> Most of the _guesses_ are so far off the wall that you couldn't play
> handball with them, but this particular explanation is very close but
still
> not quite complete. In fact the cause of self tightening has nothing to
do
> with the construction of the wheel being a wire wheel, as the center lock
> alloy wheels will do the same thing. And the self tightening action in
> fact _depends_ on a small amount of clearance in the splines so that the
> parts can move slightly if the nut is a little loose.
I think the chicken and egg are the wrong way round here -
There must be clearance between the internal and external splines, else the
wheel would not be able to be assembled or removed from its hub without a
press or similar.
Because there always must be an assembly clearance, and therefore there will
always be some relative rotational motion between the inner and outer
splines which could lead to loosening of the wheel, the rest of the mounting
system is designed it ensure that this won't happen - hence the 'handing' of
the knock on(off) threads.
The self tightening design is an outcome of the need to have some clearance,
rather than the clearance being provided to ensure a self tightening action.
Just a minor point, but the reason for the clearance is often overlooked.
Cheers Ian f
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