Rule of thumb aside, on factory alloy wheels VW used nuts that didn't
even come close to meeting your "stud is flush or protruding" goal. A
mere 7+ threads was deemed sufficient by one of the worlds largest and
most successful car maker.

Mark

Dick Wong wrote:
> General rule of thumb for bolt to nut engagement:  From a strength
> standpoint, the minimum length of thread engagement should be at least the
> diameter of the bolt.  For a 14mm x 1.5 lugnut/lugbolt, you should go for
> 14mm of engagement.  If you can't measure the available thread length, you
> can calculate the minimum number of turns needed by knowing the thread
> pitch.  In our case, the thread pitch is 1.5mm per thread.  The nominal
> bolt diameter is 14mm, therefore 14mm/1.5mm per thread = 9.3 threads.  And
> since there is one thread engagement for each turn, the minimum number of
> turns is 9.3 for the nut/bolt engagement.
>
> In the case of a lugbolt engaging into the brake drum, if the drum wall
> thickness is less than the bolt diameter, there is no further strength gain
> by going beyond the depth of the available threads.
>
> If nothing else for a nut on a stud, make sure the stud is flush or
> protruding from the top of the nut.
>
>