Originally Posted by Duragrouch

I wish, for the life of me, I could find where online, years ago, they had a superb explanation on bearing life versus proper preload. It was great, and has proven to be true for me. It makes sense, and explains why I was spalling cones and balls years ago when I would adjust the cones for just the tiniest bit of slack, based on dad's advice on bearings, "better a little too loose, than a little too tight". He used to snug tapered roller bearings on front car axle, then back off "two flats", so 120 degrees. I later learned this is way, way wrong, it results in bad roller edge loading, and he was an automotive engineer, but didn't have as much knowledge with regard to rolling contact bearings. Bicycle bearing loads are not huge, but the difference between loading almost half the balls per side and only a couple, makes a huge difference in wear. This is something I have experienced. Perhaps a high preload is not needed, just taking out the slack, but either way, it's much better than leaving in the slack, which, by the way, also stretches the seals radially. I torque my cap to specs, just like you said in metric equivalent, I could have guestimated it, but I have a microtorque wrench which makes it easy. The crank maker did include a plastic wrench, but if they only wanted people to use that, they wouldn't have made the interface a standard Allen socket, nor labeled it with torque value.

The biggest difference in durability has been with pedals; Cup and cone with tiny balls, proper preload has made a huge difference in durability, versus intentionally leaving in the tiniest perception of slack.

Just because knowlege comes from outside bicycle mechanics, doesn't mean it's wrong. I appreciate you noting that Shimano externals are not angular contact. But evidently some externals are. And taking out slack on straight radial bearings may help, I have to think about that, my guess is, with just a small preload, it still behaves mostly like a pure radial bearing, but the preload to one side, taking out the slack, makes it perform better.

I'll be curious about the wheel hub setup on my new bike, which is supposed to have cartridge bearings front and rear, so I wonder if the spindle just clamps axially to the inner races of each bearing, or if there is any side preload between inner and outer races across the two bearings?