Groove Found on Brake Disc

For quite sometime now, I've been getting squeaking noise from one the
brakes on the rightside and when I decided to give it a look, I found
this one noticeable groove on the front right brake disc. All the
other discs are smooth as glass, with no noticeable surface grooves or
distortion at all. The groove is about a quarter of the way in from
the outer edge of the disc and it must go all the way around since I
can see it at the upper portion of the disc and the lower as well. And
I don't know if this makes sense, but the inner part of the groove
looks to be smooth as well, not rough.

The groove isn't that deep nor that wide at all. But I can certainly
see it and also feel it when I run my finger over it. (Oh, btw, if you
ever need to touch your brake discs, make sure to have had parked your
car for a while before doing so, unless you like squealing like a
little girl. People think you're a weirdo when you make this noise
hunched over one of your tires in a parking lot.)

I'm wondering if it's possible that a very small rock or debris had
been caught between the disc and the brake pad and that was the cause
of this groove? If that's the case, perhaps it's possible that the
debris might be embedded into the brake discs since I'm getting this
squeaking noise when I apply the brakes at relatively low speeds, say
below 25MPH (40KM/H)? And yes, I get the noise even when the car's not
"cold".

I'm taking my Pilot in for one of its scheduled service next Monday
and I plan to show the groove to the service advisor and see what he
says. Just in case he writes it off as being nothing to worry about,
despite the brake squealing, what are some of the points concern I can
present to him to get him to have a technician inspect the brakes
thoroughly? I mean, a groove forming on a brake disc isn't normal, is
it? Thanks for your time and input.

 

That sounds like the worn pad indicator. It drags across the disk and
makes an awful shrieking noise when a pad gets thin. You can get a good
look at the pads by removing the tire.

 

Steve Lee said for all posterity...

Yeah, I already did this once, but at least no one was around to
witness the act and the aftermath.

It's funny you mention that. A few weeks ago I heard an awful
scraping sound coming from the vicinity of my left front wheel. I
was driving slowly (less that 25 mph) with the windows down, and I
could here the sound echoing off passing cars.

When I found somewhere to pull over, I couldn't see anything wrong.
I got my son to back the car up just a little while I stood near
the wheel, and it appeared like something small (piece of gravel?)
fell out from between the pad and the disk. I couldn't find
it on the ground, but the noise was gone when he drove it forward.

I've never had this happen before with any car I've owned.


Casey