My rear brakes started squealing a while back, so I purchased new pads to replace them before they would get too low and trash the rotors. Well, upon inspecting the pads through the inspection hole on the calipers, they didn't look low, so I didn't get around to changing them. Today I heard a nasty grinding noise coming from the right/rear wheel when slowing to a stop at traffic lights. I pulled the pads tonight and they're low, but not completely gone. On the passenger side, there is uneven wear. The outside pad has some meat left on it, but the inside pad is really low. The pads on the driver side rear have plenty of meat left and are evenly worn.

The question is, what could be causing the grinding noise? The inside passenger side pad is low, but not completely shot. There are no blatantly visible grooves or scratches in the rotors. Before removing the tires I checked for worn wheel bearings by grabbing either side of the wheel and giving it a good shake. There was no play on either wheel. The grinding is only there when I have the brake pedal depressed, at low speed as I'm slowing to a stop. I don't think it's drivetrain related, b/c it happens whether the clutch pedal is in or out and whether I'm in gear or in neutral.

Oh, and one thing of interest is that there were no shims backing the pads when I pulled them off. Previous owner must have lost them.

Any thoughts?

Well the uneven wear is probably caused by the caliper seizing up on the bolts. A little more grease for the almost 20 year old car. As for the grinding, did the pads have one of those little metal warning tabs that is supposed to hit the rotor before the pad material runs out?

Also I'm unclear on this, is it grinding with the new pads in as well?

I have not installed the new pads. I have only pulled off the old ones (car is on jackstands right now). I did not see metal warning tabs. One thing to note now that I think about it, is that the grinding sound was not constant, but an oscillating sound. I'm wondering if the rotor is warped and making contact with...something. I couldn't find any visible signs of wearing/grinding on the rotor/caliper/wheel, but I'll take another look tonight.

Something else you can check is for clearance between the rotors & dust shields. I had a similar problem where a sound was only audible during slow breaking, which turned out to be a slightly pushed in dust shield rubbing against a warped rotor making the same oscillating sound you described.

Good thinking. I'll take a look at that as well. Thanks!

On the caliper that has uneven wear, check the guide pins if they are frozen or kinda hard to move. Remove them and clean them up and lube them. If the guide pins move freely you'll need to change the caliper(or rebuild) cause the piston is stuck and causing the inside pad to make contact with the rotor and wear out the inner pad.