientation. Just eyeball it in top gear.

[mercalia]

IIRC CN-7901 is a 'handed' chain, i.e. out of the four different ways you can fit the chain, only one is recommended, because the chain has a 'left side' and a 'right side' (as well as perhaps a 'top' and a 'bottom') which are different from one another.

More here

http://bike.shimano.com/media/techdocs/content/cycle/SI/Chain/SI_09R0A/SI-09R0A-001-Eng_v1_m56577569830688497.pdf

-in which it shows the correct orientation of the chain, and appears to indicate the chamfers that make the chain orientation-sensitive. Critically these appear to include handed chamfers on the inner side plates; if you don't have chamfers in the right places (on both the tension pulley and the chain) then the chain will be noisy as it engages with the tension pulley.



left side: right side

I had a quick look at your video and (going from memory) maybe the chain was fitted the wrong way round? If so maybe that could be helping to make the noise? If you have a quicklink installed then it isn't difficult to try it another way round?

BTW several still pictures (from all sides) is probably more useful if there is a possible assembly or alignment fault.

cheers

which clever dick thought that idea up? and why?

[mig]

mr shimano? so you buy his chain every time?

[Tomazzz]

So many people trying to help , THANKS !!!!!

to DaveP :

oh , i see now what you are talking about ) Actually you might be right !!!
I did not know that this tension pulley has , lets say a special edge shape

new pulley.jpg (10.63 KiB) Viewed 1475 times

new pulley 2.jpg (8.54 KiB) Viewed 1475 times

and comparing to it , my pulley really looks worn (((

I think it might result in links not getting to where they should go , just because this edge worn out ...(((


to Mick F

Everything looks extremely straight

And this is carbon fiber cage , so im not sure if you can twist it , i think you can only crack it , but not twist .


to nosmarbaj

indexing is perfect , chain is not touching any other gears on the sprocket , just the one it sits on )