I have a strange issue with the clutch on my 11 speed GRX Di2 rear derailleur (everything is standard GRX besides the 11-40 SLX cassette). The shifting is terrible when the clutch is engaged, particularly in the small ring when shifting back up the cassette as it just won’t shift at all. The shifting is perfect otherwise. Micro-adjusting doesn’t help, the clutch has been serviced, I’ve tried another brand new rear derailleur, I’ve tried a new chain. I haven’t tried a new cassette as yet, but it doesn’t look worn. It’s not the end of the world, but it’s super frustrating at the same time!
Well, you are running a cassette outside of the range of that derailleur which will cause the b-gap to be too big for crisp shifting down towards the 11 tooth cog. You said that the clutch has been serviced, but didn’t mention if the tension of the clutch has been checked. Shimano has a range for clutch tension and too high will cause poor shifting, especially in the larger cogs of the cassette. The new derailleur doesn’t necessarily rule this out because I have seen derailleurs set too tight out of the box. I honestly think it’s a combination of the two contributing to the poor shifting.
I’ve got the same issue, my mechanic had never seen it before … but then a mate presented with exactly the same problem a few days later. It’s been a gradual decline in performance over the last couple of years. The hypothesis is that the gears within the rear derailleur are getting worn, and can no longer shift freely under tension of the clutch. If true, then it can be expected that this will become more common as more rear derailleurs reach an age / wear limit. In my case, it’s not the hanger nor the clutch tension settings.
You mean the guide and tension pulley wheels? I assume you do given the clutch doesn’t have any gearing.
If this is what you mean, throw in some new pulley wheels. Even if visually the teeth on the pulleys are OK, if there is too much lateral play, the guide pulley will have trouble pushing the chain over to the next cog.
Correct, if you run a drivetrain outside of the spec on the compatibility chart then you may have issues, it’s unsupported for a reason regardless whether a friend got it to work or not.
I mean the gears within the motor inside the rear derailleur, those that drive the gear changes (not the pulley wheels external to the DI2 motor). It’s a hypothesis, time will tell whether this becomes more prevalent or not. In my case, it’s not related to the hanger, pulley wheels, clutch tension, etc. as far as I can determine.
I had a similar issue, but it was cable actuated 11 speed GRX. With the clutch on shifted terrible and sometimes you could not downshift to large cogs as the whole system will get extreme friction in it. I couldn’t push the brake-shift lever without fear of breaking something. Clutch off it was fine. I rebuilt the clutch, turned down the clutch spring, etc. All for naught, had to get a new derailleur.