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Top, not bottom:
tl/dr
Shimano or Campag. -
where is @Skülly and what have you done with him?
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Not sure what the difference is
Higher clamping force. The theory is that off centre axial loads on the wheel which want to rock the lock nuts on the dropout faces and splay the fork ends apart can do so if they exceed the preload generated by skewer tension. While this isn't technically wheel flex, it has the same effect because the fork flex allows wheel displacement, which makes the brake rub.
Not sure what the difference is, @Turkish, can you enlighten me? No technical drawings required...