Hi,
from what I understand…and cycling industry loves to just throw in new standards…
T47 inboard measures 86,5…now, surprise, if you ever had to install a t47 86,5…you might have scratched either your
head or your frame, because the flange where you engage your tool is very thin.
So…they came up with a bb-shell width of 85,5mm…so a dedicated bottom bracket t47 85,5 has a wider flange for tool engagement!
That means you end up finally at the same total width.
Now…of course you can thread in a 85,5mm bb into your 86,5mm frame….but…you will end up 1mm wider!
So…whatever crank you are going to install….it could work…but you should consider it.
I hope I am right and it makes sense…