groove in brake disc
 

i think a rock trapped in the brake pad has created a deep groove in the rotor. can i get away with just cleaning out the rock from the pad and run the rotor as-is? it's a new rotor and because of the depth of the groove i don't think it can be machined.

I had a similar problem, groove was from the slide pins not being greased properly/being seized. You can try taking apart the brakes, cleaning + lubing everything, re-assembling and test-driving. If it drives fine/brakes without vibration I'd say it's good to go, otherwise replace.

Check the slide pins my guess is that one is seized

how would i know if the problem i am faced with is yours from a visual standpoint? the groove in the disc is in the middle of the surface, and it does not make noise without the brakes being applied.

front or rear? Newer mustang? If your cars newer, I'm probably wrong (seized slide pins are usually on cars that are a little older than yours)

Brake Caliper Seized :( - Ford Mustang Forums (post 7)

sounds like the stock rear pads like to seize/rust if you leave the parking brake applied in the wet. I'm just speculating, you'd have to take it apart to see what's wrong for sure

it's actually my dad's subaru. left front.

it just had been dealer serviced 2 months ago.

went through the brakes last night. turns out it was the right rear. outboard pad is okay, but the inboard one has been half-dragging on the inside face of the rotor and has made contact with the squealer. the center groove is completely gone. the slide pins are moving if i manipulat them by hand but all this evidence indicates otherwise. i had no grease, etc. on me at the time so i wasn't able to clean things up.

pics below are of the outboard pad (getting thin but okay), and the inboard pad (not okay...). the 2nd picture is terrible, but you can tell it's much thinner on the left than it is on the right?

i called some of the sponsors here and many want to replace the rotors rather than machine them because a)machine shop charges per rotor as much as it would be for a new one, and b)risk being too thin afterwards will warp?

i have another question: when i went around all 4 corners to check everything, i noticed that one the fronts has lost it's squealer. it looks like it has snapped off at some point, but the pads are more than good (was replaced at the last service). is this cause for concern?

Just replace the rotors they are cheap and easy to do on your car.