Originally Posted by
Iride01
Yes, when I over tighten my cup and cone bearings in my wheel hubs the axle turns less freely. If it's over tightened, then it's not tightened correctly. Not sure where you are goin here.
Not all of the tightness you perceive is going to necessarily be bad for bearing wear though. Remember that these same grade bearings used in the BB are used in other things that handle many times more stresses at many times more speed and in much more adverse conditions.
So it's not like Shimano tells us why they made it plastic, but they specify (in line with that part being plastic) the torque as very low.
The other source referenced above - aftermarket bearings supplier (
https://www.kogel.cc/products/shiman...-adjuster-bolt) even goes as far as:
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Installation
Thread the fixing bolt into the crank arm, adjust it until all the lateral play in the crank arm and spindle has disappeared. Back off the bolt a quarter or half turn to make sure there is no sideload on the bottom bracket bearings.
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Cartridge bearings are not for bearing lateral loads. I wish I could find somewhere official reasoning why Shimano first made the fixing bolt plastic (arguably to make it less likely to be overtightened) and then double length.