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Di2 rear derailleur adjustment question

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Di2 rear derailleur adjustment question

Old 05-25-21, 10:47 PM
  #1  
nemeseri
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Di2 rear derailleur adjustment question

I have a bike with Shimano 9150 and I ran into a strange rear derailleur adjustment problem.
I set up the indexing properly, but in this case the rear der wants to over-shift the chain into the spokes and won't shift to the smallest sprocket.
If I move the indexing to the outmost position (in the direction of the smallest sprocket), shifting works fine and all gears assigned to the right sprocket, but half of the gears are noisy as hell... and I'm sure that it's not normal to move the index adjustment to any end of the range completely.

I adjusted the B screw and noise is not coming from the rubbing of the pulleys.

Obviously I think that the hanger is bent... but after eyeballing it... seems totally fine and definitely not out of alignment with one full gear.

Any suggestion I should try? Thanks!!
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Old 05-26-21, 12:30 PM
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Cog

Assuming you're using an 11 speed Cassette, it sounds like you had the RD in the wrong cassette cog when you begin to perform the alignment.
It sounds like you were one cog too big when you began.

BTW - are you aware that Di2 will stop you cross chaining? Can you reach Big Ring - Smallest Cog ?
Because Small Ring - Smallest Cog goes against the wishes of the Shimano Gods!


Barry

Last edited by Barry2; 05-26-21 at 12:35 PM.
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Old 05-29-21, 09:43 AM
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If the indexing works fine on one end of the cassette but not the other, it's a sure sign the hanger is bent. If the indexing works fine with the chain on one ring up front but not the other, it's a sure sign the hanger is bent. If the indexing worked fine but then unexpectedly stopped working, it's a safe bet the hanger is bent.
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Old 05-29-21, 10:19 PM
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Originally Posted by oldbobcat View Post
If the indexing works fine on one end of the cassette but not the other, it's a sure sign the hanger is bent. If the indexing works fine with the chain on one ring up front but not the other, it's a sure sign the hanger is bent. If the indexing worked fine but then unexpectedly stopped working, it's a safe bet the hanger is bent.
So I replaced the hanger (I do not have a tool to check the alignment)... and the issue stayed the same. Then out of curiosity I swapped out the rear wheel and boom: issue is gone. The original wheel seems to be true and I checked the torque on the cassette... Should I replace the cassette to see if that helps? Thanks.
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Old 05-30-21, 09:17 AM
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How are you adjusting the indexing? With a screwdriver, eTube Project or other?
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Old 05-30-21, 02:34 PM
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Originally Posted by Iride01 View Post
How are you adjusting the indexing? With a screwdriver, eTube Project or other?
I press the junction button for a few seconds and adjust it with the shifter buttons in adjustment mode.

I didnt even know that there is a way to adjust it with a screwdriver. How?
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Old 05-30-21, 02:50 PM
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Originally Posted by nemeseri View Post
I press the junction button for a few seconds and adjust it with the shifter buttons in adjustment mode.

I didnt even know that there is a way to adjust it with a screwdriver. How?
There isn't. All you can adjust with a screwdriver are the limit and b-screws. And if the limits are too close in, the derailleur has a way of letting you know.
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Old 05-30-21, 03:01 PM
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Originally Posted by nemeseri View Post
I press the junction button for a few seconds and adjust it with the shifter buttons in adjustment mode.

I didn’t even know that there is a way to adjust it with a screwdriver. How?
Originally Posted by oldbobcat View Post
There isn't. All you can adjust with a screwdriver are the limit and b-screws. And if the limits are too close in, the derailleur has a way of letting you know.
oldbobcat gave the answer. I was just being sneaky and making sure you weren't futching with the limit screws.

You might find a computer with eTube project on it a little easier to see what you are doing.


If this is a new setup, then I'd go through the Shimano Di2 manual for the setup and adjustment.

If this just started happening to a bike that otherwise worked before, then I'd suspect the hangar got bent. Or perhaps your cassette is loose.
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Old 05-30-21, 03:14 PM
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Originally Posted by nemeseri View Post
So I replaced the hanger (I do not have a tool to check the alignment)... and the issue stayed the same. Then out of curiosity I swapped out the rear wheel and boom: issue is gone. The original wheel seems to be true and I checked the torque on the cassette... Should I replace the cassette to see if that helps? Thanks.
With Di2, one trouble spot you can eliminate right away is sticky or worn out cables. The rear derailleur is going to move the same distance laterally each time you shift, and that distance will equal the center-to-center spacing of the cassette, unless it is the wrong cassette. I presume you're using a Shimano cassette with the correct spacers. It's also a safe bet that if you did something that would damage a cassette to affect its shifting, you would have damaged something far more obvious. Perhaps I'm wrong.


I've lost count of new hangers I've had to align. I imagine they come pretty straight from Wheels Mfg., but perhaps the dropout is out of alignment, or perhaps the hanger isn't seating in the dropout exactly as the manufacturer envisioned. Whatever, I'm in the habit of aligning new hangers because I've found new hangers to be out of alignment. And generally, I only replace a hanger if it's been mangled beyond straightening, or if it's about to break off. And generally, I've found that reluctance to check hanger alignment stems from not having the tool and not wanting to take the bike to someone who does. Or buy the tool. Really. This is easier and cheaper than replacing cassettes and hangers that likely don't need replacement.
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Old 05-30-21, 03:22 PM
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Originally Posted by Iride01 View Post
If this just started happening to a bike that otherwise worked before, then I'd suspect the hangar got bent. Or perhaps your cassette is loose.
On 11-speed, if the cassette is loose, that means it's about to fall off. Yikes.
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Old 06-01-21, 01:20 PM
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FWIW, I made the mistake of buying a set of Carver wheels that were built up on Novatec D771/D772 hubs and ran into the exact same issue. Drove myself crazy trying to get my Shimano Ultegra Di2 RD to properly cover all 11 cogs on the cassette. Tried various spacers, checked hanger alignment six ways for Sunday and still no joy. Talked to Novatech support but all they suggested were the same things I'd already tried. I finally sent the wheels back for a refund. Ended up building a set of wheels using DT Swiss 350 hubs and had no trouble whatsoever getting the RD to index on all 11 cogs of the same cassette I'd tried on the Carver wheels. Had I the patience to take careful measurements on the Novatech hub, I probably could have discovered the source of the problem,
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Old 06-01-21, 01:44 PM
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OP,
I have 12mm thru axles, Mavic Ksyrium wheels, and use an Ultegra 8000 11speed cassette with a RD-R8050 all on a Cervelo R3.
So standard stuff.

From the rear of the bike I can measure from the inside of the dropout to the face of the cassette lockring 7.8mm
If your's is significantly different, then the cassette is in the incorrect position.

Barry
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