Originally Posted by
choddo
Unfortunately this is a hollowtech ii crank but the bearings are internal threaded T47. Like trying to get hold of a jelly.
Haven't worked in a shop in decades, but the impression I get from T47 installation videos is that Shimano deliberately designed the notches on those outer cups the way they did to make it difficult or impossible to overtorque them (maybe worrying about home mechanics without torque wrenches). They could have made the outer surface of the cups octagonal, for example, to make setting the torque easier. Just guessing, though.
Kind of the way Suntour used plastic stem caps on the first AheadSet generation to keep mechanics from over-tightening the stem bolt.
But customers and mechanics jumped to the conclusion that Suntour was just cheaping out on the part and demanded metal stem caps.
Suntour said, "Fine; Have it your way" and went to metal caps.
Back to the T47 cups, though: just looked, and Shimano specifies min. 35/ max. 45 Nm. I'll check mine. They're almost certainly not tight enough by that standard.