Brake pedal travel issue - F80 M3 - Steel Brakes

[NYG]

Originally Posted by jfritz27

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.

[mitch32]

Originally Posted by David0ff

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.

[Mortis]

Originally Posted by NYG

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!

[NYG]

Originally Posted by Mortis

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.

[mitch32]

Originally Posted by NYG

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.

[NYG]

Originally Posted by mitch32

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?

[patrickd_21]

Originally Posted by mitch32

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...

[NYG]

Originally Posted by patrickd_21

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.

[mitch32]

Originally Posted by patrickd_21

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.

[dxj]

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 couldn’t 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 can’t say for sure. Hope this is helpful.

[patrickd_21]

Originally Posted by dxj

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 couldn’t 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 can’t 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.

[sly1types]

I think like others have said these calipers just arn't great, especially with knock back. I went to giro disc and PFC11 and i have good brakes, but not amazing. I have to tap them before the brake zone on 2 hard brake zones. I also have cooling ducts coming off the splitter and they don't fade, but i just don't like the pedal feel.

I run Motul 600, stainless lines also. After these rotors are done i will probably go with the StopTech ST60 kit. I have the ST40 on my E46M for the last 10+years and they are just always solid.

How many people run knock back springs? Do the always drag on the rotor even on the street?

[melanthius]

I need to do this too... I have felt like my brakes have needlessly long travel for as long as I've had the car

[D_SheerDrivingPleasure]

Originally Posted by melanthius

I need to do this too... I have felt like my brakes have needlessly long travel for as long as I've had the car

I plan to squeeze all the juice out of the OEM calipers before going BBK.

stage 1 - remove dust shield ($0)

stage 2 - install a two piece rotor ($2400 for both axles)

stage 3 - install stainless steel pistons, high temp seals and dust boots ($600 for both axles)

stage 4 - remove any air from system

Can we call this a small brake kit?

[melanthius]

Originally Posted by D_SheerDrivingPleasure

I plan to squeeze all the juice out of the OEM calipers before going BBK.

stage 1 - remove dust shield ($0)

stage 2 - install a two piece rotor ($2400 for both axles)

stage 3 - install stainless steel pistons, high temp seals and dust boots ($600 for both axles)

stage 4 - remove any air from system

Can we call this a small brake kit?

I've been thinking along similar lines.

I've done the stainless pistons, high temp seals, dust boots, and titanium shims. Stainless lines and fluid of course. Getting air out is totally mandatory.



I feel this will get me some more life out of OEM system at the track before blowing my budget on BBK.

Not sure why but on this car almost nothing I do makes the brakes feel amazing. When I used to have my 350Z back in the day, after similar brake upgrades I had a rock solid pedal and amazing feel. Maybe its this calibration thing. No idea.

[bimmerboyE92]

Not sure that $3k in upgrades makes sense when the front BBK is $5k and has demonstrated resale upwards of $3k on the used market. Sounds like you would be money ahead just upgrading now. Just a thought.

[D_SheerDrivingPleasure]

Originally Posted by bimmerboyE92

Not sure that $3k in upgrades makes sense when the front BBK is $5k and has demonstrated resale upwards of $3k on the used market. Sounds like you would be money ahead just upgrading now. Just a thought.

My poor man's brake kit costs 3k vs 10k for an AP setup on both axles. For me, it's all or none.

Also,

- my f80 is a dual duty car and I'm not sure I could tolerate the pad rattle of a BBK on a daily basis, especially on lousy NYC roads.

- my car sees salted winter road conditions and most BBKs don't have dust boots to keep out debris. I suppose I could swap to/from a BBK depending on the season.

[Monkey Throttle]

Just got back from two days at AutoClub (California SuperSpeedway.) Before going to the track, I replaced the OEM brake fluid with Castro SRF and installed EndlessUSA ME20 brake pads.
What I noticed most was a complete and total lack of consistency when it came to brake pedal travel. On some turns, the brake pedal would travel very far before I felt bite. But when it bit, it bit HARD. Other turns I would get bite at the top of the Pedal.

It never seemed as though my brake force was compromised, only the amount of pedal travel I needed to engage it... Which I will say, makes Heel N Toe downshifting a little more sketchy because of the muscle memory in brake travel doesn't exist.

I did also find however the problem seemed much worse on day 1 than it did on day 2. As I was becoming smoother and more comfortable with my lines and not being so sloppy with my footwork, the pedal seemed to have more consistency and more bite at the top.

Would I prefer to have consistent brake feel without care for my technique? Yes. Did I find that driving more skillfully helped? Also, yes.

My conclusion, the brakes worked great even with odd distances in the pedal engagement. I'm sure it will screw with my confidence but the ///M didn't seem to care. It still got the job done.

I'm sure I'll be complaining about this angrily for the next few years too though. Maybe I should have bought a 911. lol.

[melanthius]

Originally Posted by Monkey Throttle

Just got back from two days at AutoClub (California SuperSpeedway.) Before going to the track, I replaced the OEM brake fluid with Castro SRF and installed EndlessUSA ME20 brake pads.
What I noticed most was a complete and total lack of consistency when it came to brake pedal travel. On some turns, the brake pedal would travel very far before I felt bite. But when it bit, it bit HARD. Other turns I would get bite at the top of the Pedal.

It never seemed as though my brake force was compromised, only the amount of pedal travel I needed to engage it... Which I will say, makes Heel N Toe downshifting a little more sketchy because of the muscle memory in brake travel doesn't exist.

I did also find however the problem seemed much worse on day 1 than it did on day 2. As I was becoming smoother and more comfortable with my lines and not being so sloppy with my footwork, the pedal seemed to have more consistency and more bite at the top.

Would I prefer to have consistent brake feel without care for my technique? Yes. Did I find that driving more skillfully helped? Also, yes.

My conclusion, the brakes worked great even with odd distances in the pedal engagement. I'm sure it will screw with my confidence but the ///M didn't seem to care. It still got the job done.

I'm sure I'll be complaining about this angrily for the next few years too though. Maybe I should have bought a 911. lol.

Double tap your brakes. Press once quick and hard to seat the pads, then second press is the actual braking zone.

[Monkey Throttle]

Originally Posted by melanthius

Double tap your brakes. Press once quick and hard to seat the pads, then second press is the actual braking zone.

You would think by 2018 if BMW could figure out how to auto blip a 6MT so you match revs on a downshift, they would also be able to figure out how to give you consistent brake pedal travel at the track.

[EGbeater]

Originally Posted by melanthius

I've been thinking along similar lines.

I've done the stainless pistons, high temp seals, dust boots, and titanium shims. Stainless lines and fluid of course. Getting air out is totally mandatory.

I feel this will get me some more life out of OEM system at the track before blowing my budget on BBK.

Not sure why but on this car almost nothing I do makes the brakes feel amazing. When I used to have my 350Z back in the day, after similar brake upgrades I had a rock solid pedal and amazing feel. Maybe its this calibration thing. No idea.

melanthius, I'm assuming you mean the Racing Brake SS pistons for OEM F8x caliper application?

https://racingbrake.com/bb-43p/ (front, currently $266/set)
https://racingbrake.com/bb-22p/ (rear, currently $133/set)

Do you remember if you perceived a significant improvement in # of laps before the fluid started to boil, or even better brake pedal feel/firmness on the lap before a soft pedal/overheated fluid condition eventually occurred?

I asked Racing Brake today "Has Racing Brake ever conducted any controlled-condition tests regarding the difference in radiated heat over time through a RB stainless piston to brake fluid, vs a representative same-sized, flat-faced aluminum caliper piston?" and they just sent me a link to this page of marketing copy and low-res pictures of OEM brake calipers/busted-up pistons devoid of any actual testing/validation of concept and execution...

https://racingbrake.com/why-rb-stainless-steel-piston/

I found this claim of performance advantage on that page particularly amusing:

Advantage of a thin wall cut stainless steel piston vs. straight cut: weight saving - Lighter wt means quicker brake response in braking and release.

Originally Posted by D_SheerDrivingPleasure

I plan to squeeze all the juice out of the OEM calipers before going BBK.

stage 1 - remove dust shield ($0)

stage 2 - install a two piece rotor ($2400 for both axles)

stage 3 - install stainless steel pistons, high temp seals and dust boots ($600 for both axles)

stage 4 - remove any air from system

Can we call this a small brake kit?

D_SheerDrivingPleasure, have you installed SS caliper pistons in your OEM brakes as planned?

If so, have you tracked the car with the new stainless pistons yet... and can you please share your experience (was there any perceived benefit)?

To be clear, I'm planning on ordering the RB stainless steel pistons anyway, because the concept seems valid and it's fairly low cost, if it even gains me an extra half hotlap (less than 60 seconds at my home track) per session before my overheated brakes fade my confidence going into the corners @ 10/10ths...

[D_SheerDrivingPleasure]

I installed the ss pistons + girodiscs in October and did several track days with them, including 2 days at WGI which is pretty hard on the brakes. I had complete confidence which can shave time...nothing is worse that having to stand on the pedal. It's a worthwhile upgrade for a dual duty car and/or if your taking baby steps.

Also, make sure you get the high temp seals and dust boots. They didn't turn to ash like the OEM ones.

Edit: A faster driver could easily overwhelm this setup. I'm kind if a granny. For reference, I'm 5 plus seconds slower that the Spanish Stig at WGI. He's 2:06 on 200tw tires.