This is the scoop on knock offs as far as I know----
Knock offs were used in racing many years ago because they came off with
the beat of a hammer (eared type knock offs) and were replaced with the
beat of a hammer. When trying to do this quickly, there is a great chance
of cross threading the knock off on the hub. SOOOOO (I AM getting to the
point) consequently, the knock off is made of a softer material than the
hub. This is so when they get cross threaded for whatever reason, it does
no damage to the hub, just trashes the knock off which is easily replaced.
I put my knock offs on there just as tight as I can without doing damage to
the knock off. You avoid the infamous clunking, and preventing excessive
wear due to slop.
"He who sheds his blood with me today, shall be my brother."