[renizer]

hey there,
so I replaced the corroded stock discs on my rear axle with some EBC turbo groove discs and EBC RedStuff pads and managed to snap off the cable going to the pad wear sensor (or switch?). i didn't have time to fix the cable that night so i drove a couple of days without it, of course had the "brake pads worn, change them" screen in my idrive and here's the thing:
i had instantly noticed a very nice boost in immediate brake response, as i always found the pedal kinda sluggish in this car. i know the brakes have yet to break in and i'm treating them accordingly, but i attributed it first to the new parts (rear only, front not done yet).

anyways, yesterday i fixed the cable and the message in idrive is gone.....however, so is that nice "immediate" brake response feel!
what electronic function of the brake system is that attributable to and how could this possibly be coded away so it always feels this nice?
maybe more a coding question but just wondering if anyone else has maybe experienced this or if the reason to this whole behaviour is maybe completely different..
thanks in advance for all inputs,
greetz
Andi

[feuer]

Read here: http://www.onelapx1.com/blog/how-to-...w-actually-fun I would say Brake Standby (EVB) and Maximum Brake Support (HVV) is what you are after.

[juld0zer]

Must be some sort of unofficial wear compensation feature where it assumes worst case scenario being metal on metal and relaxes the modulator's valves to allow more fluid pressure.

There's no documentation to support this theory but I have noticed it also.

[mweisdorfer]

Originally Posted by renizer

hey there,
so I replaced the corroded stock discs on my rear axle with some EBC turbo groove discs and EBC RedStuff pads and managed to snap off the cable going to the pad wear sensor (or switch?). i didn't have time to fix the cable that night so i drove a couple of days without it, of course had the "brake pads worn, change them" screen in my idrive and here's the thing:
i had instantly noticed a very nice boost in immediate brake response, as i always found the pedal kinda sluggish in this car. i know the brakes have yet to break in and i'm treating them accordingly, but i attributed it first to the new parts (rear only, front not done yet).

anyways, yesterday i fixed the cable and the message in idrive is gone.....however, so is that nice "immediate" brake response feel!
what electronic function of the brake system is that attributable to and how could this possibly be coded away so it always feels this nice?
maybe more a coding question but just wondering if anyone else has maybe experienced this or if the reason to this whole behaviour is maybe completely different..
thanks in advance for all inputs,
greetz
Andi

Brake pads take anywhere from 500 to 1000 miles to fully brake in depending on the material in the pad. Did you burnish the new pads to the new rotors? When I say burnish, I mean speed up to 60 mph and brake hard, but not hard enough to set off the ABS system, down to 15mph. Do this 8x in a row.

Did you bleed the brakes correctly? The Bentley Repair Manual has a very specific method for this.

[renizer]

Hey everybody,
hope you all had a good start into 2019 & thanks for your input.

feuer, thanks for the link! i had read that article some time ago before and that's what actually made me think of the coding options for the brake functions.. need to look into that again and maybe get into some coding. Have to read the article again to look at these 2 functions you suggest!

juld0zer, yeah I thought about the same.. think it's assuming worst case scenario and thereby applying full pressure as you say. felt nice though as said and more linear...probably what feuer's suggestion would yield?!

mweisdorfer, no i did not do any burnishing yet, i just got done doing about 800km now since the brake change so I will do that soon now, similar to what you decribe is more or less what the brake manufacturer (EBC) suggests.
I did not bleed the brakes though, not absolutely needed in my opinion for swapping out discs and pads? However, I will do a flush and fluid replacement next spring anyways since it's been about 2 years now.

[TheMidnightNarwhal]

Originally Posted by renizer

hey there,
so I replaced the corroded stock discs on my rear axle with some EBC turbo groove discs and EBC RedStuff pads and managed to snap off the cable going to the pad wear sensor (or switch?). i didn't have time to fix the cable that night so i drove a couple of days without it, of course had the "brake pads worn, change them" screen in my idrive and here's the thing:
i had instantly noticed a very nice boost in immediate brake response, as i always found the pedal kinda sluggish in this car. i know the brakes have yet to break in and i'm treating them accordingly, but i attributed it first to the new parts (rear only, front not done yet).

anyways, yesterday i fixed the cable and the message in idrive is gone.....however, so is that nice "immediate" brake response feel!
what electronic function of the brake system is that attributable to and how could this possibly be coded away so it always feels this nice?
maybe more a coding question but just wondering if anyone else has maybe experienced this or if the reason to this whole behaviour is maybe completely different..
thanks in advance for all inputs,
greetz
Andi

Here is a quote from EBC redstuff website

"Redstuff brake pads are however as a harder compound does take longer to fully bed in to achieve its highest levels of performance (can be up to 1000 miles/1600 Kms urban use)"


I get what you mean, I changed my brakes and rotors and the feel was definitely different. Bleed brakes and had soft pedal issue (I think because I didn't do the whole ABS module bleeding with it) but now like ~ 500KM in everything feels good and nice.

[renizer]

No offense Midnight but I think you got my OP wrong. I was saying I think the brake feeling was nicer due to some software function being activated/working differently with the broken pad wear sensor cable. When I fixed the cable, that was gone.
However the brakes feel a bit nicer after the change at least, and I guess will continue to do so with the progress of bed in still need to do that burnishing procedure though.

[TheMidnightNarwhal]

Originally Posted by renizer

No offense Midnight but I think you got my OP wrong. I was saying I think the brake feeling was nicer due to some software function being activated/working differently with the broken pad wear sensor cable. When I fixed the cable, that was gone.
However the brakes feel a bit nicer after the change at least, and I guess will continue to do so with the progress of bed in still need to do that burnishing procedure though.

Ah I'm sorry my bad.

That's an interesting theory/remark.

I had driven with my rear sensor broken for a week before I fixed it and did not notice any changes. Rear brakes are small tho so.

But I don't see in the whole picture why the car would matter if you have a sensor or not.

[renizer]

No prob.. In my case it was a night and day difference. And it makes sense to me to, just as juld0zer pointed out, if it does not have any information about pad wear, it will fall back to the worst case scenario which is either assuming no friction material is left, or either disabling some brake functions what in result yields full brake pressure. After all it's not just how hard you hit the brakes but more a matter of how software commands the brake line pressure

[rich_mane]

I've noticed these functions before in my braking.. I never have taken it to the track but any time I lift-off after a pull, the brakes are always more responsive. I knew that was a feature of the car pre-tensioning the brakes, but I didn't know about a lot of those other assists.

I might have to dig into that article some more and maybe do some coding to see what feels best. Thanks for the link feuer.

[renizer]

indeed, really nice detailing there in that link and worth the time to play around with it I guess feuer or someone else who might know, are these all the same for the N55 (xDrive)? it says N54 so I guess yes but maybe someone can answer that for sure. Also, are there different DSC or Brake System controller hardware versions or sth if that's a separate one?

[juld0zer]

Xdrives use a Bosch DSC module. RWDs use an ATE module. They do things differently but most of the features are available in both. The commonly accessible info applies to the ATE/RWD models, however. There is no documentation describing how/if the Bosch module supports these features.

Rich_mane, that is the ready alert brake feature. If your module allows, you can code it off. It is under "RAB" from memory

[bbnks2]

There is most definitely some sort of brake line pressure factor attributed to estimated brake pad wear. I think it only applies to DSC functions though. Meaning, things like "brake-pretension" would be affected by brake pad sensor estimates.

Makes sense... pre-tensioning the brakes requires different travel with full pads than they do with 2mm pads... Obviously you need to account for that if you want that function to pre-tension the brakes consistently.

I don't believe at all though that this affects normal braking. This is in relation purely to when those DSC functions intervene in your driving. I have most of those things coded out and my brake peddle requires significantly more travel when the pads are low. New pads gives me a nice firm pedal at the top of travel again.

[juld0zer]

Pretensioning should require the same volume of fluid whether the pads are 1000km old or worn to the last 25%. Disc brakes are self adjusting and this is one of the benefits. Unless there is a piston seal issue that draws the piston back more when the piston is almost at full excursion (which is not rare).

The pedal has become just a way to tell the computer we want to stop. The electronics do the rest. This is actually what they did in the new X5. Scary times ahead!

[bbnks2]

Originally Posted by juld0zer

Pretensioning should require the same volume of fluid whether the pads are 1000km old or worn to the last 25%. Disc brakes are self adjusting and this is one of the benefits. Unless there is a piston seal issue that draws the piston back more when the piston is almost at full excursion (which is not rare).

The pedal has become just a way to tell the computer we want to stop. The electronics do the rest. This is actually what they did in the new X5. Scary times ahead!

Bad example but BMW is definitely using estimated brake pad wear for various DSC functions. It shouldn't have anything to do with regular braking though like people claimed. Brake pre-tensioning doesn't happen every time you lift off the pedal... only in panic situations like accelerating to beat a yellow light and then lifting off the gas abruptly when you realize you won't make it. You'll be met with a nice firm pedal.

[renizer]

Hmm, so all brake functions are in the DSC / DXC modules huh? Interesting thought, there might indeed be some small differences in that regard between RWD and xDrive models then. And maybe some differences are also only in the coding between the two..
But as you say, with regular, slight braking this shouldn't have any effect anyhow! Interesting...I could swear I felt that even just feathering it, driving down the slight compression from my workshop. Doing the same after fixing that pad wear sensor cable, the brakes felt completely different.

I think what juld0zer said about the hydraulic compensation of the pad wear makes sense as far as the additional "travel" goes. But maybe they are also compensating for worse friction coefficient, reduced pad effect or something like that, so I could see a slightly higher line pressure reasonable.

However, I still think the case I experienced was simply a "full retard" fallback to worse case assumption of 'metal-on-metal' braking without the pad sensor info.

[bbnks2]

Originally Posted by renizer

Hmm, so all brake functions are in the DSC / DXC modules huh? Interesting thought, there might indeed be some small differences in that regard between RWD and xDrive models then. And maybe some differences are also only in the coding between the two..
But as you say, with regular, slight braking this shouldn't have any effect anyhow! Interesting...I could swear I felt that even just feathering it, driving down the slight compression from my workshop. Doing the same after fixing that pad wear sensor cable, the brakes felt completely different.

I think what juld0zer said about the hydraulic compensation of the pad wear makes sense as far as the additional "travel" goes. But maybe they are also compensating for worse friction coefficient, reduced pad effect or something like that, so I could see a slightly higher line pressure reasonable.

However, I still think the case I experienced was simply a "full retard" fallback to worse case assumption of 'metal-on-metal' braking without the pad sensor info.

"dsc" module is actually an "ABS" module which has advanced over years to support robust stability control functions.

[renizer]

You're absolutely right... Seems it has advanced so much I now didn't think of it in that way back to its source LOL

[CIDCrazyJay]

Just came across this thread searching for "brake pad wear compensation" after finding said value in NCS Dummy yesterday.

It appears you may be able to change the value to another predetermined setting, create your own custom value, or even disable the feature completely by selecting the "00" option.

These images are for this 2011 128i MSport M6sp.

NCS Dummy Refresher;
"Mask" is the range of acceptable values
"Data" is the current selection

[renizer]

CIDCrazyJay interesting, so you're thinking with the wear sensor not attached and the DTC active for that, it would probably disable this compensation at all?