Ok fine, I get it. You’ve all read that http://www.stoptech.com/technical-supp… article and now you’re all brake wear experts. Cool. Let’s not discount the merits of that article, it really has some good information. But let’s stop with the bullshit.
Maybe rotors warp and maybe they don’t. That isn’t the point here. The point is that rotors are generally measured for runout and thickness variation if they’re suspected of causing a vibration. Whether the problem is deposits, hot spots, or (god forbid) warping, one of those two measurements is how you’re going to make your diagnosis.
Let’s assume the problem is deposits. 99% of the time you won’t be able to see them. So you measure and find both runout and thickness variation. In my experience, you can’t make this go away just by doing a few (or even quite a few) hard stops to “scrub” the material away. It just gets worse or doesn’t work at all. The only times I’ve seen this work is if it’s just light surface rust but that usually causes more noise than vibration. So it comes down to resurfacing or replacing (pads too).
What if the problem were hot spots? You can almost always see these, especially if you know what to look for. But it’s still a good idea to measure. So you do, and find both runout and thickness variation. Huh. Just like with deposits. But you can't machine these out. So it comes down to replacing, pads and rotors. Just like with deposits.
And if those rotors are actually warped? They will look fine to the naked eye (grooves and lips don’t necessarily indicate problems, just normal wear). Just like deposits. Weird. So it comes down to resurfacing or replacing.
Resurfacing is very much hit or miss and rotors are usually cheap enough that they outweigh the pros of resurfacing. So let’s just replace them. And for the sake of this whole spiel, let’s assume wheels have been properly torqued and the hubs are clean and true.
So how do we differentiate between deposits, hot spots, and warping if we can’t see any problems? Beats me. You certainly can’t make that differentiation in most shops, garages, or driveways. Even the correct repair is the same. Trying to make that differentiation is not worth the effort. Trying to explain the difference between those three problems to your customer, mother, brother-in-law, sister, best friend is not worth the effort. Saying the rotors are warped is a general and all-encompassing term.
If we’re really going to argue semantics every time someone says their rotors are warped, then we as automotive enthusiasts and professionals have a lot of work ahead of us. Let’s start punching the idiots who refer to engines as motors, since motors are electrical components. Let’s put dog crap on the hood of the car of anyone who says their car threw some faults and the CEL came on, cars don’t throw things and it’s technically a MIL (malfunction indicator light). And anyone who refers to a crankshaft position sensor as a CPS (it’s CKP, camshaft position sensor is CMP) we can force to only read Alissa Walker articles and use public transportation.
Stop the bullshit. Stop arguing semantics over warped rotors.