Brakes intermittently engaging during turns at speed after replacing pads and rotors

drover135 · 08-28-2023, 06:33 AM

As the title states, changed my pads and rotors (Zimmerman blanks, EBC red pads), bed in procedure followed, and have since felt the brakes intermittently engaging on their own for maybe 1/2 second at a time at a mild to moderate intensity when I’m going through a turn at a decent speed. The harder I take the turn the more frequently I’ll feel it and the harder it will feel, but I’ve even felt it on a casual sweeping overpass. I’ve never felt it when I’m in a straight line. This happens with my foot completely off the brake pedal. When I do press the brake pedal, everything feels normal. Gas mileage is down 5 or 6 MPG as well.

Before I take everything apart again I thought I’d see if anyone has experienced this and knows of a solution. Thanks

jjFender · 08-28-2023, 07:21 AM

Sounds like the e-diff working.

But shouldn't have caused a massive fuel economy hit. Maybe the pads are dragging on the rotors and hurting your fuel economy and making the e-diff action more pronounced. Stopping after some straight highway cruising, do your wheels/brakes (front or rear) feel hot?

drover135 · 08-31-2023, 02:31 AM

Great idea regarding the E diff, you’re correct as I finally got a chance to go to my favorite twisty road tonight and tore through it with traction control on and felt the brakes bite a little here and there without me pressing the pedal, then turned DSC fully off and felt no brake engagement. Granted I was a little less confident with it off so I wasn’t going quite as fast but I ripped the last run and yeah, nothing.
I then got on the highway for a bit to cool off the brakes, pulled off and felt all the brake calipers and none of them felt warmer than the others. I then stupidly felt a rotor…ouch…but in the name of science I decided I had to feel the rest to see if that one was hot when it shouldn’t have been. No, they’re all just F’ing hot lol.
One of the calipers has to be engaged slightly though to decrease my gas mileage (I cleared it and drove around to confirm, I guess it’s more like 3 MPG less, not as bad as I thought but still significant), and I would guess when I’m pulling through a hard turn, if one of the wheels is being braked already maybe the E diff thinks that’s a problem and is then braking another wheel to counter it?
IDK, I’m just going to take them all apart again and see what I find

amg6975 · 08-31-2023, 08:30 AM

DSC will engage the front brakes quite a lot if you are sliding. With track pads up to temperature this can be pretty abrupt but should be barely noticeable with street pads. Turning off DSC does not turn off the ediff.

drover135 · 09-01-2023, 12:22 AM

Ah yes you’re correct, DSC not E diff. It’s just weird bc I’m not losing traction when this happens. And this is not during track use, this is just spirited city driving. I’ve replaced brakes many times on many cars, I guess I just put it back together with some minor flaw that I didn’t catch. Going to remove and reinstall next week, hopefully I’ll find the problem

tracer bullet · 09-01-2023, 07:45 AM

Any chance a brake line is routed wrong, and tugging a front caliper during a turn?

I think you said you tried changing settings and it made a difference, but now you're wondering about reassembling it wrong. If you get a front wheel off and start looking, maybe keep it in mind.

Maybe check the wheels for brake dust, if one is clearly heavier than the rest could be an indicator.

jjFender · 09-01-2023, 09:53 AM

E-diff is always on though. Turning off DSC should not turn off the e-diff. Honestly, I'm wondering if the brakes are dragging. You said you're an experienced brakes changer but was it the first time on a BMW? Maybe something was missed.

drover135 · 09-18-2023, 04:56 AM

Problem resolved (somehow). I finally got around to inspecting my brakes. Once I had the wheels off everything looked normal so I took the calipers off, inspected the rotors, pads, pistons, lines…I was disappointed to find that everything again looked normal so I thought I was going to have a more complicated issue to deal with. I just put it back together, but voila, the problem is now solved. Back to getting 30 mpg on the highway, no more brake grabbing in the turns…mysterious. Oh well.
Thanks for the input everyone

08-28-2023, 06:33 AM	#1
drover135 Enlisted Member 25 Rep 42 Posts Drives: 2012 135i 6MT Join Date: Dec 2022 Location: Austin, TX iTrader: (0) Garage List 2012 135i [0.00]	Brakes intermittently engaging during turns at speed after replacing pads and rotors As the title states, changed my pads and rotors (Zimmerman blanks, EBC red pads), bed in procedure followed, and have since felt the brakes intermittently engaging on their own for maybe 1/2 second at a time at a mild to moderate intensity when I’m going through a turn at a decent speed. The harder I take the turn the more frequently I’ll feel it and the harder it will feel, but I’ve even felt it on a casual sweeping overpass. I’ve never felt it when I’m in a straight line. This happens with my foot completely off the brake pedal. When I do press the brake pedal, everything feels normal. Gas mileage is down 5 or 6 MPG as well. Before I take everything apart again I thought I’d see if anyone has experienced this and knows of a solution. Thanks
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08-28-2023, 07:21 AM	#2
jjFender New Member 18 Rep 22 Posts Drives: BMW 135i Join Date: Jun 2023 Location: Canada iTrader: (0)	Sounds like the e-diff working. But shouldn't have caused a massive fuel economy hit. Maybe the pads are dragging on the rotors and hurting your fuel economy and making the e-diff action more pronounced. Stopping after some straight highway cruising, do your wheels/brakes (front or rear) feel hot?
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08-31-2023, 02:31 AM	#3
drover135 Enlisted Member 25 Rep 42 Posts Drives: 2012 135i 6MT Join Date: Dec 2022 Location: Austin, TX iTrader: (0) Garage List 2012 135i [0.00]	Great idea regarding the E diff, you’re correct as I finally got a chance to go to my favorite twisty road tonight and tore through it with traction control on and felt the brakes bite a little here and there without me pressing the pedal, then turned DSC fully off and felt no brake engagement. Granted I was a little less confident with it off so I wasn’t going quite as fast but I ripped the last run and yeah, nothing. I then got on the highway for a bit to cool off the brakes, pulled off and felt all the brake calipers and none of them felt warmer than the others. I then stupidly felt a rotor…ouch…but in the name of science I decided I had to feel the rest to see if that one was hot when it shouldn’t have been. No, they’re all just F’ing hot lol. One of the calipers has to be engaged slightly though to decrease my gas mileage (I cleared it and drove around to confirm, I guess it’s more like 3 MPG less, not as bad as I thought but still significant), and I would guess when I’m pulling through a hard turn, if one of the wheels is being braked already maybe the E diff thinks that’s a problem and is then braking another wheel to counter it? IDK, I’m just going to take them all apart again and see what I find
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08-31-2023, 08:30 AM	#4
amg6975 Captain 500 Rep 645 Posts Drives: '12 M1.5, '05 ZHP, '98 M3/4/5 Join Date: May 2017 Location: Rochester NY iTrader: (0)	DSC will engage the front brakes quite a lot if you are sliding. With track pads up to temperature this can be pretty abrupt but should be barely noticeable with street pads. Turning off DSC does not turn off the ediff.
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09-01-2023, 12:22 AM	#5
drover135 Enlisted Member 25 Rep 42 Posts Drives: 2012 135i 6MT Join Date: Dec 2022 Location: Austin, TX iTrader: (0) Garage List 2012 135i [0.00]	Ah yes you’re correct, DSC not E diff. It’s just weird bc I’m not losing traction when this happens. And this is not during track use, this is just spirited city driving. I’ve replaced brakes many times on many cars, I guess I just put it back together with some minor flaw that I didn’t catch. Going to remove and reinstall next week, hopefully I’ll find the problem
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09-01-2023, 07:45 AM	#6
tracer bullet Brigadier General 2418 Rep 3,550 Posts Drives: '11 135i , '15 X3 35i Join Date: May 2011 Location: Saint Paul, MN iTrader: (1)	Any chance a brake line is routed wrong, and tugging a front caliper during a turn? I think you said you tried changing settings and it made a difference, but now you're wondering about reassembling it wrong. If you get a front wheel off and start looking, maybe keep it in mind. Maybe check the wheels for brake dust, if one is clearly heavier than the rest could be an indicator.
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09-01-2023, 09:53 AM	#7
jjFender New Member 18 Rep 22 Posts Drives: BMW 135i Join Date: Jun 2023 Location: Canada iTrader: (0)	E-diff is always on though. Turning off DSC should not turn off the e-diff. Honestly, I'm wondering if the brakes are dragging. You said you're an experienced brakes changer but was it the first time on a BMW? Maybe something was missed.
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09-18-2023, 04:56 AM	#8
drover135 Enlisted Member 25 Rep 42 Posts Drives: 2012 135i 6MT Join Date: Dec 2022 Location: Austin, TX iTrader: (0) Garage List 2012 135i [0.00]	Problem resolved (somehow). I finally got around to inspecting my brakes. Once I had the wheels off everything looked normal so I took the calipers off, inspected the rotors, pads, pistons, lines…I was disappointed to find that everything again looked normal so I thought I was going to have a more complicated issue to deal with. I just put it back together, but voila, the problem is now solved. Back to getting 30 mpg on the highway, no more brake grabbing in the turns…mysterious. Oh well. Thanks for the input everyone
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