Back Yard Brake Pad Replacement for 2015 Gen III Prius

Pad life looks good.

 

As an interesting aside, I noticed one of my rear rims was too hot to touch after driving 15 miles, and the other rear was just slightly warmer than the fronts. I broke into it today and found both sets of rear pads dragging roughly the same amount, caused by severe corrosion of the pad ears that nest in the stainless pad support plates. Basically they were immovable, and the piston was putting constant pressure on them--I backed the pistons off 1/4 turn to relieve the pressure. By filing off the rust and dosing with antisieze I got them back into serviceable condition. Driving a short distance and raising the rear confirms they no longer drag, for now at least.

Does anyone know what the arm sticking out at 90 degrees from the inner pad does? I actually couldn't reinsert the inner pads before I realized that the arm was catching on the support plate and needed lubrication. Maybe it's causing some stiction? It also seemed like the height of the slot had decreased a little, either by corrosion and expansion of the pad ears, or the caliper surface underneath the stainless support plate.

I still cannot believe how bad the rear brakes fair on this car. By comparison, the fronts are wearing uniformly, not siezed, and still have traces of antisieze on the ears. All are 3 years--20k miles--old. I notice that the upper front pad ears have a stainless hump-shaped bearing surface that reduces friction (I guess) and doesn't rust. None of the aftermarket options for rear pads feature this. Is it possible to get rear pads that resist corrosion? I bought very cheap pads, and perhaps I got what I paid for, though they are doing miraculously well on the front of the car. I need to start lubing these twice a year if I want to try and crawl back to 60 mpg.

Also, it does say in the maintenance book to inspect the brakes every 5k, which I mostly have ignored, to my peril. The prius does live up to its reputation for great pad longevity, unless you fail to do preventive maintenance and live in the rust belt--in which case it's probably worse than a regular car.

 

Besides the "visual" inspection every 5K (which is essentially the tire rotation guy eyeballing them as he goes), Toyota USA recommends the a full inspection every 30K or 3 years. Check the guide; it's kinda subtle.

Did you confirm the piston face spoke pattern orientation was like an X, and the the piston was well seated against the inside pad thus? Not doing that WILL cause steady drag, and bevelled pad wear, and the inside face of rotor will be 50% rusty, due to lack of contact with the pad. Here's a screen grab from the attachment I posted earlier in this thread. You need to ensure things go together thus, and stay seated thus:



Here's how rear brakes in good order should spin:

 

Thin little spring steel arm, riveted onto the pad, curves around, points toward the rotor?

The end that points toward the rotor will touch the rotor surface and make a horrible screech when the lining has worn past the minimum.

I could believe that's happening to mine a little. I took the support plates ("fitting kit") out and used a file lightly once on the channel underneath them.

What condition were your support plates in? The fitting kit is cheap (includes those plates and the little V springs for the pad tops) and the plates, when new, have a Teflon-like dry coating. They're not made to be greased (would just collect dirt), but the factory coating is pretty slick. When it's all right, you need one hand to squeeze the pads together while you flip the caliper back down, or the V springs will slide them right apart.

I check mine about every tire rotation, and any rust on the ears pretty much rubs off, which I do, and that seems to keep them decent. But they're OEM pads ('cause my 2010 isn't old enough to have needed new ones yet).

Couldn't have said it better.

One simple, no-disassembly preventive check you can do about any time is the old stone-cold after test-drive test. (The only trick is to plot out a test drive you can complete without using the brakes, or they'll be a bit warm unavoidably.) That will easily alert you if there's a brake that needs a closer look.

 

Also serves as a little handle, as you're trying to fish the inside pad in there.

 

That's a great video. Mine do spin like that now.

I am sure the piston is oriented thus because I put it on correctly last time and only rotated 1/4 turn. The illustration itself is not helpful because it's not obvious if it is light or dark recessed. Memory serves that the recess should be at 12 o clock because that's where the pin is.

I had all of the symptoms you describe (uneven wear, 50% rusty inner disc, etc) but caused by corroded pad ears. Unless there's something wrong with the caliper--it's odd that the piston was putting so much pressure on the pads. I will double check it tomorrow.

 

Oh, a squealer, and a little handle.

They're a little scratched up. Underneath it wasn't bad looking; I just scraped it with a screwdriver. Considering the parts move so little, is attracted dust really a problem? Maybe some of my seisure causing material was clay or brake dust plus dried up antisieze. However, I treat the front pads exactly the same, and they were very clean and properly functioning, albeit with the advantage of having superior bearing surfaces (domed stainless tab, and the bottom ear is channeled through the middle).
It's definitely not slippery as you describe, but I got them moving pretty well.

Great test!

 

That's correct.

Yeah, the shaded areas are the high bits, and you want the pin between them. I think too, you could get the orientation right, then if you immediately stomp the parking brake pedal, it'll try to rotate the piston, or "cam" it out slightly, to lock the brake. You want the latter to happen, but not the former. So tromping the brakes, and forestalling use of the parking brake till the brakes are well seated, after a test drive, helps prevent that.

 

There are great videos showing this.

 

Yeah I would have just cleaned and reinstalled those. Good you got it done.

Did you double-check the rears? After you've test driven, then applied/released the parking brake a few times: raise the rear (front wheels chocked, parking brake released) and see that the wheels spin semi-freely. There's some drag inherent in a disc brake, but they should spin 2~3 revolutions with a push.

 

Good job, yeah those old pads look thick!

How were the slide pins? rears in mine and a few others in the "Salt" belt were rusty in a bad way.
I actually had to replace mine for safety (peace of mind) sake, although when first found I lubed them good
and went a week before receiving new in the mail.

 

The transaxle is a CVT in the sense there are no selectable gear ratios. It is simply an electric motor. The oil only serves to keep the temperature regulated and the parts lubricated.