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Discussion Starter #1
Hi Guys,
I've been meaning to pose this question for some time now. With the recent installation of my four wheel Stop Tech BBK, I was told my a few BMW techs that the car's ABS system will no longer function as it should, simply becuase the ABS system is not calibrated to operate with the BBK. When bedding in my car's brake pads, I personally did numerous and intense hard braking slow downs, anywhere from 80-100 mph slowing the car down to approx. 20 mph. At no point in time did the ABS activate. I didn't feel the slightest pulse from the brake pedal. So...... is what the BMW techs told me true or did I not apply the BBK brakes hard enough to activate the ABS system ??? Any thoughts on this... please share them, okay.
Thank you.
PS I will also ask Dave Z. as I have a scheduled business date to meet with him in approx. one week.

:cheers:
 

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it is false. just another case of a bmw tech who really has no understanding of the system.
ABS will still work, unless you removed components, but then you'd have an abs light on the dash!

If you're unsure, find some wet ground, gravel or grass and stomp on the brake...
 

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Yes this is correct on the ABS point.

Worth adding on the subject that the brake pad wear sensor will no longer operate (or at least it doesn't with the AP BBK).
 

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rogbacon said:
Yes this is correct on the ABS point.

Worth adding on the subject that the brake pad wear sensor will no longer operate (or at least it doesn't with the AP BBK).
My stoptech kit still has the pad wear sensor.
Mike
 

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mottati said:
it is false. just another case of a bmw tech who really has no understanding of the system.
ABS will still work, unless you removed components, but then you'd have an abs light on the dash!

If you're unsure, find some wet ground, gravel or grass and stomp on the brake...
I'd like Dave Z to weigh in on this... have the BBKs been calibrated to have the same Pressure/Volume/Displacement curve as the stock set up? Or does the BMW ABS system somehow 're-calibrate' for the changed system (or are the control parameters so broad that there is no impact?)

As I understand it, the ABS control parameters take into account how quickly brakes will grab and release, and when you change this it can effect ABS performance.

Sliding on gravel or grass IS NOT like sliding on dry asphalt while trying to turn...

A
 

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Discussion Starter #8
mottati said:
My stoptech kit still has the pad wear sensor.
Mike

Mike,
Your correct with the pad wear sensor, because I saw Dave Z. showed me the pad sensors, when doing the install. But, what i want to know is does the ABS work just as if the system is stock OEM brake system or is the ABS changed in any way. :confused:
 

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Discussion Starter #9
ard said:
I'd like Dave Z to weigh in on this... have the BBKs been calibrated to have the same Pressure/Volume/Displacement curve as the stock set up? Or does the BMW ABS system somehow 're-calibrate' for the changed system (or are the control parameters so broad that there is no impact?)

As I understand it, the ABS control parameters take into account how quickly brakes will grab and release, and when you change this it can effect ABS performance.

Sliding on gravel or grass IS NOT like sliding on dry asphalt while trying to turn...

A
Ard, That basically what the BMW techs told me when i was at my BMW dealership. They basically stated that the ABS no longer operates as it did when the brakes were stock. You lose the ABS with the BBK. hmmm
 

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FAST 5 said:
You lose the ABS with the BBK. hmmm

This is a shades of grey thing, or perhaps semantics...

I believe (just my opinion, please prove me wrong) that the ABS will no longer function as designed. I believe it will actuate, but it MIGHT not have 100% of the same protection of the original system.

Then, does the increased safety of a more capable brake system outweigh this possible decrease? Does the fact that BBKs are in cars driven by talented and attentive drivers reduce this risk? (We are all in the category, BTW :) )

I'd love to hear some expert input...


A

http://www.m5board.com/vbulletin/showpost.php?p=508341&postcount=28
 

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This cannot be correct. I mean Dinan does offer a BBK. Look at it this way, an ABS system measures (using 4 sensors which are retained with the StopTech BBK) the speed at which the wheel is turning and if the rotation slows greatly, the hydraulic brake lines are pressurized and depressurized several times a second. I don't see why any of this would be affected by a BBK.

TexasM5
 

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I have the Stoptechs BBK on the fronts with 275s on rear rims and so far the ABS has worked on pavement, gravel, ice and snow...I have not gotten the opportunity to try grass yet... :1:

Mark
 

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TexasM5 said:
This cannot be correct. I mean Dinan does offer a BBK. Look at it this way, an ABS system measures (using 4 sensors which are retained with the StopTech BBK) the speed at which the wheel is turning and if the rotation slows greatly, the hydraulic brake lines are pressurized and depressurized several times a second. I don't see why any of this would be affected by a BBK.

TexasM5
In a nutshell, the BigBrake Kit MUST be designed to work with the ABS system- they are inter-related. You can't just increase caliper (and volume) without regard for the ABS controller...

Some more info:

http://www.stoptech.com/whitepapers/abs_bigbrake_122701.htm
 

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TexasM5 said:
This cannot be correct. I mean Dinan does offer a BBK. Look at it this way, an ABS system measures (using 4 sensors which are retained with the StopTech BBK) the speed at which the wheel is turning and if the rotation slows greatly, the hydraulic brake lines are pressurized and depressurized several times a second. I don't see why any of this would be affected by a BBK.
Actually, this can be affected by a big brake kit. The ABS and DSC is calibrated to expect a certain response from the brake calipers to a given change in hydraulic pressure. This response is factored in to the calibration parameters. If the stock pressure vs volume relationships are dramatically changed by a big brake kit, then the efficiency of the ABS can be reduced. The ABS will continue to operate, but it won't be as effective as it would otherwise have been. Unlike ABS, which is an adaptive, closed-loop system, dynamic stability control is open loop. I would be more concerned about the impact of a BBK on stability control.

This is the reason StopTech uses the consulting services of James Walker, JR. who is now in charge of the vehicle dynamics team at Delphi. He developed much of the ABS and stability control for the C6 Corvette and was recently promoted to run the entire organization. James helped StopTech develop a battery of tests to tune the brake system design so it works well with factory ABS and stability control systems. If you want to see these tests in action, check out my diary of a day spent track testing with StopTech nearly three years ago: http://www.zeckhausen.com/Testing_Brakes.htm.

As stability control and ABS becomes more sophisticated, it's even more important to pay attention to system interactions and test every platform to be sure you didn't actually make things worse. Some platforms are tougher than others to get right. StopTech struggled with the new Mustang platform over several test days until they finally got it right. On the other hand, the new StopTech kit for the Chrysler 300C produced dramatic reductions in 60-0, 80-0, and 100-0 stopping distances. These reductions occurred under ABS braking and were accomplished without any negative impact on the platform's stability control.

To get to the heart of this thread, the StopTech BBK fully preserves the capability of the BMW M5 ABS and stability control. StopTech has taken the performance of these systems into account when selecting the caliper piston sizes for their kits and they have verified the resulting design at the track in the same manner described in the link above for the 350Z kit.

One of the perks of my relationship with StopTech is the opportunity to attend training classes taught by James Walker on ABS and stability control performance. If you check out my "NEWS" page, you can get more details on these classes: http://www.zeckhausen.com/news.htm
 

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Yeah, what he said... :)

Plus my link above is a white paper written by Jim Walker explaining the issues...worthwhile reading IMHO.
 

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Very interesting Dave.

Youre right with everything you said.
One addition by me:
The ABS and DSC are using a pressure modell.
This pressure modell has to be adjusted for every brake model.

If you build in an aftermarket brake, this pressure model is not more correct and you are loosing performance in ABS and DSC.

But both systems are still working.
 

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Dave Z,

This board is an excellent source of technical information. I would have never thought of this before the issue was raised, but it does make sense that the ABS and DSC and XXX systems would be affected by BBK's. I appreciate the input on the Stoptech BBK's but what about the Brembo's? Do they adversely affect the factory E39 M5 ABS and stability systems?
 

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Just remember, that ABS does not help you stop in a shorter distance. Even if there is a slightly reduced effect from the ABS after a big brake kit was added, threshold braking a BBK will stop the car a lot faster than full ABS with normal brakes.
DSC? What is that? Oh yeah, it is the button I press everytime I am blessed with driving a newer BMW. :haha:
Good concerns though, as it would be terrible to change the system without knowing, and then being suprised when it didnt act as it did in the past.
:cheers:
 
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