I thought I’d try this as I’ve seen it claimed as successful elsewhere.

I’ve used an M985 mech with OneUp cage, M8000 shifter snd M8000 11-42 with PC-X1 chain.

First note is that even with the OneUp cage the B screw barely copes with the 42t.

Second thought is that shifting down the cassette works fairly well but shifting up it skips a bit in the middle. Cable tension doesn’t resolve the issue.

So, having got this out of my system, I’ll put an 11sp mech in there. I suppose it would be usable but it would annoy me not being able to depend on a shift actually happening. I was wondering if anyone else had tried this?

The 11spd mech is much better generally that the 10 speed one.

I’d hope the correct item was better at the specific task!

I was just interested to see for myself how well the cross worked, and having seen it wondered if anyone else here had tried it…

Got that combo running fine, but with a 11-36 11 speed cassette (CX bike)

Ultegra 11 speed shifters
11 speed road-mtb cable pull converter
10 speed MTB XT mech
11 speed 11-36 Cassette.

I found with an 11-40 it was pretty terrible, pretty much has you describe, but I also found 1×10 with a range extended 11-40 cassette equally terrible!

That pretty much mirrors my experience of expanders. I’ve never yet seen one shift as well as an actual cassette.

I was just interested in a little reality check, really. If you lurk around forums long enough you hear of all kinds of strange combinations of parts that really shouldn’t work …