markz said:I got no clue but just maybe the pressure of the nuts push something inwards. Thats my guess.
You would think, but looking at the axle I can't see how that could be. The axle is one solid piece. I guess it just makes a perfect acoustic path for the sound to travel when tightened. But it has to be really tight before it makes that acoustic path, which makes me think that it is something else with pressure.