Di2 thinks in wrong cog
 

My bike won't shift into the two smallest cogs in the rear when it is in the large chain ring up front.

When I connect it to e-tube, it "thinks" it is in the smallest cog. It shifts fine into the other cogs going up and back down aside from those bottom two cogs.

I have tried the crash recovery mode, and it shifts up, hits the largest cog and stops. When it hits that cog, it thinks it is 2 from the top.

The bike shop checked the derailleur hanger and it is straight and didn't need adjustment.

I adjusted the offset to +and -16 and the best I can get it is to one away from the bottom. But I don't think that is a reasonable solution.

I would like to just reset cog it thinks its in, but I can't seem to figure this out. The local shop has never seen this and tried everything they could think of, but they can't seem to get any farther than I have.

Edit: There was a comment about a spacer on the cassette. However, The bike is using the original cassette that has never been off the wheel, and the wheel came off the bike, and until the other day it shifted flawlessly.

Any help would be appreciated.

Depending on your rear cassette size, Di2 when in the big front will not shift to the two smallest tooth cogs. Your bike shop guy should know that. Embarrass him me thoroughly. Unless you do have the configuration that allows shifting to all the rear cogs.

I think you have to have less than 28 teeth on your biggest rear cog for it to shift to them. You can fool it by just telling it you have the smaller cassette size in e-tube, but then you might have more slack in your chain when going to those cogs and shifting performance will be affected or maybe you'll drop a chain more often.

Knowing exactly what model Di2 you have might help too. I'm just giving you my R8070 Di2 experience off the top of my head.


EDIT.... I goofed. See my pitiful excuse in later reply!

umm, it's not the bike shop guy who should be embarrassed here.


When in the big chainring, Di2 should shift to every single cog in the cassette.

Go to bettershifting.com. This guy know everything about Di2. Yes, on the big ring, it should shift to every cog.

Or just tag TerryDi2C in this thread. If anyone at bf has a solution, it'll be him!

Durn, I hate it! I was stupid when I answered earlier. My feeble excuse is that I must have been delirious from the heat and sun after helping my wife rip out the early spring flowers out of the front flower beds and put in the late spring and summer flowers. We'd just finished and this was one of the first threads I read when getting in out of the sun.

Little while later when out for my 32 mile ride, on the first false flat where I like to get up as much speed as I can for a ¼ mile this thread suddenly was foremost in my mind. I panicked and thought about heading home immediately to correct my mistake, but then said fudge it. Only like little Ralphie, it wasn't fudge.

So have at it. I accept my shame willingly. Just glad most of you others must have still been out riding and I got to address my stupidness before too many saw it in all it's glory... or lack thereof!. <grin>

I knew it was just a silly mistake! :)

My silly guess, we all get one, right!

These is a spacer between the cassette and hub that just shouldn’t be there.

Barry

Is your bike shop an authorized Shimano dealer or service center? If so, they should be able to get on the phone with Shimano and figure this out.

For DIY, I'd go back through the DM for it's installation and make certain every i is dotted and t crossed.

https://si.shimano.com/api/publish/s...010-01-ENG.pdf

https://si.shimano.com/#/en/search/S...8150&type=ROAD


Chain line might be an issue here if you are installing a group set made for road on a mountain bike or vice versa.

Ok, let’s go really basic

if you remove the wheel, does the RD now move as expected, all 11 positions (10 moves) ?

Barry

I also sent this via email, but thought I might as well reply to the thread as well ;-).

Sometimes a Di2 rear derailleur is just off by 2-3 gears. It doesn't happen often, but it does happen. There is no real way to fix this. You cannot use E-Tube Project 3.4.5 / 4.0.4 / 5 or the SM-PCE1 / SM-PCE02 to fix this.
I don't know whether or not this is possible with E-Tube Project OEM, but since no one other than factories has access to that it doesn't really matter :).

Shimano's method to fix derailleurs that are off by 2+ is to replace them. Usually they'll also replace them if it's out of warranty.

A derailleur hanger or frame that are slightly out of spec (too thick or too thin) is also a possibility... but you would then end up with a derailleur offset one gear at most. Two seems a bit excessive.

Since a bike shop has already looked at the issue it's pretty safe to say that the hanger is straight and that the derailleur is installed correctly. They should've called Shimano though, and I think that is the next step to take ;-)

Wow. That is useful info. I’m gonna file that away in case I ever have this issue.

There is no spacer in there. The cassette has never been off the wheel and it worked flawlessly before the other day.

This isn't a constructive comment but - every time I see this thread I think of a goofy blues song "Thinking with the Wrong Head", a state of "mind" that has happened to many men! Read those last couple of posts and "hmmm, just maybe the derailleur has gone down that path." Doe this bike have a foxy front derailleur?

Details like that will always be useful to know. Though it probably wouldn't have helped explicitly, it might have changed some opinions offered.

But on the more immediate quest for a solution.... how is that shop doing getting hold of Shimano?

Hi All,

I stumbled on this thread after having a similar issue recently.

I am on 11 speed Ultegra Di2. On my ride this weekend I realised that I couldn't access the two BIGGEST cogs on my cassette.

My head unit indicated that I was in the biggest cog, but the derailleur (RD-8050) was in the third biggest.

The e-tube app also thought the RD was on the biggest cog.

The system was also trying to change down beyond the smallest cog.

I took it to the LBS; and they had Shimano remote connect to the bike to investigate.

Shimano are none the wiser for why the fault occurred; but the fix was to replace the rear derailleur.

Very strange fault. The broken derailleur had down about 17,000km since new. Not exceptional, but nothing to complain about either. I'm just happy to have it be up and running again.

LBS also found you, Terry on Instagram I believe - thanks very much for your help. It was this post, and this reply which made me realise I couldn't fix this at home and needed to get to the LBS so that they could work with Shimano.

Cheers

Mike

There is someone on Instagram, by the way, that repairs Di2 derailleurs - @Di2_gp .

I'm still learning how to repair these, but Pawel @Di2_gp) does to quite often. He is based in the UK :)