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      08-21-2018, 06:25 AM   #1
SapphireM5
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Hey guys quick question, hoping someone can test this for me. I did my brake fluid flush as I was due for the service and I think I am being hypersensitive to brake pedal feel. The brake pedal feels perfect and stops on a dime while driving, nice and firm. If I stop in my driveway and hold the pedal, lift off the pedal and re apply light pressure on the brake pedal it feels a lot lighter. The pedal drops about 1/2" -1" when I re apply it very lightly. If the car moves 1' forward before I reapply the brake pedal is nice and firm again. I have a feeling it's the drive-off assist I am feeling as the rear calipers are slightly engaged until the car moves a little. Can someone just check there's for me to see if yours does the same thing please. I have bled the brakes several times w the power bleeder to make sure there's is no air. Thanks in advance guys!
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      08-21-2018, 11:47 AM   #2
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Not tried mine but sounds normal to me. You'll probably get the exact same feeling if you press the pedal with handbrake applied then release the handbrake while keeping your foot on the brake. As the pistons in the rear calipers return, the fluid is pushed back into the master cylinder therefore pushing your pedal up.

Your thought of the brake holding the car sounds right to me. Sometimes the hydraulics will be held at the pressure the user last requested until the driver touches the throttle. Could be different on the M5 though.

Last edited by Dwaynos; 08-21-2018 at 12:20 PM..
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      08-22-2018, 05:10 PM   #3
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Quote:
Originally Posted by Dwaynos View Post
Not tried mine but sounds normal to me. You'll probably get the exact same feeling if you press the pedal with handbrake applied then release the handbrake while keeping your foot on the brake. As the pistons in the rear calipers return, the fluid is pushed back into the master cylinder therefore pushing your pedal up.

Your thought of the brake holding the car sounds right to me. Sometimes the hydraulics will be held at the pressure the user last requested until the driver touches the throttle. Could be different on the M5 though.
Ah, thank you very much for replying! Anyone else willing to check there's for me?
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      08-23-2018, 10:23 AM   #4
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Quote:
Originally Posted by SapphireM5 View Post
Hey guys quick question, hoping someone can test this for me. I did my brake fluid flush as I was due for the service and I think I am being hypersensitive to brake pedal feel. The brake pedal feels perfect and stops on a dime while driving, nice and firm. If I stop in my driveway and hold the pedal, lift off the pedal and re apply light pressure on the brake pedal it feels a lot lighter. The pedal drops about 1/2" -1" when I re apply it very lightly. If the car moves 1' forward before I reapply the brake pedal is nice and firm again. I have a feeling it's the drive-off assist I am feeling as the rear calipers are slightly engaged until the car moves a little. Can someone just check there's for me to see if yours does the same thing please. I have bled the brakes several times w the power bleeder to make sure there's is no air. Thanks in advance guys!
I think what you might be describing is a result of the vacuum assist. This could be the case if it only occurs whilst the car is stationary, or off, because under driving use the vacuum is fully generated all the time. If the brakes are fine when driving, then I can’t see a problem.

Mine are due a fluid change. They feel soft, especially at the top of the pedal stroke, braking hard.. I’ll also replace the rubber hoses for braided for maximum improvement.
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      08-23-2018, 10:33 AM   #5
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Quote:
Originally Posted by DTP1980 View Post
Quote:
Originally Posted by SapphireM5 View Post
Hey guys quick question, hoping someone can test this for me. I did my brake fluid flush as I was due for the service and I think I am being hypersensitive to brake pedal feel. The brake pedal feels perfect and stops on a dime while driving, nice and firm. If I stop in my driveway and hold the pedal, lift off the pedal and re apply light pressure on the brake pedal it feels a lot lighter. The pedal drops about 1/2" -1" when I re apply it very lightly. If the car moves 1' forward before I reapply the brake pedal is nice and firm again. I have a feeling it's the drive-off assist I am feeling as the rear calipers are slightly engaged until the car moves a little. Can someone just check there's for me to see if yours does the same thing please. I have bled the brakes several times w the power bleeder to make sure there's is no air. Thanks in advance guys!
I think what you might be describing is a result of the vacuum assist. This could be the case if it only occurs whilst the car is stationary, or off, because under driving use the vacuum is fully generated all the time. If the brakes are fine when driving, then I can’t see a problem.

Mine are due a fluid change. They feel soft, especially at the top of the pedal stroke, braking hard.. I’ll also replace the rubber hoses for braided for maximum improvement.
Thanks bud! Vacuum should be the same at idle so that should be good. My car only has 8k miles I changed it due to time. I'm thinking I'm feeling the drive off assist since while that's activated those pistons are pushing out so the fluid has yet to return causing that pedal feel for a second. Car stops on a dime, I feel like the braking has improved tremendously after the fluid change even though they were awesome before. Can you feel what I'm describing in your pedal? Thanks
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      08-23-2018, 03:31 PM   #6
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It's not a vacuum issue, as you said, the system will still be very effective at idle, the pedal will actually get harder if you pump it rapidly as it purges the servo.

Checked mine for you, as I mentioned in a previous post, I'm sure the auto hold maintaines the previous pressure and therefore holds the car still, if you touch the pedal again afterwards you have some free play before the pedal comes to a solid stop. If you move forwards or backwards then press the pedal again it feels normal. At that point the car had released the pressure and the pistons returned to their released positions.

I'm not sure how much you are pressing the pedal when you say it feels a lot lighter, maybe you are referring to the extra free play in the pedal. Try pressing it further and see if it goes solid like I mentioned.

Hope this helps.
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      08-23-2018, 03:41 PM   #7
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Quote:
Originally Posted by Dwaynos View Post
It's not a vacuum issue, as you said, the system will still be very effective at idle, the pedal will actually get harder if you pump it rapidly as it purges the servo.

Checked mine for you, as I mentioned in a previous post, I'm sure the auto hold maintaines the previous pressure and therefore holds the car still, if you touch the pedal again afterwards you have some free play before the pedal comes to a solid stop. If you move forwards or backwards then press the pedal again it feels normal. At that point the car had released the pressure and the pistons returned to their released positions.

I'm not sure how much you are pressing the pedal when you say it feels a lot lighter, maybe you are referring to the extra free play in the pedal. Try pressing it further and see if it goes solid like I mentioned.

Hope this helps.
Thanks so much for the help buddy! What I mean by light or free pedal is when I go to re apply the pedal while still stopped, the first 1/2" or so of pedal travel feels light then the pedal is firm from there on. That 1/2" of light pedal I believe is the pistons in the rear still pressing against the rotors on the "hold". Just wanted to confirm other members are feeling the same, so I can stop being so neurotic about it. But I must say the past year and a half I have owned the car I thought the brakes were awesome. Now they are awesome plus on steroids lol. Maybe it's just me but I feel like after the flush they are so much better. And my fluid was flushed two years ago by BMW. Thanks again for all of your help!!
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      08-23-2018, 04:13 PM   #8
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Yes that free play you experience is caused by the extra "space" inside the hydraulics when the pistons are held out.

Did you change to upgrade fluid or just a simple replacement? I need to do mine really but in two minds about changing to upgraded fluid.
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      08-23-2018, 04:15 PM   #9
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Quote:
Originally Posted by Dwaynos View Post
Yes that free play you experience is caused by the extra "space" inside the hydraulics when the pistons are held out.

Did you change to upgrade fluid or just a simple replacement? I need to do mine really but in two minds about changing to upgraded fluid.
Thanks so much!!!! Yes, I flushed the brake fluid because it was due for service. I used factory BMW brake fluid. I used a motive power bleeder which made the job cake.
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      08-23-2018, 04:36 PM   #10
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Auto hold isn't on unless you turn it on. See auto H. button on console.
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      08-23-2018, 04:39 PM   #11
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Auto hold isn't on unless you turn it on. See auto H. button on console.
Auto hold I believe is on the newer cars, our cars it's called "Drive off assist." I holds the rear brake calipers closed for a few seconds during transition from brake pedal to accelerator.
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      08-23-2018, 07:32 PM   #12
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There is no appreciable difference in pedal feel to me (very slightly spongy at the top and increasing firmness with increased pedal pressure) when braking with the drive off assistant engaged or after the drive off assistant has been engaged. At no time does my pedal go light. The only thing that creates a different pedal feel to me is pumping the brake pedal in which case the sponginess is gone from the top and it will be firm from the get go.
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      08-23-2018, 07:37 PM   #13
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Quote:
Originally Posted by DL7 View Post
There is no appreciable difference in pedal feel to me (very slightly spongy at the top and increasing firmness with increased pedal pressure) when braking with the drive off assistant engaged or after the drive off assistant has been engaged. At no time does my pedal go light. The only thing that creates a different pedal feel to me is pumping the brake pedal in which case the sponginess is gone from the top and it will be firm from the get go.
Thank for checking, that is basically what I am describing. Maybe "light" was the wrong word, but the very top of the pedal throw with the drive assist active feels different, then firms up past that point. While driving pedal is always firm.
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      08-23-2018, 07:48 PM   #14
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Mine actually has identical pedal feel when braking during driving as well. The identical very slight sponginess at the top is also present. My fluid is due to be replaced soon so I don't know if that will make a difference.
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      08-23-2018, 07:56 PM   #15
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Quote:
Originally Posted by DL7 View Post
Mine actually has identical pedal feel when braking during driving as well. The identical very slight sponginess at the top is also present. My fluid is due to be replaced soon so I don't know if that will make a difference.
You may feel a nice difference when you change the fluid. Just make sure if you do it or have someone do it that they use a power bleeder. My local BMW charges 90 for brake fluid flush. GL and really, thank you for the reply!
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      08-23-2018, 08:13 PM   #16
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Btw, the only time I believe my brake pedal is firm from the start while driving is under sudden braking. I believe we have a brake assist feature that increases brake pressure under sudden braking. Perhaps that is why you feel a firm pedal when braking while driving.

My car is still under a maintenance plan so my brake fluid will be done at the dealer.
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      08-23-2018, 08:17 PM   #17
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Quote:
Originally Posted by DL7 View Post
Btw, the only time I believe my brake pedal is firm from the start while driving is under sudden braking. I believe we have a brake assist feature that increases brake pressure under sudden braking. Perhaps that is why you feel a firm pedal when braking while driving.

My car is still under a maintenance plan so my brake fluid will be done at the dealer.
Makes Sense, thanks!
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      09-10-2018, 11:27 AM   #18
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Quote:
Originally Posted by SapphireM5 View Post
Auto hold I believe is on the newer cars, our cars it's called "Drive off assist." I holds the rear brake calipers closed for a few seconds during transition from brake pedal to accelerator.
That's correct for the '13 and it may confuse a new owner on a hill waiting not knowing it will roll back after a few seconds after taking foot off the brake.
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