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I have followed the procedure to retract the piston I found on the forum using a disk type tool, it partially retracted the piston but needs to retract about 1/4 inch further. I have ordered the tool described in the procedure but worry about how much force to apply. Thoughts? Thanks much. The car is a 2015 Outback with electronic parking brake. ed
 

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I changed rear pads on 2017 legacy with the electric parking brake yesterday and it had the device shown attached to the back side of the caliper. if you look at the device you see the cap bolt ( silver color shown holding the rear electric part to the piston part. It is held on with 2 cap screws which can easily be removed with 5mm hex wrench. The 2 bolts holding the rear part on ( part with the 2 prong electrical connection) can probably be removed by 5mm hex wrench by hand. and i took the rear part off by twisting slightly while pulling it off, then the whole electric assembly comes loose and you get to the back side of the mechanical brake actuator.
It will expose what looks like a big torx or star bolt. Try to do this in a clean environment since there is some grease inside, and you don't want to introduce much dirt. I had a 12mm star or Torx type socket I put over the bolt and I really did not need to use the ratchet, but using the socket gave me enough extra leverage that i just twisted the socket to tighten and loosen it. You loosen it , or back it off the piston by twisting it CLOCKWISE , or opposite of normal way you would tighten something. I did this before removing the pads. and first twisted the shaft one way , and it only went probably less than 1/8 turn before it got tight and then twisted opposite direction all the way until it stopped. ( that retracts it all the way) It rotates several turns and will evidently bottoms out so you can push the caliper cylinder all the way back into the caliper so you can install new pads.
Then after installing the pads and putting the caliper back on I pushed on brake pedal a couple of times to get the caliper piston to tighten the pads, THEN I turned the shaft the opposite direction of loosening until it stopped. Since I did not want it tight against the pads. i backed it off full tight more than 1/8th turn before putting the back of the electric assembly and tightened the cap bolts again . i hope the eletric tightener adjusts itself once reinstalled, or else i got really lucky and rotated it the proper amount. but do not tighten it all the way snug before putting the electric assembly back on.

I am not a subaru mechanic. but i ran into a similar situation years ago working on our SAABs that We Rallied in the 80's & I did graduate as an engineer 50 years ago. . they had a mechanical device inside the calipers. that rotated to tighten over time as you applied the handbrake, and you had to buy a tool to rotate the caliper a lot to unscrew the mechanism inside the caliper. because the mechanical parking brake had to make a mechanical connection to lock the pads,not hydraulic. My assumption is this appears to be the way Subaru has done the same thing with an electrical tightener. it will slowly over time keep rotating like a screw to tighten the piston in as the pads wear out. and only have to rotate a little to tighten the pads, but as pads wear it keeps rotating to stay really close. it should also back off a little when you release the parking brake. (Does eyesight use this braking device? if so that may explain why rear pads wore out twice as fast as front pads). but rear brakes typically only supply less than a third of the braking on a vehicle.
I'm new to this and don't know how to attach pictures yet. once i figured out how it works, it is very easy to work with. and not really good at explaining. But if your rear brakes are like 2017 legacy/outback.
 

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The rears can wear fast because the car has the Electronic Brake Force Distribution.... that uses parts of the ABS system to increase rear brake pressure based on vehicle load and speed (prevents the front nose diving down). (Page 7-31 in the owners manual)

The motor there is only for the parking brake function.
 

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Remove the electric motor and retract the caliper from there.- 79mooneyman has it right very long winded.

 

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Just a note: you're not supposed to remove the EPB motor during pad replacement, and there's no need to, the full procedure has been posted in at least 2 other threads on this topic. The EPB also functions as your emergency brake, so it seems prudent to leave it undisturbed until the time comes for rotor replacement. There's also a specific service procedure involved when the EPB is removed to ensure it continues to operate reliably, which includes replacement of an o-ring.
 

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Just a note: you're not supposed to remove the EPB motor during pad replacement, and there's no need to, the full procedure has been posted in at least 2 other threads on this topic. The EPB also functions as your emergency brake, so it seems prudent to leave it undisturbed until the time comes for rotor replacement. There's also a specific service procedure involved when the EPB is removed to ensure it continues to operate reliably, which includes replacement of an o-ring.
The emergency brake function uses the VDC module. You can hear it under the hood when you use the emergency brake. It’s the same switch as the parking brake. The last bit is the EPB motor as you point out... (once the car has slowed enough).

Others have been able to do this job without removing the EPB motor in other threads. Wonder what's different here vs there?
 

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Just a note: you're not supposed to remove the EPB motor during pad replacement, and there's no need to, the full procedure has been posted in at least 2 other threads on this topic. The EPB also functions as your emergency brake, so it seems prudent to leave it undisturbed until the time comes for rotor replacement. There's also a specific service procedure involved when the EPB is removed to ensure it continues to operate reliably, which includes replacement of an o-ring.

Do you sell the special tool for retracting the piston??
 

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Just a note: you're not supposed to remove the EPB motor during pad replacement, and there's no need to, the full procedure has been posted in at least 2 other threads on this topic ... There's also a specific service procedure involved when the EPB is removed to ensure it continues to operate reliably, which includes replacement of an o-ring. [emphasis added]
Replacement of the O-ring is mandatory (per the Subaru FSM) whenever the EPB motor assembly is removed from the caliper. It is standard industry practice never to reuse an O-ring; they take a "set" in place and cannot be depended upon to seal properly when reused. The last thing you want is water (perhaps salty water) getting into the brake caliper and/or EPB gear train.

Besides, there is no need to remove the EPB motor assembly when retracting the caliper piston. The proper procedure is described fully in the Factory Service Manual.
 

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...The last bit is the EPB motor as you point out... (once the car has slowed enough)...
Pretty sure the E-brake description I've read said that, if all else fails (no hydraulic pressure), the motor will activate immediately.
 

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Pretty sure the E-brake description I've read said that, if all else fails (no hydraulic pressure), the motor will activate immediately.
yep - that too. Was in the same doc that ammcinnis posted in the other thread about the emergency brake operation.
 

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Just a note: you're not supposed to remove the EPB motor during pad replacement, and there's no need to, the full procedure has been posted in at least 2 other threads on this topic. The EPB also functions as your emergency brake, so it seems prudent to leave it undisturbed until the time comes for rotor replacement. There's also a specific service procedure involved when the EPB is removed to ensure it continues to operate reliably, which includes replacement of an o-ring.
Im new here and was wondering if you could post the links to the threads on this procedure since I am looking into doing the rear brakes on my 2016 outback premium myself for the first time and have never dealt with EPB before.
Thanks in advance.
Keith
 

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Brucey
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Im new here and was wondering if you could post the links to the threads on this procedure since I am looking into doing the rear brakes on my 2016 outback premium myself for the first time and have never dealt with EPB before.
Thanks in advance.
Keith
I have a video and write up here:


 

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Im new here and was wondering if you could post the links to the threads on this procedure since I am looking into doing the rear brakes on my 2016 outback premium myself for the first time and have never dealt with EPB before.
Thanks in advance.
Keith
Brucey has a good video of the procedure.

 

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I have a video and write up here:


Thank you for the quick reply. I’m going to check it out now.
 

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I have a video and write up here:


Did you leave the key in the “on” position after you disengaged the parking brake and while changing the brakes? Also I need to replace the rotors as well. Will they just come off easily after I take the caliper completely off or is there anything else I should Be aware of? Thanks
 

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Rotate the piston back as far as you can with the tool. When it stops rotating back, push the piston back the last 1/4" the old fashioned way. It slides back easily. I just did both my 2015 and 2018 this weekend. No need to remove other parts at all.
 

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Nope.

They should take off easily with the caliper bracket bolt.
Thanks again The reason I asked about the key in on position was because I wasn’t sure if for some reason the electronic parking brake engages when the car is in park and turned off.
 
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