[ember1205]

Originally Posted by ctrlz

Warping of brake rotors is a misnomer. You would need the heat of Vulcan's forge to warp them.
What really happens is DTV or disc thickness variation. This is basically caused by rotors being mounted slightly crooked. Maybe dirt or rust between hub and rotor or torqued improperly. Anyway the misalignment allows the brake pads to catch the edges of the rotors and wear them unevenly. This happens even when pedal not applied. I think even like 10-20 microns of uneven runout can be sensed as pedal pulsation.
Best advice is to make sure mounting surfaces are super clean when you put on new rotors.

It's a misnomer in the sense that rotors generally don't "get warped" and then stay like that. They can, and do, develop irregularities across the surface when they get hot from use, but then tend to 'settle back down' as they cool. These changes are typically pretty minor overall.

When the material thickness of the rotors is near the minimum, ESPECIALLY if the two surfaces have different thicknesses from each other, the material can develop irregularities along the surface under load that are more pronounced. Still, this is likely to still be on the generally more insignificant side.

The biggest concern is likely due to simply not having enough material to absorb the heat properly from braking and the brakes either "fading" or outright failing during use (much like what can happen to trucks on steep downhill grades when they brake too much).

I believe the misnomer you are referring to is people referring to pad deposit / buildup on the rotors, creating pedal pulsations, as having a warped rotor.

[cdb95z28]

Yep, "warping" is not what is happening. It could be a poorly mounted rotor/wheel due to corrosion/dirt at the mating surfaces or most likely, uneven pad transfer on the rotor. Uneven pad transfer layer is very common and can be resolved with a simple light cut or honing tool:

https://www.amazon.com/dp/B007INTEMC...?ie=UTF8&psc=1

Here's some reading on the two types of friction that is utilized on brake systems and the role of the transfer layer:

https://www.cquence.net/blog/abrasiv...%20the%20other.

And some reading from Centric that defines transfer layer and proper bed in:


https://centricparts.com/getmedia/bd...c-8-2018_1.pdf

https://centricparts.com/getmedia/b6...y-8-2018_1.pdf


https://centricparts.com/getmedia/6c...k-8-2018_1.pdf


https://centricparts.com/getmedia/fd...e-8-2018_1.pdf

https://centricparts.com/getmedia/23...FAQ-8-2018.pdf

https://centricparts.com/getmedia/a0...l-8-2018_1.pdf

[cdb95z28]

I'd also note that some wheel cleaners are so aggressive that they can remove the transfer layer. This causes an uneven transfer layer. MeGuiar's Hot Wheels purple wheel cleaner will remove the transfer layer. I found that out years ago.