OEM brakes toast after each track day

[strokemycocktus]

I have brake cooling ducts with Mumbray backplates, solid guide bushings on all four corners, new caliper seals, motul rbf 700 flushed around 2 months ago. I am running stock rubber brake lines since from what I read the SS ones are more of a placebo effect.
I use Ferodo DS 2500 for the rear and I used a set of DS 1.11 on the front in one day (35 laps).
I bought slightly used (about 16mm left out of 20mm) set of OE BMW performance pads (Pagid Rs 19?) which are also gone after one day (50 laps this time).

I run Pilot sport 4s. Discs are 1 year old.
I drove with MDM on on the first track day and turned it off for the second half of the other day. I had similar times and didn't crash so it probably didn't interfer that much.

The brake pedal is now very soft, it bites close to the floor, but the car brakes well overall. Even shortly after bleeding it had some dead zone at the top. On the track it was always soft and engaged rather low, but again, zero complaints about the braking performance.

I know my system needs bleeding now, but I feel like there might be something else wrong.
The caliper piston now is very hard to push back in, even though the seals are new. Doesn't matte if the bleeder is open or not. Also, pressure bleeder didn't work on any caliper, I had to pump the fluid the old fasion way.

Any ideas what might be wrong with my brakes and what should I inspect?

[Redd]

Not sure how it can brake well overall if its only biting close to the floor.

Sounds like you may have a damaged brake master cylinder or ABS/DSC pump.

[tdott]

sounds like air in the system, try bleeding it properly with the abs pump activation procedure.

INPA/ISTA or similar tool can do it.

[Kwike92M3]

Sounds like its time to go BBK! Essex and stoptech are running some promotions right now through various vendors!

[strokemycocktus]

Originally Posted by tdott

sounds like air in the system, try bleeding it properly with the abs pump activation procedure.

INPA/ISTA or similar tool can do it.

I was planning to do that. Can air in the system make the piston so hard to push in? I remember that last year I was able to do it by simply pulling the caliper with my hands, now I need to use a c-clip and a lot of force to squeeze it.

[strokemycocktus]

Originally Posted by Redd

Not sure how it can brake well overall if its only biting close to the floor.

Sounds like you may have a damaged brake master cylinder or ABS/DSC pump.

I know it sounds weird but that's how it works. I can brake really hard and engage ABS, but the pedal bites really low.

Now I am thinking about what could have caused the issues. Last year I went on a track day with stock pads and no cooling, I had fresh Castrol srf. I used 2 sets of OE pads in 1 day and melted one piston. After that I went to change the pads first, not knowing about the piston failure yet, and I forced the old fluid back to the brake lines (bleeder closed) maybe there was some dirt or air that I forced back up to the master cylinder? Could that cause such issues?

Photo of the piston attached. The calipers have been rebuilt of course (new seals, dust boots and pistons).

[slowdown_dan]

Originally Posted by Kwike92M3

Sounds like its time to go BBK! Essex and stoptech are running some promotions right now through various vendors!

That's not what it sounds like, at all. If he bolts up a new caliper and rotor and doesn't address the issues he's having ahead of the axle the same problems will occur. There is zero reason why the brake bits he's got on his system shouldn't perform well if everything else is functioning properly.

BBK is not life, and it does not solve all problems.

[tdott]

Originally Posted by strokemycocktus

I was planning to do that. Can air in the system make the piston so hard to push in? I remember that last year I was able to do it by simply pulling the caliper with my hands, now I need to use a c-clip and a lot of force to squeeze it.

yea it shouldn't be too hard to push in if things were working right, maybe the rebuild pistons were of lessor quality and not working right.

[Redd]

Originally Posted by strokemycocktus

I know it sounds weird but that's how it works. I can brake really hard and engage ABS, but the pedal bites really low.

Now I am thinking about what could have caused the issues. Last year I went on a track day with stock pads and no cooling, I had fresh Castrol srf. I used 2 sets of OE pads in 1 day and melted one piston. After that I went to change the pads first, not knowing about the piston failure yet, and I forced the old fluid back to the brake lines (bleeder closed) maybe there was some dirt or air that I forced back up to the master cylinder? Could that cause such issues?

Photo of the piston attached. The calipers have been rebuilt of course (new seals, dust boots and pistons).

I've destroyed my fair share of brake pads/discs at track but I've never seen pistons look like that. It looks like they heated up almost to melting point and the pressure from the pads deformed it. Question is, how did the pads survive if the pistons look like that.

[strokemycocktus]

Originally Posted by Redd

I've destroyed my fair share of brake pads/discs at track but I've never seen pistons look like that. It looks like they heated up almost to melting point and the pressure from the pads deformed it. Question is, how did the pads survive if the pistons look like that.

The pads were done almost to bare metal in no time. Yeah, that's what it looks like.

In the front calipers I replaced just the seals with ATE and reused the pistons since there were no OE ones available anywhere (I bought an extra used caliper with a good piston).

Yesterday I checked all the brakes and bled them with INPA. The pistons actually were quite easy to move back in, but only after the caliper was removed (if I tried to push them in like I usually did with a c clip pressing against the pad and the back side of the piston while mounted, it worked until a certain point but didn't move at all after that).
One other weird thing. I found that both upper rear caliper pins were gone, and the bottom ones were pretty loose already. I have no idea when they could have been lost and it scared me to see this. I didn't have any spares so I just bolted the bottom ones hard and left it like that.
After bleeding the brakes with the pump and replacing the front pads (they were completely gone) the brakes feel a bit better, still quite soft but they bite earlier. I assume it's because the rear calipers have a lot of flex being bolted up by only one pin - I'll check if it changes after I get the new parts.

Assuming the brake pedal feels ok again, what should I look at in terms of high temperature issues on track? Again, I have brake ducts so I thought the problem should be gone, but it isn't - I am attaching a photo of DS.11 pads from this season after 35 laps on a warm day. It's pretty crazy imo.

[Redd]

Have u considered the possibility that the pistons are warped and sticking inside the caliper cylinder? That's why they are hard to move. Does your brake pedal feel exceptionally stiff?

[strokemycocktus]

Originally Posted by Redd

Have u considered the possibility that the pistons are warped and sticking inside the caliper cylinder? That's why they are hard to move. Does your brake pedal feel exceptionally stiff?

Nope, as I wrote the pedal is soft and the pistons were easy to move back in once the caliper was taken off.

[strokemycocktus]

Also, I am very curious why doesn't the brake cooling help here. Maybe I screwed it up somehow?
I have corner splitters so I had to put the intakes closer to the center, then I routed an aluminium 45° pipe and attached 2" ducts that are attached to Mumbray plates. I thought it would make a massive difference in terms of heat.

[roastbeef]

Something is wrong for you to be burning through brakes that quick.

[strokemycocktus]

Originally Posted by roastbeef

Something is wrong for you to be burning through brakes that quick.

The track I go to is pretty heavy on the brakes that's for sure. F80 M3s are fine with DS2500 on the front with stock brakes though.
But what could be wrong? The only reason for these problems that comes to my mind is that something is interfering with the caliper making the pads still press against the rotor even after the pedal is released. But that seems rather unlikely since the car accelerates fine out of every corner, and after a full 20 min session I can easily push it around the paddock, all wheels spin freely.
I'll probably reinstall the missing pins for the rear, bleed the system with ABS pump once again, install RS19 pads for the front and I'll try another track day with MDM off for the whole day. If they are gone after that one day again I'll be out of ideas.

[strokemycocktus]

Also after my last track day last year all 4 rotors had some strange grooves on both sides. It's still there and I have no idea why it showed up.
The rotors are OEM BMW and were replaced a year ago, I've done 4 track days on them. The wear pattern is consistent for both sides of each rotor.

[bvrider1]

Subscribing... Hope you find out what it is.

[tsk94]

Good ducting like you've done/doing will certainly help. The next step would be to upgrade to a proper race pad. DS2500 are a dual duty pad and really not that good on track.

[strokemycocktus]

Originally Posted by tsk94

Good ducting like you've done/doing will certainly help. The next step would be to upgrade to a proper race pad. DS2500 are a dual duty pad and really not that good on track.

As I said I used DS 1.11 and OEM BMW Performance pads which are RS19 compound from what I read.
I use ds2500 just for the rear and they hold up quite ok (about 30% left after 2 track days).

[tsk94]

Originally Posted by strokemycocktus

As I said I used DS 1.11 and OEM BMW Performance pads which are RS19 compound from what I read.
I use ds2500 just for the rear and they hold up quite ok (about 30% left after 2 track days).

My mistake, thought it was DS2500 all around.

[roastbeef]

i run ds2500 on the street. i used them at the track when i first got my bbk. i've since moved up to a proper race pad, but i still use the ds2500 for the street. there was once when i used up my race pads and ran ds2500's on the track again and they did fine- not quite the bite i'd prefer and they wore quickly.

i've also used DSuno's, and ds1.11's, so i'm familiar with the compounds. i run stickier tires on a full bodied car (weight), and have a decent amount of seat time at laguna seca on the aforementioned pads. laguna is pretty brutal on brakes and i've never split a pad like that with that much meat on it. you're getting close to backing plate thickness, but its not so thin that you'll overwhelm the pad's heat capacity and disintegrate it. dsuno's and ds2500's tend to start chunking if you abuse them below the backing plate thickness, by the way.

maybe if your pistons aren't sticking, its the sliding assembly of the oem caliper that is not functioning properly. based on what you're describing, it sounds like a stuck piston, but that would be pretty obvious. also, drive around normally, then take off a wheel and try to rotate the disc by hand. there is going to be some resistance on a brake assembly that is in good working condition, but if you have something sticking, it is going to be much harder than usual to turn.

this is an obvious heat problem, but you're on street tires with good ducting. i'm not sure what else would cause this other than excessive heat from some kind of sticking.

[strokemycocktus]

Originally Posted by roastbeef

i run ds2500 on the street. i used them at the track when i first got my bbk. i've since moved up to a proper race pad, but i still use the ds2500 for the street. there was once when i used up my race pads and ran ds2500's on the track again and they did fine- not quite the bite i'd prefer and they wore quickly.

i've also used DSuno's, and ds1.11's, so i'm familiar with the compounds. i run stickier tires on a full bodied car (weight), and have a decent amount of seat time at laguna seca on the aforementioned pads. laguna is pretty brutal on brakes and i've never split a pad like that with that much meat on it. you're getting close to backing plate thickness, but its not so thin that you'll overwhelm the pad's heat capacity and disintegrate it. dsuno's and ds2500's tend to start chunking if you abuse them below the backing plate thickness, by the way.

maybe if your pistons aren't sticking, its the sliding assembly of the oem caliper that is not functioning properly. based on what you're describing, it sounds like a stuck piston, but that would be pretty obvious. also, drive around normally, then take off a wheel and try to rotate the disc by hand. there is going to be some resistance on a brake assembly that is in good working condition, but if you have something sticking, it is going to be much harder than usual to turn.

this is an obvious heat problem, but you're on street tires with good ducting. i'm not sure what else would cause this other than excessive heat from some kind of sticking.

That got me thinking and I remembered that when I was installing the brass bushings I had to make the bores wider since the pins didn't fit and move freely. I used a 12mm drill and smoothed it out with fine sandpaper. They fit and move freely, but what maybe the tolerance is just a bit too tight and when it all gets very hot the pins and bushings sell and the sliders stick.
I could buy a 12.1mm or even 12.2mm drill and make the bores just so little bigger to make the fit by 0.1 mm looser. This shouldn't introduce any play and should allow free movement in all extreme conditions.
What do you think?