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Drums and rotors do in fact warp. As others, Ive spent enough time behind a brake lathe to know that. Anyone that says they do not warp have no idea what they're talking about. Min thickness is listed on the rotor, you make your cut then measure.

Flywheels warp too, so do clutch packs.
 

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I have, although it's not as obvious to the eye as you might think, especially with metallic pads. Pulsing brakes are a classic sign of this condition. Mine originated with an emergency braking situation and actually got worse over the next months.
Let me preface by saying (again) Ive worked on many cars/trucks. Also ran a fleet of 18 vehicles (which itself is another ballgame) But if what you and that web page are saying is true, rotors would all warp before they wore out. Which is not true. 99 times out of 100 the reason for warped rotors is heat. Riding the brakes, bad caliper, line or pins, etc. The vehicles in my fleet would run 500-800 miles per day. Id install probably 5-6 sets of pads on the same set of rotors without any warping (or the mysterious buildup as you say). Just tossing the rotors from wear.
And this wasnt in fly-over country USA, but NY/NJ with plenty of traffic.
 

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I'm guessing 9 years as an OEM brake engineer doesn't count for much compared with all the "experience" posted here but you simply can't get rotors hot enough, with normal usage, to metallurgically cause them to warp. But we really didn't bother testing the really cheap crap so I cant disagree with all the experts here!
"Heat" meaning excessive heat from a bad caliper, line, pins, etc. Will in fact warp a rotor.

I had a problem with the ABS module on a E250 van not letting all the pressure return after braking, warped brand new rotors.
 

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It does happen to an extent, I believe it's why we end up seeing the glossy finish on rotors and while it may account for some thickness variation, I've had enough rotors on a lathe to also see that metal gets removed not just adhered friction material to get a rotor flat again.

Mostly when I see pad material fused to a rotor it's because a vehicle hasn't been driven and some sort of reaction happens between the friction material and the rotor leaving a noticeable build up(real common on 07-16 Honda CR-V rear rotors). As a professional tech we would just resurface them but realistically you could grind the build up off with an abrasive disc on an angle grinder. Not sure how long that fix would work/last though.

The other thing I have noticed when they do leave a build up from sitting, even when you resurface them you can get the rotor flat but still see the outline of the brake pad where the build up was.
Glossy finish is glazing. Again, from misuse or excessive heat (faulty components).

If you guys can come up with more than one dumb website saying brake pad material transfers/bonds to rotors/drums I may believe you. But for now and from my long term experience, its b.s.
 
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