thats the new thing now,GM froze the bores on their diesel,and it stabilizes the metal.We had hardened bearing (roller) grow a 1/32 before shipping.these bearings were heat treated and quenched,and ground to size.
Metal is some strange stuff.
I'm happy with my replacement rotors,that and using ceramic pads,for a year,no ground off metal.No warpage either.
so any way with the bearing we started freezing them.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran