Took car to dealer for an inspection. They say my rear pads are due for change and they can resurface the rotor.
Took it to a local mechanic for a second opinion. They say the rotor is too rusted to resurface and recommend replacing the whole thing.
What should I do here? Resurface or replace.
Too rusted? It's the wear surface you are worried about not the little bit of rust on the outer edges or on other areas of the rotor. For that reason, it is NOT TOO RUSTY to have it resurfaced. The main reason why you cannot resurface a rotor is if the wear area is too thin. There is a minimum thickness they need to be AFTER resurfacing. Even if the contact surface is rusty, you can still turn them, getting rid of the rust. If they are still thick enough after this, they are still good.
With that said, there may be other reasons why you would want to just replace the rotor rather than have it surfaced. Any which way you do this, you should have a fresh surface for the brake pad to ride on versus a worn one. I'd have to say, the contact surface on your rotor looks might good.
NOTE: If I were in a pinch, I'd deglaze these and run them again ... that's me, though (and I can't see both sides, so there may be something there).
Typically, for best results, having a fresh machined surface for the pad to do it's work against is your best bet. The only way you can do that is with a new rotor or getting it resurfaced.
The major downside to resurfacing is you're taking metal away from the rotor. This makes it so you have less mass, which means it's less of a heat sink, which means it can't absorb as much heat. Why does this matter? Because the way the brakes work is by turning the rotating motion into heat by the friction of the brake pad itself. If you can't collect, then remove the heat as well, it becomes less efficient at doing the job.
Usually, when you do your own brakes, buying a set of rotors costs just a little bit more than having the resurfaced. If you figure what your time is worth as to taking the rotors down to your nearest shop which will turn them, wait for them to get done, then bringing them back home to put them back on ... that's a bit of time wasted. Most shops can turn the rotor on the vehicle, which would save you time, but then becomes more expensive, because they are doing the brake job. Just buying new rotors in the first place saves a lot of time, because you're doing at your convenience and not at the convenience of the shop you take it to.
If you are having a shop do the work, it about becomes a wash. They have to do more work when turning the rotors versus just putting new ones on. You'd have to check for sure at the shop where you want to get the work done as to which way is better for your pocketbook.
