My Dad'* Regal was making a grinding noise when the brakes are applied and there was some pulsation. I replaced both front rotors and pad (Wagner Thermoquiet), relubed the front caliper pins and the rear caliper pins. The pulsation is gone, but the grinding is still there. It only happens when brakes are applied (soft or hard). Otherwise, braking is fine. The old parts, front calipers and rear components all look normal to me.

Any thoughts? Should I replace the rear pads & rotors? What about the calipers (like I said, they looked OK).

Thanks.

Any chance that the car hit a curb hard or anything else that could knock something out of alignment?

Does the grinding sound come from a particular wheel?

I don't know whether a curb was hit. Would the noise only come when braking, though? Driving alignment seems to be fine.

I can't tell exactly where it is coming from, but I'll try to hear next time I drive it. I was thinking that the rear rotors may be warped?

Grinding is usually some foreign material getting in between the pads and drums or rotors such as dirt or brake dust OR the pads are worn down the the rivets/metal. You can isolate it to the rears by using only the emergency brake to stop.

i would also look into the possibility of one of the backing plates touching the rotors

To clarify, this is the backing plate for the rotor, right?

correct, rotor or drum, whichever applies in this situation

can you confirm whether the sound is coming from the front or rear?

yes, but to my thinking it would grind all the time if that were the problem.

I'm wondering if you might have a bad bearing that shows up during breaking because the weight of the car gets transferred forward

both are very reasonable options. very often a backing plate will only grind when the brakes are applied. Singscountry had a problem similar to this a while ago. I find it LESS likely to be a bearing due to the brake dependent symptoms, but still is very possible

I have had this exact problem in my 2007 Buick Lucerne for 2 years plus in my front drivers side wheel. I have had it diagnosed by 5 mechanics resulting in replacement of all rotors, pads and left front wheel bearing. The last three mechanics were certain that it was the rotor backing plate scraping on the inside of the rotor. It only scrapes when I brake, sometimes slight, sometimes really bad. They fixed this for free by just bending the plate. But one block out of the shop it was no better. I have spent more than $700 on brake jobs and other.
If it were the backing plate it would seem to me that it would scrape continuously as both it and the rotor do not move. I am considering removing the backing plate altogether. Would that have any issues?