My wife’s bike is running a 9070 di2 rear mech. In the work stand the gears shift from one end of the cassette to the other without issue.

However when in the small chainring & 3rd gear on the cassette, underload (riding), the chain wants to move up to second, & in second wants to move up to first.

In the large chainring when in second selecting third nothing happens, then selecting fourth, it jumps down to fourth, again when riding under load.

To me it looks like it wants a couple of incremental adjustments down the cassette when in adjustment mode. However I find the mech at its limit of lower direction (right). The cassette locking ring is tight. The mech hanger looks straight.

The dealer manual on line states 12 increments of adjustment left & right from centre, 25 in all.

Any suggestions on what to do? Re-centre the mech & start again with set-up? Put a washer between the mech & hanger to space it right?

Id reset the limit screws. Id check the chain length and b screw adjustment on largest front and rear. Id take the central cog and use di2 adjustment to get it to run correctly. Other than that Id take the casette off and make sure its put back on fully and tightened down and gear hanger is straight. I find I need only a few clicks on the di2 leavers to get my setup to run correctly. TBH once setup it rarely if ever needs resetting. I just slap a new chain on and it runs prefect. I would not add washers etc. It shouldn’t need it. Have you changed from 11 to 12 speed? If so then software needs resetting? On the largest rings the rear mech should be pointing to 5 oclock if b screw and chain length is correct.

I would check your mech hanger alignment.

Out of 5 bikes, all 5 bikes needed tweaking.

It would seem a mech alignment tool really is useful (I was cynical before buying it).

My road bike (di2) went from not very nice gears to perfect.

(Well, perfect for a time, I think the hanger has been weakened/knocked – so plan on buying a new one)

I would say look at mech alignment, the servo is very very strong and in my experience can easily get out of alignment. When mine does that (6870) its nearly always alignment. You can get it happy for the central cogs but then it gets a bit weird on the edges.

If that is ok, and the limit screws are not getting in the way. then it might be that you’ve got a worn drivetrain. I also get that when I’ve worn out my fave rear gear, doesn’t like to change into it and then doesn’t like to change out of it. Time to replace chain and cassette.

Hope this helps.

Bent hanger. Common problem, always a bent hanger. Mine shifts beautifully, but is one gear out the whole way through the block with a slightly bent hanger, must fix it!

can max out the adjustment to get it ‘right’ but the shift is sloppy.

Thanks for the reply’s.

Was in Majorca at the time the issue occurred (but she’s told me its been like it for months but no issue as we don’t have big hills local at home). But its still an issue.

From the Specialized website archive the bike is a 2015 Tarmac S-Works Disc Dura Ace Di2 but we bought it used & the wheels had been changed to Mavic Ksyrium Pro Disc. The mech hanger appears perfectly flat on a flat surface but I ordered a couple from different sources for the model year. Both the new mech hangers are offset (cranked) but the original is straight. If I fit the new ones the chain gets trapped between the hanger & the bottom sprocket (although the offset in the hanger would address the issue of the mech being at the end of its lower adjustment range)

I’ll continue to search for the correct hanger but I’m not convinced its the issue. I’d take it to a shop but don’t want to be sold a new cassette, chain or even rear mech if its some simple issue.

If I fit the new ones the chain gets trapped between the hanger & the bottom sprocket

adjust the limit screws and adjust the shifting  – after that it sounds like you may have found a fix

No, there isn’t room for the chain between the hanger & the sprocket.

the hanger bends inwards ?

(although the offset in the hanger would address the issue of the mech being at the end of its lower adjustment range)

Sorry that’s wrong, it makes the issue worse.

Offset hangers are probably due to somthing Spesh call SCS. Google will provide on that.

Even with a new hanger I’d still check with a hanger tool to check it’s right as most are not

No, not bent inward, it has a parallel offset but the original has no offset. sorry cant post pictures.

I’ll take it to a shop & get a second opinion.

https://nextcycling.com/blogs/news/scs-faq-read-this-first-then-just-email-me-i-guess

Scroll down the page and the picture should help

I’ve just read that linked article on SCS – more proprietary bullshit.  What a bunch of **** !

orangeboy – well done & many thanks. So we have a SCS frame with standard wheels & hanger & when I try buy a new hanger I get sent an SCS item.