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Interesting about your service course experience.
How do you mean "external difference in chain dimension externally between 11 and 12 speed. It was internally that it was different."?
I've heard some stories of teams experiencing chain drops during the era of mixed groupset, but some others saying that was actually the first batch of 12 speed derailleurs etc being trouble.
gp700-
I can't tell you specifically as even with a few of us taking a micrometer to the links, we only noticed narrower dimensions. Shimano techs told us that the outer link dimensions were never changed between 11 and 12 speed, so in theory, there's little to distinguish them; Shimano made the change to the inner dimensions of the chain in order to operate smoothly with the narrower 12 cassette sprockets.
Dropped chains during that era were no different to any other in my experience. The worst dropped chains were with Oval rings and mis-shifting was with oversized jockey wheels.
I'd like to say they're marked as 11 but they're 12, and to my limited experience with some measuring tools, they seem to be, but I really don't know.
Chak
Simple answer is, you’re bang on and that’s why I had difficulty selling it on eBay.
I’ve measured this to be as you’ve said, 12s compatible, but it was hard selling it as such with the markings for 11s.
Now this was part of the recall for the 8000 era chainset. But the only returned the 8100 era stuff, which is 12s.
I worked as a service course mechanic a short while during the 11/12 speed transition, and we were advised by Shimano that they're interchangeable as there was no external difference in chain dimension externally between 11 and 12 speed. It was internally that it was different.
Which brings us to this chainring set, how do I advertise it, 11 or 12 speed compatible?
I’ve personally used these on both 11 and 12 speed groups and I’ve notes zero difference in shifting.