Odd brake pad wear in one spot - pic included

[hywy61]

I have an odd spot on the brake pad. See below. What could be causing this?

Pic on the left with the arrow is outside pad - passenger front. Other pic is inside pad WITHOUT the same odd wear spot.

I have a grinding noise when applying brake at low speeds. It doesn't happen each time i stop though. Maybe every 5 stops.

I have about 3mm on the pads so they are due for a change. Rotors are fairly worn and old.

Just trying to determine if this could be a caliper issue? Both seem to be retracting smoothly when i re-assembled the brakes.

thanks in advance.

 

[cdansan]

That does not look like wear to me. It looks like a piece of friction material broke off.
Time for pads and rotors.
Dan

 

[discostew]

That does not look like wear to me. It looks like a piece of friction material broke off.
Time for pads and rotors.
Dan

I was thinking the same thing. It looks like damage and not wear.

 

[hywy61]

Not sure how that would have happened but it makes sense now why the grinding noise happens periodically. I guess little pieces are occasionally falling out.

 

[Gripen]

Possible micro fracture developed during use, some sort of defect/inclusion that was there when that individual pad was manufactured, or a number of other things that may have caused the small chunk of pad to be missing.

I once had an old Toyota that had a rattle coming from one of its front calipers. Drove me nuts. Thought it might have been this or that. Pulled the caliper, removed the pads and found that one of the pad's friction material (half of it, anyway) had completely separated from the backing plate. Cue "Well, wasn't expecting that."

 

[hywy61]

So i replaced the rotors and pads yesterday. Same exact odd wear spot on the drivers side. Pic above was passenger side. Very odd.

I thought for sure that was the source of the grinding but that didn't fix it. Its not a loud as before but still there. At low speed when i apply the brake I hear it. Once i release the brake and drive on it stops. I am stumped.

I would think a bad caliper would not retract and i would hear the grinding after stopping and attempting to drive again.

 

[helievacpilot]

If it is coming from the brakes, you've eliminated pads and rotors. That leaves calipers. Re-build or replace.

 

[hywy61]

That would be logical. What causes the grinding noise though when applying the brakes? I don't understand how a bad caliper could do that.

 

[helievacpilot]

That would be logical. What causes the grinding noise though when applying the brakes? I don't understand how a bad caliper could do that.

Just a thought, but maybe the two pistons aren't applying the same pressure causing the pad to chatter a little bit on the rotor? Hard to tell.
Also, your saying that the opposite side pad has the same small chunk out of it as well? If that's the case, it would be extremely hard to believe that two different pads would have the exact same defect.
Have you double checked that you've got the correct pads? If so, I am definately leaning towards calipers.

 

[hywy61]

Definitely had the correct pads. I had 25 k on them with no issues until now. Just odd how those would both wear like that in the same location.

One of the seals around a piston was torn so maybe dirt/dust had gotten in there and it's no applying evenly? Had to imagine that would cause a grinding noise. I would think the pads would be worn unevenly if that were the case.

What about the caliper slides? I greased them again but maybe they are not sliding smoothly. Can't imagine that would cause grinding.

 

[helievacpilot]

Definitely had the correct pads. I had 25 k on them with no issues until now. Just odd how those would both wear like that in the same location.

One of the seals around a piston was torn so maybe dirt/dust had gotten in there and it's no applying evenly? Had to imagine that would cause a grinding noise. I would think the pads would be worn unevenly if that were the case.

What about the caliper slides? I greased them again but maybe they are not sliding smoothly. Can't imagine that would cause grinding.

If the guide pins or bores are worn, it's conceivable the calipers are "twisting" as un-even piston pressure is applied. Just a thought.