Originally Posted by sdowney717
Originally Posted by Cujet
It's good to know that if a rotor warps when hot, it's going to warp when hot after it's been turned.
One thought is that the recycled metals are distributed unevenly in the disk. Another is uneven cooling, the metals in one location were "tempered" by a red-hot stop, then keeping the pads clamped on that location while the rest of the rotor slowly cools.
Regardless of why it happens, "IF" you experience heat related warping, replace the rotor.
https://www.onallcylinders.com/2017/05/19/6-biggest-brake-rotor-myths-debunked/
Rotors do not warp. I am a mechanic. It is a myth. I did turn one badly once and since it was not true it pulsated and had to get re-turned.
https://www.brakeandfrontend.com/warped-rotors-myth/
https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3043065/1
https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3895543/all/Brakes_Rotors_DON'T_WARP__-__A
Brake pulsating is usually hard deposits on a rotor instead of warping, but they do in fact warp in a small % of cases. This is usually due to excessive lug nut torque and/or driving like a madman with hot brakes then going through a water puddle to rapidly contract them.
In fact it is very easy to see on a lathe when it starts cutting into opposing sides instead of evenly, or just using a high precision flatedge against the surface.
It is funny when an almost-myth is countered with another myth. Rotors do warp, but that's far less common.
As far as turning rotors off vehicle, it had worked fine for me for many years, but then they started making rotors thinner so there is often too little material left to bother, which doesn't make on-vehicle any better, and access to lower prices online made it even less cost effective.