i was inspecting my discs yesterday, and i noticed on the inside face of one of my front brake discs, there is a wear groove about half way between the inner and outer edge. it is deep enough easily to feel with my finger nail.

any idea what would cause this? i haven't taken the caliper off yet (it is a 4-piston caliper), but inspecting it i couldn't see anything that would do this. the only thing i am thinking is maybe one of the caliper springs.

 

Could be a small stone or something.

Fish

 

Check the caliper mounting bolts closely to make sure one of them isn't rubbing the disc.

 

You didn't neglect changing your pads? Check those too.

 

nope, pads are pretty new, that's why i am kind of wondering.

small stone: hmm, interesting. but it seems a little unlikely.

mounting bolts: i quickly checked over that last night, but it is possible. i should mention though that this groove is very thin, not more than the thickness of a coin, but is fairly deep.

i might have to just pull the wheel and open the caliper/pads to take a look. i was just wondering if this is a common problem that someone might recognize.

 

If you have taken off your calipers in the past, you may have inadvertently installed the bolts incorreclty. There is one bolt that is slightly larger and if installed in the other hole, it will protrude out. During cornering the suspension flexes and the bolt will make contact with the rotor. I made this mistake and groved one of my front dics...