So, I've had this problem for years where you could hear a sort of metal on metal rubbing sound coming from the rear wheels in EV mode (because it's quiet). Recently, while in for yearly inspection the shop said all the rotors, pads and tierods needed replacement and since I now have a house and garage, I thought I would do it myself, learn some things and save some money.

The shop also mentioned that something was weird about the rear brakes on the vehicle but they didn't troubleshoot the exact problem. While I had it apart, today, I noticed that the outer pad was almost worn completely and the inner pad had what looked like to me, almost no wear. Either way, I installed the new rotor and pads (I've only done one side so far) and got the wife to cycle the brakes while I watched. I noticed that the caliper never seemed to retract or whatever so the outer pad was still in intimate contact with the rotor causing quite a bit of drag on the wheel.

Does anyone know what is wrong here? Is there something wrong here?

BTW, turns out the FEH inner tierods require a goofy size tool that none of the local stores have so if anyone else has to do this, I recommend purchasing the Lisle 'MASTER Inner tie rod' tool kit.

 

I would check your parking brake shoes as well. I have had those drag on other vehicles when they were too worn (due to uneven wear from some crackhead previous owner driving around with the brake still on). Often it will create the sounds you are describing without a huge impact on acceleration/performance.

Also check the wheel bearings. A failing--but not yet failed--bearing can produce a scraping or dragging sound very similar to brakes.

Lastly, I have always had the pads sitting against the rotor after reinstallation. This is to be expected as you rarely can get that caliper to fully retract by hand. When that rotor gets to spinning good the first time you drive it after installing new pads, it will kick the pads back-- don't worry. The gap between pads and rotors is minuscule under normal circumstances-- otherwise you would get a ton of travel in the brake pedal.

Check the parking brake shoes and the wheel bearings. Given how rear brakes aren't used that much on this vehicle and how long it takes to wear out the fronts due to regenerative braking, I would expect abnormal pad wear on all the wheels (and that is what I observed when I changed mine).

Also, be sure to break in your new pads. Take your car up to ~60, shift it into neutral to disable regenerative braking and brake hard (without triggering anti-lock) down to about 10-15 mph. Do this over and over until you can smell those pads cooking. This will ensure you don't get any vibrations or "warped rotors"-- a little tip I learned a few years ago after many years of changing perfectly good rotors, lol.

 

Sounds like you have a seized piston, so get a reman caliper & put it on. I made an entry on caliper replacement and how to avoid the special bleed procedure by capping the brake line quickly when you take the hose off. Also replace the flex hose when you do the caliper.

 

Supporting what Bill said, calipers do seize and have to be replaced. The low break wear on FEH's means this is more likely to show up before other components are worn out. If they are left, it leads to premature pad and disc wear. I assume you have a pre'09? What mileage does it have on it?

 

I'm not sure you can really see the caliper retract by just observing it visually, unless you really know what you are looking for. The travel is really small with new pads installed...

 

Plus, a seized caliper piston would really cause a lot more symptoms than a noise-- you'd get a lot of heat, odor, scoring of the rotor itself, tons of brake dust, etc. I've seen a couple on much older vehicles and it was REALLY obvious that the brakes were dragging...

 

Oh, sorry, I should have said before. It's a 2006 FEH FWD with roughly 75k.

I don't think it is the parking brake or wheel bearings since with the caliper removed the wheel spun nicely. In fact, with the old unevenly worn pads it spun freely until I had the wife hit the brakes to make sure the caliper was working at all. One of the 'guide?' pins felt a little weird when I was both removing it and when I reinstalled it. It felt like it was cross threaded or possibly installed at an angle. I wonder if that could prevent the caliper assembly from centering and/or moving correctly. One of the pins also looked scratched or something which seemed odd. Finally, I didn't have any problems compressing the caliper to remove it or to install the new pads so I don't think the caliper piston is seized.

When I say the pads were uneven, I really mean that the inner pad looked almost new and the outer pad was shot. They really were totally uneven. When I did the front pads and rotors last weekend, the wear was much more even and as I would expect.

Even though it is really cold and dark out now, I really want to take apart the other side to see how things compare.

 

My stock rear pads were very similar to what you are describing when I replaced them at ~100k. Much more uneven wear than the fronts.

As far as those caliper bolts, my wife's old Mazda 6 had a bolt that would always lose torque when I reinstalled it (she went through brake pads like crazy). I just kept reusing it until I noticed a clunk when braking and scraping during initial acceleration. That's when I realized that bolt had popped out somewhere on the road and the caliper was rotating forward and smacking the inside of the wheel, lol! So, I got some new bolts at that point.

I'd suggest finishing the brake job, replacing those questionable caliper guide bolts as you do it, break the new pads in and then see if the problem is still there.

I'm still betting on a wheel bearing

 

I still need to order the correct inner tie rod tool end piece for the replacement inner tie rods ( they're different from stock ones) so the guide pin bolts were on my list of parts to possibly get and replace as well.

I remember hearing or reading elsewhere that you shouldn't 'heat up' new pads to seat them or break them in or whatever it is you're supposed to do. Unfortunately, I can't remember the reasoning behind this.

Another reason why I don't think it is the wheel bearing is that it has done this almost since I bought it. I even asked a dealer mechanic to 'look' at it when I had it in for some service years ago. They claimed they didn't notice anything 'wrong'.

 

I bought the Powerstop pad/rotor set for my FEH and the break-in procedure was delineated and required for proper support.

You got to bed them in to the rotors or they won't mate correctly. Just keep it out of ABS and don't come to a complete stop during any point of the process and you'll be ok. Let the brakes cool before setting the parking brake.

http://www.zeckhausen.com/bedding_in_brakes.htm