Hello I have a 2006 Impala SS 161k miles
About 2 months ago I had a mechanic replace my brake pads both front and back.
Now the passenger side rear brakes are making a metallic grinding noise... I heard no squealing noise that usually comes with wearing brake pads. Looked at the rotor and there a clear signs of grinding. As well as brake dust/metallic dust on the rim. So I would assume the brake pads are bad.
But how would they get this bad this fast to the point were its grinding the rotor?
Why would only one set of brake pads go out just like that? The rear brakes at that?
Looking at the pics, it appears that the pad is worn all the way down to the rivets. Or at least down to the sensor.
Several thoughts on this...
One is that you have a bad master cylinder, but I doubt that's the case. If it fails to suck the piston back when the pedal is released, you could get accelerated brake wear, but I would expect that on more than one wheel.
Two would be that the right rear brake was not bled properly and has air in it which is causing the pad to ride on the rotor thus causing premature wear.
Three would be that the glide pins are sticking, causing the caliper to be biased to one side resulting in one pad wearing (much) faster than the other. (The piston side pad releases, but the other side doesn't move much and rubs the rotor.) I've also seen where too much grease was packed around the glide pin which can also push the caliper to one side.
BTW, Do you see any signs of brake fluid leaking?
My take is either 2 or 3, both of which can cause one pad to get worn while the mating one still looks new. I'd put a new pad on it, bleed it, and inspect the glide pins, making sure the caliper can move freely both ways.
One last thought - what kind of pads are they (ie, material)? Cheap pads can wear extremely fast if there's an issue as described above. You want to be sure your mechanic didn't tell you one type, then put some cheapos on instead.