[wilbur_xmas]

I don't know if this is of any help considering the wealth of track knowledge/experience already in here but I experienced something similar at my last track weekend at Thunderhill West.

I was in my V6 1LE with the factory Goodyear F1 Asymmetric 3 runflat street tires and had TC/ASC on as I am still a novice. It turned out I was leaning too much on the driver aids which overheated the rear brakes. The upgraded fluid was fine and didn't boil so the pedal was always firm but braking became unpredictable into the hard braking zones mid-session. Afterwards I discovered that the rotors were scored and pads worn which started creating some vibration under braking, but more importantly the rear started feeling loose under braking triggering ASC and creating a feedback loop requiring me to take a couple cool down laps or pit and return to get predictable braking back. The internal tire temps stayed consistent between 36-38 hot as per the performance supplement recommendations for my car, but perhaps the surface of the street tires was getting overheated causing the loose feeling. I didn't have a pyrometer so I can't verify tread temps, but the three main symptoms were: Loose feeling under braking, lack of overall braking force (despite firm pedal), slight vibration. At some points the ABS triggered early under moderate braking, which again makes me think the rear tires were overheated and greasy causing them to lock prematurely under braking while the fronts still had plenty to give, but this is just conjecture by an admitted novice. My plan for my next track day is to use actual track tires, reduce my pace, relax the nannies and slowly build my pace back up and cross my fingers that was the issue and that another set of rear rotors and pads are not in my immediate future again.

I don't know if you were watching to see how often you were triggering ASC warning light, but if you were seeing it often then you might need to relax the PTM settings as others have recommended.

[Swift016]

Originally Posted by wilbur_xmas

I don't know if this is of any help considering the wealth of track knowledge/experience already in here but I experienced something similar at my last track weekend at Thunderhill West.

I was in my V6 1LE with the factory Goodyear F1 Asymmetric 3 runflat street tires and had TC/ASC on as I am still a novice. It turned out I was leaning too much on the driver aids which overheated the rear brakes. The upgraded fluid was fine and didn't boil so the pedal was always firm but braking became unpredictable into the hard braking zones mid-session. Afterwards I discovered that the rotors were scored and pads worn which started creating some vibration under braking, but more importantly the rear started feeling loose under braking triggering ASC and creating a feedback loop requiring me to take a couple cool down laps or pit and return to get predictable braking back. The internal tire temps stayed consistent between 36-38 hot as per the performance supplement recommendations for my car, but perhaps the surface of the street tires was getting overheated causing the loose feeling. I didn't have a pyrometer so I can't verify tread temps, but the three main symptoms were: Loose feeling under braking, lack of overall braking force (despite firm pedal), slight vibration. At some points the ABS triggered early under moderate braking, which again makes me think the rear tires were overheated and greasy causing them to lock prematurely under braking while the fronts still had plenty to give, but this is just conjecture by an admitted novice. My plan for my next track day is to use actual track tires, reduce my pace, relax the nannies and slowly build my pace back up and cross my fingers that was the issue and that another set of rear rotors and pads are not in my immediate future again.

I don't know if you were watching to see how often you were triggering ASC warning light, but if you were seeing it often then you might need to relax the PTM settings as others have recommended.

Thanks, good info... I’m not sure why the nannies would overheat your rear brakes..., most braking is done by the fronts, so seems like they would give up first.. I have a decent understanding of ESC intervention, and I was using Competitive mode and Sport 2 track, so nannies should be minimized..

It’s possible there was air in front lines when I installed the Goodrich lines that was not bled..

Next I’m going to flush and service with Brembo HTC 64 and try again

Thanks,
Bill

[Zl1+911]

In my 911 (could not disable traction control ) I would experience rear brake fade without using them a lot and essentially it was the overactive traction system that uses rear brakes to control the car that was causing the issue. Intrusive traction control with advanced driving will definitely impact ur rear brakes

[wilbur_xmas]

Originally Posted by Swift016

I’m not sure why the nannies would overheat your rear brakes..., most braking is done by the fronts, so seems like they would give up first..

At least in my car the ESC calibration seems to primarily use/drag the rear brakes if there is any slip angle at all. I didn't realize at the time, but having since driven in competitive mode (no PTM on my car) which allows some slip angle, I now know I was heavily leaning on the ESC. The rear rotors/pads that were in great condition before the weekend were shot afterwards and even the dust seals on the caliper were melted while the front pads/rotors/seals were fine.

[juice3]

Originally Posted by Swift016

Guys,
I need help/feedback...
I have a 2019 XLE A10. ...only mods are Goodrich stainless brake lines and Motul 600 brake fluid.. Michelin Ps4s at 34psi hot.

Let's talk about this, bearing in mind I have a 815whp ZLE and track that hoe like a red headed step child.

I didn't like the Goodrich. I went to the CF Lines you can get on this forum.

Motul 600 cannot stand 4000# of this car and even a newbie driver. Get the SRF in there and don't look back.

PS4's - Ditch those ASAP get go to SC3R, get them on discount for 1200 easy.

You mention track alignment was "good", when was it good? What is your ToE settings?

The OE Toe Links are junk and you will have ToE issues the more you track.

Go to SPL and get everything You will thank me.

Any other questions hit me up.

[20Bluezl1]

Originally Posted by juice3

Let's talk about this, bearing in mind I have a 815whp ZLE and track that hoe like a red headed step child.

I didn't like the Goodrich. I went to the CF Lines you can get on this forum.

Motul 600 cannot stand 4000# of this car and even a newbie driver. Get the SRF in there and don't look back.

PS4's - Ditch those ASAP get go to SC3R, get them on discount for 1200 easy.

You mention track alignment was "good", when was it good? What is your ToE settings?

The OE Toe Links are junk and you will have ToE issues the more you track.

Go to SPL and get everything You will thank me.

Any other questions hit me up.

I tried ordering the CF lines and they have horrible customer service. They eventually returned my money because they didn't know when they could get a hold on the guys who ships them.

[juice3]

Originally Posted by 20Bluezl1

I tried ordering the CF lines and they have horrible customer service. They eventually returned my money because they didn't know when they could get a hold on the guys who ships them.

I can understand that. On my end I was just patient and I said I’ll get them when I get them. Because the other shit sucks.


Sent from my iPhone using Tapatalk

[Bangkok_ZL1]

Originally Posted by TrackClub

You must have been napping, or maybe having sex or something to drop 6 seconds solely due to tires
Not suggesting S4s are as fast as G3s, but sure as heck they are not 5 secs off on a buck 30 lap (assuming they are not completely cycled out).

Auto Club Speedway - Fontana, CA
1. 1:49.88 - birdmanf16 in '18 SS 1LE, OE Goodyear's, e85 tuned with CAI, Video
2. 1:50.60 - Tim202 in '18 ZL1 1LE, OE 3R tires, all stock see post #314
3. 1:51.91 - Destroyer_1LE in '17 SS 1LE on 5/20/18, PS4 Tires, Spoiler extension, see post #220
4. 1:57.066 - Rootsie in '18 V6 1LE on 10/7/18, Nexen NFERA tires see post #246
5. 2:00.18 - Rootsie in '18 V6 1LE on 5/4/19, P-Zero All seasons, stock

PS I recall we had this conversation before, but i cannot recall what exactly you fessed up to lol

PSS This is all in good humor, that's all. Cheers!

Having sex would be a good reason to be slower with the extra weight of the girl in the car and the drop in concentration....

[TrackClub]

Originally Posted by Bangkok_ZL1

Having sex would be a good reason to be slower with the extra weight of the girl in the car and the drop in concentration....

My logic exactly

[Swift016]

Originally Posted by TrackClub

My logic exactly

Wait, what ????...,, optional equipment ?? 😊

[TrackClub]

Originally Posted by Swift016

Wait, what ????...,, optional equipment ?? 😊

Not OEM, that's for sure

[AZ_1LE]

It's the tires. The car is meant to work with them and the 3R's level of grip. PS4S's are great street tires, but they are far from great on track, and you're feeling the brakes over-power them. Throw some 3R's or even some regular SC3's on the car and I guarantee you'll be happier.

[Swift016]

Originally Posted by AZ_1LE

It's the tires. The car is meant to work with them and the 3R's level of grip. PS4S's are great street tires, but they are far from great on track, and you're feeling the brakes over-power them. Throw some 3R's or even some regular SC3's on the car and I guarantee you'll be happier.

Thanks,
But I have 3r’s and the braking issue on track is the same with them...I understand the limitations of the Ps4s quite well.. This is a complex issue, and there is a cause... I just haven’t found it yet.. Believe me, I wish it was as simple as the tires..

I won’t bore you with the details hidden away in this lengthy number of texts..

Many thanks,
Bill

[TrackClub]

Originally Posted by Swift016

Thanks,
But I have 3r’s and the braking issue on track is the same with them...I understand the limitations of the Ps4s quite well.. This is a complex issue, and there is a cause... I just haven’t found it yet.. Believe me, I wish it was as simple as the tires..

I won’t bore you with the details hidden away in this lengthy number of texts..

Many thanks,
Bill

Have ya tried swapping the brake lines out for stockers yet?
Thinking about it a bit more, as much as it looks like F vs R brake bias, it could also be L vs R on the front causing the rear instability? Just a thought...Cheers!