I’ve ridden mine in plenty of horrible weather. Probably around 40-50% of the rides I did so far as it’s a very wet summer in Europe this year. No issues apart from the one time when I sealed the plug afterwards.
Also, after fine tuning the indexing further, shifting performance and chain tension with 52/36 up front and 11-34 in the back is absolutely fine. I’ve been doing a lot of climbing this week and used the whole range of the cassette and had no issues.
The only thing that keeps happening to me is that on bumpy descents when braking before a corner, I do sometimes accidentally hit the front shifting button and drop the chain to the small ring. Pretty annoying but not a huge issue. It just has to do with the ergonomics of the shift buttons and the brake lever and where my hands are. The textured button protrudes ever so slightly too much from the brake lever IMO. So I have to pay attention to not grab the lever the wrong way, otherwise I’ll push the button by accident.
I've been hesitant to wash my bike, but since I don't ride in the rain often it only requires a wipe down after every ride. Maybe when winter comes, I'll test out the ER9 in wet conditions. It seems at this point, as long as the rear derailleur battery cable is protected, the ER9 should be okay.
When I sized up the chain length for 52-36/11-34t, I found it more prone to chain slap. It was too loose for my taste. I removed 2 chain links and went down to an 11-32t cassette instead. It feels much more concise at that length and I can still climb at that gearing, but I do rely on my lowest gear more often. Compared to my gravel bike running an Ultegra RX800 RD, by far the spring tension even with the clutch is off, is much more firm. I'm wondering if it's just a cost-cutting measure by LTwoo or if Shimano has some patent on beefy rear derailleur springs?
I also occasionally hit the left shift button when on bumpy descents. When I first installed the groupset it was an issue, but now that I'm aware of it, it's been less of an issue.
