It’s a good question. My pea-brain reckoning is the metal near the stud & nut may deform from over-tightening, resulting in the corresponding surfaces are no longer absolutely flat. No need to guess, this could be proved by placing bolts through the existing holes an old rotor (one verified to be flat), over-tightening the lug-nuts, then measuring if the rotor surface remains flat using a straight-edge.
That’s the common sense practical method; i.e. why re-invent the wheel? Sometimes it’s fun to see if you can reinvent the wheel though.
I believe that over tightening the lug nuts leading to the rotor warping is a myth, 100% myth. Somebody, somewhere who had some following as an expert came up with this as a theory and no one has questioned it. The lug not does NOT contact the rotor. The rotor is sandwiched between the wheel and the hub, two large flat surfaces.
Over tightening the lug nuts would damage the lugs first, the wheel second.
One possible exception, in the early days of disc brakes, the rotor and the hub were one piece and it was cantilevered over the wheel bearings. Maybe, over torquing the lug nuts in those day could have led to a warped rotor, but not when the rotor is clamped between two flat surfaces
“Over-torqueing the lug nuts does not affect runout immediately. However, as the rotor heats up, the uneven clamping force of the lug nuts causes the rotor to expand unevenly. This will eventually lead to pedal pulsation caused by the excessive runout.”
I’m just not sure I understand where the “uneven clamping force” comes from if they’re all overtorqued, but they’re the same torque.
Whatever, does not matter to me. I’m not trying to argue with brake experts. Just trying to understand the theory behind it. I still don’t. But, I’m kind of over it.
I’m guessing part of the explanation is that just b/c the lug nuts are over-torqued doesn’t imply they are all equally over-torqued. Perhaps if they are all over-torqued the exact same amount this would be less of a problem.