2021 GT the rear brakes squeal only when backing up. Have 15,000 miles on it has done it for a long while thought it would go away but hasn't. Any ideas ?

 

There could be numerous reasons why. If you are still under warranty take it top the dealer. If out of warranty go to a place like Firestone for a free brake inspection.
Brake pads will get a pattern of wear primarily from the forward movement of the wheel and braking. Baking up is changing the the wear direction and can cause nosie.
Other things would be a possible warning of mechanical issues and that is why you should get your BRAKES INSPECTED.

 

It is still under warranty, would the brakes be covered ??

 

that depends. Generally not unless they find a defective part.

 

Agreed. Had this happen on my Acura a couple of years ago and it turned out my brakes were shot and even getting into metal on metal. Only way to know if something is wrong is by having them checked...

 

There is plenty of lining on my pads, I can see that when the wheels are off.

 

I'm wondering if it's just something caught in the brake dust shield or something, but it's really gonna need that inspection.

 

Brake pads are usually inexpensive. You could upgrade them to some Akebono, EBC or some other kind of quality ceramic pad. I say this because you appear to have enough mechanical knowledge to get the wheel off and inspect them yourself. You are only 2 screws (and possibly a piston retract kit) away from changing them at that point.

If that's too much it might simply just be glazed. A brake shop can resurface the disc and probably sand the pads and that should also take care of it for a while at least.

 

Remember to do the proper rear brake service procedure as to not damage your braking system.

DO NOT SAND BRAKE PADS !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!

ASE