I know the 11-23 cassette is not made anymore, but is there a reason why it would cause shifting problems with Di-2? I have it on my bike, and it works pretty well but i can’t dial in the shifting perfectly. When I switch to an 11-28 cassette the shifting is always perfect.
Did you adjust the b-limit when switching to the smaller cassette?
You should probably specify your set-up. Which RD are you using? FWIW, back when I had a 6770 RD, it worked perfectly with a 11/23t 10-speed cassette.
That said, the 9150 (and presumably 8050) SS RD has an optimal lowest cog tooth count of 25t to 30t (so that would work well with your 28t but not a 23t).
Previous generation 9070 and 6870 SS RD have an optimal lowest cog tooth count of 23t to 28t, and those 11-23t speed cassettes could still be found here and there.
FYI, tech documents from Shimano, which specify the cog teeth range.
https://bike.shimano.com/…-di2/RD-6870-SS.html
https://bike.shimano.com/…-di2/RD-9070-SS.html
Good point echappist.
The rear derailleur is a
Shimano Ultegra Di2 8050, 11 spd RD-R8050-SS
so an 11-23 cassette is definitely not in the specs.
I did pull out the Shimano manual and go through the entire installation and setup routine to make sure that is was dialed in as perfectly as possible.
It really shifts OK with the 11-23 except when I try to shift from the 18 to the 17 tooth gear, it won’t shift. I have to double shift from 18 to 16, then down shift to the 17. Everything else shifts perfectly. It is not a huge problem, really just a mystery.
As soon as I drop in the 11-28, everything is perfect.
Looking at the gearing, I should probably just go with the supported 12-25T.
11-12-13-14-15-16-17-18-19-21-23T
11-12-13-14-15-16-17-19-21-23-25T
11-12-13-14-15-17-19-21-23-25-28T
12-13-14-15-16-17-18-19-21-23-25T
How old is the cassette and chain? Sometimes a new chain does wonders.
It really shifts OK with the 11-23 except when I try to shift from the 18 to the 17 tooth gear, it won’t shift. I have to double shift from 18 to 16, then down shift to the 17. Everything else shifts perfectly. It is not a huge problem, really just a mystery.I am running the same RD with a DA 11-23 cassette, and mine is doing this exactly. I thought it was OSPW - not obnoxiously oversized, just a little bit. Mine works OK most of the time, but it does occasionally fail to shift unless I double-shift & then corrective shift.
How old is the cassette and chain? Sometimes a new chain does wonders.
Good idea. The chain is very new, clean and lubricated. The cassette is a little older but still only a few thousand miles on it. No visible wear.
One more piece of information, last night I bought a 12-25 cassette. I put it on the bike, opened the etube app to update it with the new cassette, but I forgot to hit “Apply” so it still thought it had the 11-28 cassette on the bike. I got the same sifting problem that I experienced when I had the 11-23 cassette. I went back into the etube app and set the cassette properly and the shifting was perfect. No other changes. So, it might be the case that the Di2 actually changes shifting based on what cassette is installed!