Brake pedal feel. Soft?

alindquist · 08-15-2021, 06:30 AM

How is your brake pedal?

No matter how I bleed and what I do I can't get the pedal getting as stiff as I want, it's a bit soft and has way to long travel. I bleed it with INPA.

My 135I is more or less a track car, current setup is:

Stainless pistons both front and rear.
Braided lines.
RBF660 Fluid.
Pagid RSL29 pads both front and rear.

All brake / saftey nonsens programmed off.
The pedal feel got way better after I programmed it, but still crap. Way to bad to trust it fully on track.

Do you feel the same?

tracer bullet · 08-15-2021, 09:12 AM

I'm quite sure you know the obvious things - a chance you didn't get the air out, or an actual master cylinder issue of some sort. After that... Do you have an opportunity to drive other 135i's for comparison? There's a chance your pedal is as good as it can get with the car and it just doesn't meet your expectations?

alindquist · 08-15-2021, 10:04 AM

Quote:

Originally Posted by tracer bullet

I'm quite sure you know the obvious things - a chance you didn't get the air out, or an actual master cylinder issue of some sort. After that... Do you have an opportunity to drive other 135i's for comparison? There's a chance your pedal is as good as it can get with the car and it just doesn't meet your expectations?

Yeah, but it's good that you mention it. I've tried bleeded the system in various ways, and several times and it doesn't help.
I've been thinking of the master cylinder, maby swap it for a m3 one.

When the car is turned off, the pedal is as stiff as I want it. But asap I start it, it gets softer and when I press is really hard it sinks slowly slowly...

Yes, that's a fact. I don't know if this actually is a "good" pedal feel in this platform.

NorthernDancer · 08-15-2021, 12:47 PM

If it's a track car, are there not many others at the track who could offer advice too? I use a pressure bleeder and have never had a problem. About 250-300 ml out of each rear, 150 out of right front and 100ml out of left front.

iminhell1 · 08-15-2021, 06:35 PM

So if feel with no vacuum assist is what you like, just reduce the vacuum assist with a restrictor.

mindspin311 · 08-15-2021, 07:28 PM

If the pedal initially gets hard, then sinks as you maintain that pedal pressure, then most likely your master cylinder is failing. No need to upgrade, just replace.

MAMSport · 12-22-2021, 09:43 PM

Quote:

Originally Posted by mindspin311

If the pedal initially gets hard, then sinks as you maintain that pedal pressure, then most likely your master cylinder is failing. No need to upgrade, just replace.

While I agree this is true in some cases, for me (128i with performance brakes and at the time, 40k miles), I complained about a dropping brake pedal under constant pressure as well as some 'mushiness'. Both the dealership and my indy said 'normal operation'. It wasn't until I had the indy replace rotors and pads on all 4 corners that things improved. The solution? Bleeding the ABS sensor. I'm going to speculate that, when the perf. brakes were installed by the prior owner and by 'professional mechanics', enough air was introduced to get to the ABS unit. Bleeding that, with the calipers, made a difference!

Good luck solving this.

wootloops · 01-12-2022, 03:32 PM

EDIT: nevermind just re-read your post and noticed you said it was bled with INPA.

ferocity02 · 01-20-2022, 09:29 PM

How did you bleed the brakes? The best way is the traditional 2 person method. This method more aggressively forces fluid through the system and helps drive out air bubbles.

I bled my wifes car ( Volso S70) my 3 times via the vacuum method and the pressure method and still had a soft pedal. Then I grabbed the wife and did it the normal way and sure enough a bunch of air came out and the pedal was firm again.

MAMSport · 03-05-2022, 11:24 AM

Quote:

Originally Posted by iminhell1

So if feel with no vacuum assist is what you like, just reduce the vacuum assist with a restrictor.

Would you be kind enough to detail your suggestion of adding a vacuum restrictor?

I had my brakes bled recently, and the pedal is mushy again, not like it was immediately after the installation of new rotors and EBC red stuff pads a couple years ago. The explanation I received had to do with losing vacuum (there is a vacuum pump instead of running vacuum off the intake?). Whatever the explanation is, why do the brakes feel different after a bleed? The tech said he'd rebleed the brakes if I wanted (I went through this many times prior to the new brakes a couple years ago) but that, in his opinion, they were quite fine and no air in system.

chris82 · 03-22-2022, 10:32 AM

I have a 128i that I track often and I've struggled with a consistent firm pedal.

Here's my setup
-stock calipers w/ blank rotors
-Stainless Steel brake lines (I noticed zero difference after installing these, not even placebo)
-DTC70 pads front and rear
-high temp RBF fluid

At a 3 day event Watkins Glen, I was struggling with a soft pedal a few laps in. On the second day I finally decided to have the shop at the track put new fluid in my car midday and it definitely helped, but not enough. The pedal would be pretty soft going into turn 1 and also the brake zone before the bus stop, but after that there's a long sweeping turn where my brakes had a chance to cool. In the next brake zone I had a significantly firmer pedal. My thoughts are the brakes are just getting too hot. I'm upgrading to 335i fronts and 328i rears to see how this helps out. The stock 128i brakes don't have a lot of thermal capacity. Is there any instance on track where the brakes actually feel good? Are they firm for at least a lap or two?

chris82 · 03-22-2022, 10:40 AM

Quote:

Originally Posted by alindquist

How is your brake pedal?

No matter how I bleed and what I do I can't get the pedal getting as stiff as I want, it's a bit soft and has way to long travel. I bleed it with INPA.

My 135I is more or less a track car, current setup is:

Stainless pistons both front and rear.
Braided lines.
RBF660 Fluid.
Pagid RSL29 pads both front and rear.

All brake / saftey nonsens programmed off.
The pedal feel got way better after I programmed it, but still crap. Way to bad to trust it fully on track.

Do you feel the same?

Also, stumbled across this just now, some great info in there:
https://www.essexparts.com/news-blog...n-my-track-car

HP Autosport · 05-13-2022, 03:53 PM

At a shop environment the Steirius has been the greatest electric bleeder with 10 liters of capacity. No issues for 17+ years. With so many requests for different brake fluids the Mityvac MV6840 has yield years of trouble free service and very affordable. You will not run out of fluid with this one, even when trying to flush the ABS/DSC system. If used daily, the hose will need to be replaced every 6 months.

https://www.amazon.com/Mityvac-MV684...&creative=9325

08-15-2021, 06:30 AM	#1
alindquist Enlisted Member 148 Rep 47 Posts Drives: BMW 135I Join Date: Jan 2020 Location: Sweden iTrader: (0)	Brake pedal feel. Soft? How is your brake pedal? No matter how I bleed and what I do I can't get the pedal getting as stiff as I want, it's a bit soft and has way to long travel. I bleed it with INPA. My 135I is more or less a track car, current setup is: Stainless pistons both front and rear. Braided lines. RBF660 Fluid. Pagid RSL29 pads both front and rear. All brake / saftey nonsens programmed off. The pedal feel got way better after I programmed it, but still crap. Way to bad to trust it fully on track. Do you feel the same?
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08-15-2021, 09:12 AM	#2
tracer bullet Brigadier General 2406 Rep 3,535 Posts Drives: '11 135i , '15 X3 35i Join Date: May 2011 Location: Saint Paul, MN iTrader: (1)	I'm quite sure you know the obvious things - a chance you didn't get the air out, or an actual master cylinder issue of some sort. After that... Do you have an opportunity to drive other 135i's for comparison? There's a chance your pedal is as good as it can get with the car and it just doesn't meet your expectations?
	Appreciate 0 Quote

08-15-2021, 12:47 PM	#4
NorthernDancer Colonel 848 Rep 2,276 Posts Drives: 08 Sedona 128 & 06 330xiT 6MT Join Date: Apr 2011 Location: Ottawa On Canada iTrader: (3)	If it's a track car, are there not many others at the track who could offer advice too? I use a pressure bleeder and have never had a problem. About 250-300 ml out of each rear, 150 out of right front and 100ml out of left front.
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08-15-2021, 06:35 PM	#5
iminhell1 C2H5OH 3915 Rep 2,144 Posts Drives: 2010 SG 135i auto Join Date: May 2015 Location: Darwin, MN iTrader: (1)	So if feel with no vacuum assist is what you like, just reduce the vacuum assist with a restrictor.
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08-15-2021, 07:28 PM	#6
mindspin311 Second Lieutenant 145 Rep 210 Posts Drives: BMW Join Date: Oct 2018 Location: Atlanta iTrader: (0)	If the pedal initially gets hard, then sinks as you maintain that pedal pressure, then most likely your master cylinder is failing. No need to upgrade, just replace.
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01-12-2022, 03:32 PM	#8
wootloops First Lieutenant 354 Rep 361 Posts Drives: 2013 E92 M3 Lime Rock Park Join Date: Aug 2012 Location: Jupiter, Florida iTrader: (0)	EDIT: nevermind just re-read your post and noticed you said it was bled with INPA.
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01-20-2022, 09:29 PM	#9
ferocity02 Colonel 530 Rep 2,083 Posts Drives: 2013 135is Join Date: May 2014 Location: USA iTrader: (8)	How did you bleed the brakes? The best way is the traditional 2 person method. This method more aggressively forces fluid through the system and helps drive out air bubbles. I bled my wifes car ( Volso S70) my 3 times via the vacuum method and the pressure method and still had a soft pedal. Then I grabbed the wife and did it the normal way and sure enough a bunch of air came out and the pedal was firm again.
	Appreciate 1 amg6975497.00 Quote

03-22-2022, 10:32 AM	#11
chris82 Brigadier General 827 Rep 3,856 Posts Drives: 128i Join Date: Aug 2012 Location: NY NY iTrader: (8) Garage List 2009 BMW 128i [9.80]	I have a 128i that I track often and I've struggled with a consistent firm pedal. Here's my setup -stock calipers w/ blank rotors -Stainless Steel brake lines (I noticed zero difference after installing these, not even placebo) -DTC70 pads front and rear -high temp RBF fluid At a 3 day event Watkins Glen, I was struggling with a soft pedal a few laps in. On the second day I finally decided to have the shop at the track put new fluid in my car midday and it definitely helped, but not enough. The pedal would be pretty soft going into turn 1 and also the brake zone before the bus stop, but after that there's a long sweeping turn where my brakes had a chance to cool. In the next brake zone I had a significantly firmer pedal. My thoughts are the brakes are just getting too hot. I'm upgrading to 335i fronts and 328i rears to see how this helps out. The stock 128i brakes don't have a lot of thermal capacity. Is there any instance on track where the brakes actually feel good? Are they firm for at least a lap or two?
	Appreciate 0 Quote

05-13-2022, 03:53 PM	#13
HP Autosport Supreme Allied Commander 3837 Rep 54,338 Posts Drives: F80 M3 Join Date: Mar 2007 Location: Santa Barbara, AP, Brembo, GIAC, Koni, Ohlins, Performance Friction, www.hpautosport.com iTrader: (36)	At a shop environment the Steirius has been the greatest electric bleeder with 10 liters of capacity. No issues for 17+ years. With so many requests for different brake fluids the Mityvac MV6840 has yield years of trouble free service and very affordable. You will not run out of fluid with this one, even when trying to flush the ABS/DSC system. If used daily, the hose will need to be replaced every 6 months. https://www.amazon.com/Mityvac-MV684...&creative=9325
	Appreciate 0 Quote