I had new tires put on yesterday and when I went and picked up the car, the shop told me that one of the rear pads is down to metal probably because of a stuck caliper. I've replaced pads before on cars, but never a caliper. How can I troubleshoot to make sure that a stuck caliper is the problem? Will this require a replacement caliper, or are they things to try to repair the caliper? Are there any other causes of a prematurely worn pad besides a caliper sticking? *update* I pulled the wheels off today and replaced the brake pads and looked everything over. I'm a little uncertain on a couple of things, hopefully someone has some advice. The rear passenger side was the problem. The inner pad was nearly to bare metal, while the outer pad showed about 50% wear, consistent with the drivers side pads. The calipers on a Milan have a piston on the inside of the rotor, and the pad on the piston side was the overly worn pad, so I assume this means the piston was not retracting properly? I lubed the glide bolts, but they had visible grease and I didn't note any other visible signs of disrepair. I will have to special order the caliper assembly, as no one stocks it, so I'm wanting make sure that is the problem before I do so. Could there be any other cause here other than a malfunctioning piston on the caliper? Do the glide bolts actually do anything mechanical that may be the source of the issue? One other issue, the new pads appeared to have a thicker shoe, and when I reinstalled them with the OEM shims, the wheels were hard to spin. I drove the car for a couple of miles to see if the pistons would readjust but the wheels still were harder to spin than I believe was normal, so I removed the shims. The wheels spin better now. Is this common? I read that on some better pads, that the shims were not required, but these were just some $34 Gold pads from Autozone, nothing special. Advice?