Feedback in brake pedal (not warped rotors or ABS) - Subaru Outback - Subaru Outback Forums
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post #1 of 21 (permalink) Old 06-11-2019, 08:35 PM Thread Starter
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Feedback in brake pedal (not warped rotors or ABS)

I have a 2017 Outback with 37,000 miles. Every so often when I brake moderately hard I get an odd feedback through the brake pedal. It's similar to the feeling when the ABS is activating, but it's more pronounced and much much slower (Let's say for the sake of argument that ABS cycles 15x per second, this mystery feedback is maybe 2x per second). It's difficult to describe, almost like a pop in the pedal like it's ratcheting down as I apply the brakes. But again, this is only happening on a moderately hard braking event, for example stopping at a yellow light when going a bit too fast for the light timing. It might pop maybe 2-4 times as I stop. I can't figure out what causes it to happen, but it does always seem to be within the first few minutes of a trip.

I first noticed it at maybe 10k miles, but it was so infrequent that I never remembered to follow up on it. I took the car in a little while back for some other minor things, and the dealer blamed it on rotor runout. I explained that this was a completely separate issue from runout pulsing or warped rotors, but the service writer claimed that the rotors were so out of spec that it was tripping the ABS. I felt this so be BS, but I didn't pursue it, and the issue didn't repeat itself for a few thousand miles. However, it happened again today and it's becoming a concern since, you know, it's brakes. I've never felt that braking was impaired, but I have a concern that this might change at some point. This is the car that my family rides in.

If you're still with me thanks. I'll most likely bring it back to the dealer (where they'll tell me they can't reproduce the issue) but I'd like to hear if anyone else has experienced this before, or any other ideas on what to check.

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post #2 of 21 (permalink) Old 06-11-2019, 09:14 PM
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I wonder if it's the "Electronic Brake Distribution". It uses the ABS system to reduce braking force at the rear wheels to avoid rear wheel lockup during harder braking. EBD is on my 07 as well but I don't recall ever noticing it, including during those yellow light situations. (ABS itself kicks in when one or more wheels actually stops turning during hard braking to EBD is sort of a preventive precursor to ABS.)


Last edited by plain OM; 06-11-2019 at 09:19 PM. Reason: add
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post #3 of 21 (permalink) Old 06-11-2019, 10:22 PM
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could it be some issue with the check valve in the booster hose?

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post #4 of 21 (permalink) Old 06-12-2019, 04:50 AM
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I have also had this brake phenomenon on my 2017 Outback. Local Subaru dealership has inspected my brakes multiple times and have found no issues. Currently at just over 30k miles. Still feels a little uncomfortable to me. I was chalking it up to brake fade because I normally felt it in heavy traffic after lots of brake applications

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post #5 of 21 (permalink) Old 06-12-2019, 06:58 AM
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1 Lucky Texan's post reminded me of one braking "characteristic" I noticed in my 07 when it was new. This is not during a "panic" type stop; rather it more noticeable when coming to a "normal" stop with the pedal pressed moderately.

My 07 has the 4AT, which, of course, distinctly downshifts as the car slows. When it shifts from 2 to 1, but also sometimes 3 to 2, just when the shift takes place, there appears to be a small, short (time-wise) but perceptible change in the pedal back pressure (not so much a change in the actual pedal position) as if there's more braking assist being applied momentarily. The pedal otherwise remains firm. I long ago linked it to the effect of the downshift on intake manifold vacuum, and quickly stopped noticing unless intentionally watching for it.

I had discounted this for cars with the CVT, but then read a thread here about the "false shifts" that the later ones seem to have. If these CVTs also "downshift" in steps as the car slows, causing a distinct, rather than gradual, change in engine speed, it might be the same effect.
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post #6 of 21 (permalink) Old 06-12-2019, 09:24 AM
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I've been getting that from time to time. It has 54k miles on it now and nothing was ever found. Odd feeling but still brakes ok when needed so I've stopped being concerned over it.

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post #7 of 21 (permalink) Old 06-12-2019, 09:32 AM
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I believe @plain OM is basically correct, I'm pretty certain that's the EBD system pulsing the front brakes. So, perfectly normal. Mine does it too, and I referred to my owners manual for the answer . There it says the EBD system "maximizes the effectiveness of the brakes by allowing the rear brakes to supply a greater proportion of the braking force" depending on load and speed. Which is perhaps why most of us seem to wear out the rear pads much sooner than the fronts. I've noticed this feature is frequently activated near my office, when I'm coming to a stop sign at the bottom of a hill. It takes a good amount of pedal pressure to get the pulsing, so if you're really easy on your brakes, it may be a rare occurrence, if it happens at all. It's actually pretty infrequent for me, so I've often wondered if the EBD system is active more often that I realize - maybe it only occasionally needs to use the ABS system.
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post #8 of 21 (permalink) Old 06-12-2019, 09:46 AM
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is this a system that helps on snow or gravel? what is the reason for this?

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post #9 of 21 (permalink) Old 06-12-2019, 09:49 AM
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Happens almost exclusively on perfectly dry pavement, IME.
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post #10 of 21 (permalink) Old 06-12-2019, 12:20 PM
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Quote:
Originally Posted by plain OM View Post
I had discounted this for cars with the CVT, but then read a thread here about the "false shifts" that the later ones seem to have. If these CVTs also "downshift" in steps as the car slows, causing a distinct, rather than gradual, change in engine speed, it might be the same effect.
Simulated shifts (introduced at MY 2015) are programmed to occur only under moderate acceleration (~2700 rpm or higher) ... not under light acceleration or full-throttle acceleration. There are no simulated "downshifts."


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