Rear pads metal strip

You talking about that chrome piece or gold piece That's the wear guide it makes a squealing noise when the pads are worn down to the level of that metal bar on that one pad which kind of doesn't make sense I generally pull those off when I install the new set of pads because I'm going to not rotate but I'm going to change them out way before they get anywhere near that mark they'll get overheated or be old enough to just change before I get to that mark or that strip

SM-A715F ?

 

That metal strip is copper (or some sort of copper alloy), and it's purpose is to make noise when the pad is near worn out.

Can you post a pic of the "uneven" pad wear? Also of the rotors, both inside and outside if possible. There is a narrow zone of the inside face visible without disassemble.

Are you cognizant of the need to align the piston so that the spike pattern is like an "X" (so it "straddles" pin on inner pad backing plate)? LIke this:



Brake info from Repair Manual attached:

 

You've got to pull the slides out of the boots clean them off degree some completely re-grease them You can buy new boots if you want and new slide liners tap them in You're good to go That's what's making your uneven pad wear is the pins are sticking halfway in or out they should slide like butter if they don't it's no good really clean and do it again use good green grease that water and what nonsense will not remove

SM-A715F ?

 

That's okay You put one finger on the slide and you push it in it should go in like butter remove your hand if it comes back out that's A okay. No problemo when you have it all back together they will center and do what they're supposed to do Make sure you have all the original chrome clips and everything in place You can buy them from your brake parts manufacturer for about $12 for a whole bag of them they need to be there if you're leaving them out these are not allowing your pads to float in the clips and truly float if those clips are missing they're all sitting at the bottom of their tabs they were there for a reason not to be omitted for home ingenuity

SM-A715F ?

 

I don't know where you are I think you said further up no problem I'm a foreigner to living in North Carolina USA personally to me those paths look like pure hell pads like that in America cost like $12 a set I buy pads that cost about $26 a set made out of modern materials etc so I'm not sure the benefit of all the rotating and fooling around those not only rotating is not going to do a whole lot those pads are starting to wear on an angle so it's best to clean up your guides and pins make them work like you've got them if it's that big of a deal by cheap nice person pads for $9.99 off Amazon or locally from somewhere and slide them in there and then monitor how they do over the next few months for me it would take a few weeks I put a thousand miles a week on a car almost That's what I would do rotating the pads around like you're doing is going to start wearing the rotors funny and if you're worried about rotating pads out God's forbid what are you going to do about uneven wear on the rotors?

SM-A715F ?

 

If the rubber sleeves on the pins are swelling, that could be the reason for they're sticking. You can get replacement (part no 47875-12150) here, for one:

Rear disc brake caliper & dust cover for Toyota Prius XW30, 3 generation 01.2009 - 11.2011 - Toyota Car and Auto Spare Parts - Genuine Online Car Parts Catalogue - Amayama

Clean out all the old grease and start again with something that's non-swelling to rubber. Here in North America a readily available generic grease is:

AGS BK4 Sil-Glyde Silicone Brake Lubricant

The proprietary Toyota grease for this is:

Toyota recommended caliper pin lube:
Product Name: Toyota Rubber Grease
part number: 08887-01206
Content: Lithium Soap Base Glycol Grease (description on back of tube)

Also, the pics show "some" evidence, though not much, of misaligned piston: the "spoke pattern" (I mentioned up the page, and mispelled ) on the caliper piston face, must be oriented, and well seated thus, like a letter X. Otherwise the "spoke rides atop the pin on the pad backing plate, causing grossly uneven brake pad pressure, and this is evidenced by rusty zone on the disk.

Take a look at the last link in my signature.