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      08-10-2021, 09:03 AM   #23
NYG
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Quote:
Originally Posted by jfritz27 View Post
Is it analogous to what this guy is doing with ISTA to his E90?


(Buried within/part of a DSC recal routine?)

I don't (yet) have a copy of ISTA so can't confirm whether this function is present for our chassis
I think so. If I'm not mistaken I think the brake pressure sensors are called DSC pressure sensors on bimmers.
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      08-10-2021, 04:52 PM   #24
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Originally Posted by David0ff View Post
Quote:
Originally Posted by patrickd_21 View Post
Hi everyone,

Reaching out for help here as I'm at my wits end with the brakes on this car.

I bought myself a 2016 M3 with 5000 miles on pretty much 1 yr ago exactly. It's my daily and my lapping car at the moment.


When I bought the car, I slapped on some DTC-60 pads, Castrol SRF fluid, and off I went. The car was great all year and I got in 6 events.

The only complaint I had was that the pedal would get a tiny bit soft at the end of a 20min session. Probably due to the stock rubber lines expanding 17min into a hard session. Also, lots of wear on the outside of the tires


So over the winter I went out and bought stainless steel lines and camber plates. Had them installed by a shop, did a brake fluid flush, and was ready to start the year.


HERE is where the problems started.


At my first event, after a warm up lap, I started getting hard on the brakes and almost instantly, the brake pedal became very strange. The first 2-3 inches of pedal did nothing, and then all of my brakes were in the last 1-2 inches. I need to specify here that the pedal feel in the last 2 inches is good. Brakes are rock hard and I can brake HARD going into corners, it's just that since the pedal travel is so long and the brakes are all in the last few inches, modulation is difficult. I can do a full 20 min session going hard braking deep into braking zones, and it does not fade.

When I get off the track and the brakes cool, the pedal feels almost 90% better, but never perfect. I cannot replicate the low engagement point of the brakes in the street.

Here is the list of things I've tried that have had 0 impact on making it better:

- I thought there was maybe air in the system. Bled the system like 10 times. 2-3 times the traditional way. Once with a vaccum bleeder. 3 times with a power bleeder. Bled the ABS 3 times. Did a full fluid flush. I did it about 3 times. Another shop did it twice. Another shop did it 3 times. Another shop did it once

- I thought that since the issues started right after I did the brake lines, maybe it was the lines the issue. Swapped back to stock lines. Brakes still feel terrible, maybe even worse.

- Tried different pads (PFC-08). No difference


I'm getting real tired of this . 3 shops have bleed the brakes. I'm convinced there is no air in the system. I went back to my setup last year when everything was working well and that didn't fix things.

At this point I'm starting to get tired of throwing money at the issue and want to see if anyone has had this problem before. If no one has, my next step will probably be to rebuild the front calipers.

Please help lol
I use RBF660 motul with great success

Sometimes late in the 20 min session depending on how hard I push and how thin my pads are I do a "brake check" pedal tap before braking and it brings the pedal rock hard for the upcoming braking zone, try that and it will help you.
It's probably hard though because when you tap the brake like that you deplete the booster and also the orfices in the DSC unit are small so the fluid stay kinda pressurized. Could also be that you close up the running clearance caused by piston knock back.
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      08-11-2021, 12:09 PM   #25
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Quote:
Originally Posted by NYG View Post
If they went from blue to dark green that day then that means your caliper temps were without a doubt well beyond the boiling point of any fluid. It probably didn't feel like it because unlike other brake fluids, SRF will feel more or less normal once it cools down again and will require some work to reboil. That's why it's so amazing.

I also had green calipers and used PFC pads (08s run a bit hotter than any other pad I used).

I'm not sure how to do the reset on BMWs but if your brakes are only engaging at the end of travel then that would be the first thing I check (brake pressure sensors).
Many thanks! I was surprised how fast the brakes overheated - they were smoking after my first session (which I intentionally took easy). I guess a short track like Summit Point is not ideal for a heavy car like this, but still, one would have expected better brake heat management in a car this carefully engineered...

All best!
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      08-11-2021, 12:23 PM   #26
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Originally Posted by Mortis View Post
Many thanks! I was surprised how fast the brakes overheated - they were smoking after my first session (which I intentionally took easy). I guess a short track like Summit Point is not ideal for a heavy car like this, but still, one would have expected better brake heat management in a car this carefully engineered...

All best!
Anytime bro.

I dealt with miserable levels of brake heat on my F82 so I know your pain. I avoided a BBK for as long as possible until I realized that it was inevitable.
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      08-11-2021, 01:17 PM   #27
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Originally Posted by NYG View Post
Anytime bro.

I dealt with miserable levels of brake heat on my F82 so I know your pain. I avoided a BBK for as long as possible until I realized that it was inevitable.
Seems like that's the general consensus but the only thing that blows my mind is the Nurburgring taxis (specifically APEX) run many hours a day on stock calipers with different rotors and pads (on stock iron calipers not the CCB) and they have 0 issues.
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      08-11-2021, 01:43 PM   #28
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Quote:
Originally Posted by mitch32 View Post
Seems like that's the general consensus but the only thing that blows my mind is the Nurburgring taxis (specifically APEX) run many hours a day on stock calipers with different rotors and pads (on stock iron calipers not the CCB) and they have 0 issues.
Some guys here don't experience any brake heat issues but more than 3/4 of the F8x drivers I track with do.

I think it probably has a lot to do with all the speed and airflow on the ring even with lack of ducts. I would also assume that they're using street tires and not threshold braking with a full car of people. Aren't the taxis M5s? Or do they have others?
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      08-11-2021, 02:11 PM   #29
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Quote:
Originally Posted by mitch32 View Post
Seems like that's the general consensus but the only thing that blows my mind is the Nurburgring taxis (specifically APEX) run many hours a day on stock calipers with different rotors and pads (on stock iron calipers not the CCB) and they have 0 issues.
This....

My calipers went from blue to green last year and the pedal felt great

This year the calipers went from green to dark brown (running a stickier tire). Im a decent driver, I carry a lot of speed and brake hard on all corners, but I just don't see how APEX is running stock caliper with the caliber driver they have with no issue...
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      08-11-2021, 02:47 PM   #30
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Quote:
Originally Posted by patrickd_21 View Post
This....

My calipers went from blue to green last year and the pedal felt great

This year the calipers went from green to dark brown (running a stickier tire). Im a decent driver, I carry a lot of speed and brake hard on all corners, but I just don't see how APEX is running stock caliper with the caliber driver they have with no issue...
Well, to be fair they probably brake a lot less than us plebs.
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      08-11-2021, 02:49 PM   #31
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Quote:
Originally Posted by patrickd_21 View Post
This....

My calipers went from blue to green last year and the pedal felt great

This year the calipers went from green to dark brown (running a stickier tire). Im a decent driver, I carry a lot of speed and brake hard on all corners, but I just don't see how APEX is running stock caliper with the caliber driver they have with no issue...
Something is definitely up, the video at 6:00 the discuss the brakes as Pagid RSL29 with APP rotors which I think are girodiscs which maybe the aluminum hat helps dissipate heat fast.

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      08-11-2021, 06:51 PM   #32
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OP, this is unlikely solution to your problem given continued issues but I had a problem that gave me same symptoms. I discovered that when I swapped pads, my retainer spring wedged on one side inside the backing plate of a break pad and as such introduced space between disc and pad which allowed pistons to come out more on one side of one wheel. The brake pedal would engage lower and I couldnít do heel/toe but the brake force was still there once engaged. My gut feel is that one of the pins might have pushed the retainer spring a little when I first hit my breaks after swapping pads but canít say for sure. Hope this is helpful.
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      08-12-2021, 09:56 AM   #33
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Quote:
Originally Posted by dxj View Post
OP, this is unlikely solution to your problem given continued issues but I had a problem that gave me same symptoms. I discovered that when I swapped pads, my retainer spring wedged on one side inside the backing plate of a break pad and as such introduced space between disc and pad which allowed pistons to come out more on one side of one wheel. The brake pedal would engage lower and I couldnít do heel/toe but the brake force was still there once engaged. My gut feel is that one of the pins might have pushed the retainer spring a little when I first hit my breaks after swapping pads but canít say for sure. Hope this is helpful.
I suspected a spring at first, but after verifying everything many times, swapping many pads and I've eliminated the spring as a possibility. They are all well positioned.
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