Q: Warped brake rotor--what causes that and how to repair

You need to change both. My advice is not to have them turned because if you have rotors made out of steel and they warp, and you turn them the other way to make them flat then they are thinner. They already warped once and they are going to warp again even faster.

So just replace them with new rotors and brake pads. They are not all that expensive.

The only difference between expensive and cheap pads is that cheap pads will make noise but with brand new rotors, they are not going to make any noise. So you don’t have to spend that much doing it. And the reason they warp is because heat just eventually builds up and they get so hot that they warp. So you’d want to check the things like if the master cylinder is sticking out, if the caliper is sticking out, are the brake hoses collapsing. Because if they keep warping, it means that for some reason the brakes are running sticky on and getting too hot.