Hello,

On a non-boost frame with 73mm BB shell installed a BB-MT801 bottom bracket and a FC-M7100-1 (172mm non-boost with 52mm chainline).
As per the instructions I put one 2.5mm spacer on the driver side.
Now the safety pin on the crankarm wont engage the hole in the shaft, the shaft not protruding enough.
I guess it is a tolerance issue, but don't know how to proceed. Should I get a thinner spacer like the 1.8mm included in the MT801-K package? Unfortunately the normal version comes with 3 pieces of 2.5mm spacers.

Thanks

Did you tighten the cups enough? 35 - 50 N-m or about 25 - 37 foot-lbs. You've double checked the shell isn't a little over 73mm haven't you?

What was on it before?

Did you tap the right crank with a mallet to insure it is fully seated against the spacer and right cup?

Rubber mullet was used for insertion, and also tried overtightening the "preload screw" a bit hoping it would pull everything in place.
Shell measurement seem good, but the measurement tolerance might be worse than the tolerance required by the crankset, idk.
I thighten everything with proper torque, even my water bottle cup
I tried reinstalling 3 times (with brackets and everything) just to make sure

Finally I got a 1.8mm spacer (luckily my other bike has the 0.7 + 1.8 spacers so I could swap) and now it is good.