Brake pedal issues. - Page 2

_Nathan_ · 21-06-2011, 11:11 AM

BMW Motorsport ABS is a bloody nightmare. Don't think it costs anywhere near that much but the software is incomprehensible and the documentation is rubbish.

The actual unit is Conti Teves MK60 so same as road car but different software.

From what I have seen so far Bosch far, far better, and far cheaper than the prices you have given. On the fly adjustment too via a driver controled switch allowing them to select from different settings for different conditions. Documentation and support a world apart.

NZ_M3 · 21-06-2011, 11:19 AM

I run the Alcons in my car and have a friend here locally that recently installed the APs and I had the pleasure of driving his car on the track in anger, I cannot for the life of me discern any noticeable differences in pedal travel between the two (if anything the Alcons probably had shorter pedal travel), I would actually say that the two kits are quite comparable and very similar in performance. I will admit however that there is a slightly appreciable difference in overall brake balance, but hardly anything I would call substantial.

If you look at the maths between the two brake kits in contrast to the factory setup, you'll realise there's very little change in terms of brake bias and overall piston volume (i.e. the fluid being moved within the calipers) - let me give you some facts to go on:

Stock CSL front brake piston area: 54.7cm2
Alcon front brake piston area: 56cm2
AP front brake piston area: 50.1cm2

Stock CSL Rear brake piston area: 33.2cm2
Alcon rear brake piston area: 32.2cm2
AP rear brake piston area: 22.9cm2

So as you can see, the Alcons do move slightly more fluid, but hardly anything outside of the working bias range between the stock set up.

The stock brakes have a front to rear bias ratio of 1.73:1
The Alcons have a front to rear bias ratio of 1.78:1
The APs have a front to rear bias ratio of 1.69:1

I am putting it down to a worn master cylinder or incorrect bleeding causing your pedal travel woes - I've had my kit for a while now and I have certainly NEVER experienced that you or Lawsy have claimed to have experienced.

Don't get me wrong, the APs are great, and if I get to do it again I would probably pick the APs over the Alcons (for more brake pad options and easier pad change), but the two kits really are quite comparable.

manos///3 · 21-06-2011, 02:57 PM

Very useful information from you guys! Thanks!

The other question is what will happen if i remove dsc -and abs of course- ?
Master cylinder straight to calipers.

I never use dsc in track and abs never intervenes on dry conditions.

**alexk** · 24-06-2011, 12:50 PM

Hi Mano,

The brake area values that NZ_M3 has shared, show a lot.
The smaller the area is, the less fluid you need to move the pads for the same distance.
The less fluid you need, the less brake travel you need.

You could deal with your problem by putting a master cylinder with bigger piston diameter.
Maybe a unit from X5 or 7 series is bigger, but you need to be sure that the dimensions are compatible with the E46.

Removing the DSC unit from a road car (with normal road loom) is a bad idea in my opinion.
You will get a lot of errors from the DSC module, issues with the sensors and possibly SMG issues (it's using input from the DSC speed sensors on the wheels).

But going back to the basics, who did the brake bleeding and how ?
As I have explained in other posts, in order to do proper bleeding in the E46 (especially when changing calipers / lines that the DSC unit runs out of fluid) you need to use the GT1 diagnostic unit and open/close the valves of the DSC unit.

manos///3 · 24-06-2011, 01:48 PM

Hi Alex,
I did the brake bleeding using the gt1 twice!
I know the procedure with dsc.

I will make a research for bigger master cylinders.

Thanks!

leaded · 17-03-2013, 01:27 AM

Did anyone get any further finding a bigger BMW master cylinder for the alcon kits?

The Gorilla · 17-03-2013, 12:52 PM

Hi,

Having now driven a E46 M3
with full Alcon Brake kit the difference
in the initial Brake bite is very
noticeable, compared to the full AP,
even more so when you get both
sets really hot.

What could work for the Alcon set up is
to fit Brake residule valves in the hard lines
just before the flexi ones.

A residule valve will reduce the amount
a caliper piston backs off and should give
a much more responsive pedal bite on
initial pedal.

They maintain a higher line pressure which
should reduce pedal travel.

Will not alter anything else, but should
hopefully reduce pedal travel and give a
tighter feel to the Brake pedal.

2lb Valves should do it as the M/C is way
above the Calipers.

www.compbrake.com/residual-valve-each.html

Regards,

The Gorilla.

leaded · 17-03-2013, 01:07 PM

Thanks for the reply.

Like you say on track or once they are hot it is even worse. Why are the APs better, do you think they might have some sort of residual valve built in to the caliper already?

There is a chap in the USA that has started to investigate a Z8 master cylinder - Part # 34-31-675-48-801 which has 27mm primary and 20mm secondary bores. This could work but a bit more plumbing and T pieces is needed to incorporate the DSC fittings. (stock BMW E46 M3 brake master cylinder is a tandem unit with a 25mm primary(front) bore and a 20mm secondary(rear) bore)

I have asked my BMW parts guy if it is possible to look at the specs of some other master cylinder to see if there is anything more suitable. E90 M3, E90 M3 GTS, X5, E60 M5/M6 or even newer cars.

Might give those residual valves a go first. Thanks for the link.

The Gorilla · 17-03-2013, 01:35 PM

Hi,

Quote - ''Why are the APs better, do you think they might have some sort of residual valve built in to the caliper already?

It was more likely due to the fact that
the AP Calipers piston size/fluid transfer was almost
on the money where as the Alcon ones
are a little oversized.

These kits are produced by and large from 'stock' calipers
so its a case of making what exists fit the
requirement.

Both the AP and the Alcon calipers are not
just specific to BMW 46's.

As a matter of interest have you actually
measured how much the Pads in your
Alcon Calipers back off ?

The problem with altering the M/C
size is that it will alter the pedal ratio.
Which brings another set of issues.

Regards,

The Gorilla.

shane@mbtech · 17-03-2013, 02:28 PM

Notice my comments on the first page.

After noting this I started to left foot tap the brake ever so slightly just before braking properly. I know lots of race drivers do this, and for me the pedal felt superb.

It's the pads backing off which is causing the issue, so the little tap gets them sitting back close to the disc. Then when back on the brake pedal it was great.

21-06-2011, 11:11 AM	#11
_Nathan_ Driving it like I nicked it Join Date: Sep 2008 Posts: 2,099 Casino cash: $13060	BMW Motorsport ABS is a bloody nightmare. Don't think it costs anywhere near that much but the software is incomprehensible and the documentation is rubbish. The actual unit is Conti Teves MK60 so same as road car but different software. From what I have seen so far Bosch far, far better, and far cheaper than the prices you have given. On the fly adjustment too via a driver controled switch allowing them to select from different settings for different conditions. Documentation and support a world apart. __________________ Nathan

24-06-2011, 12:50 PM	#14
alexk Driving it like I nicked it Join Date: Mar 2009 Posts: 2,784 Casino cash: $29969	Hi Mano, The brake area values that NZ_M3 has shared, show a lot. The smaller the area is, the less fluid you need to move the pads for the same distance. The less fluid you need, the less brake travel you need. You could deal with your problem by putting a master cylinder with bigger piston diameter. Maybe a unit from X5 or 7 series is bigger, but you need to be sure that the dimensions are compatible with the E46. Removing the DSC unit from a road car (with normal road loom) is a bad idea in my opinion. You will get a lot of errors from the DSC module, issues with the sensors and possibly SMG issues (it's using input from the DSC speed sensors on the wheels). But going back to the basics, who did the brake bleeding and how ? As I have explained in other posts, in order to do proper bleeding in the E46 (especially when changing calipers / lines that the DSC unit runs out of fluid) you need to use the GT1 diagnostic unit and open/close the valves of the DSC unit. __________________ www.clubcsl.com - I am a BMW Motorsport fan ! My youtube channel is here

21-06-2011, 11:19 AM	#12
NZ_M3 S5, Sport On, DSC M-track Join Date: Jun 2008 Location: Auckland, New Zealand Posts: 1,434 Casino cash: $13579	I run the Alcons in my car and have a friend here locally that recently installed the APs and I had the pleasure of driving his car on the track in anger, I cannot for the life of me discern any noticeable differences in pedal travel between the two (if anything the Alcons probably had shorter pedal travel), I would actually say that the two kits are quite comparable and very similar in performance. I will admit however that there is a slightly appreciable difference in overall brake balance, but hardly anything I would call substantial. If you look at the maths between the two brake kits in contrast to the factory setup, you'll realise there's very little change in terms of brake bias and overall piston volume (i.e. the fluid being moved within the calipers) - let me give you some facts to go on: Stock CSL front brake piston area: 54.7cm2 Alcon front brake piston area: 56cm2 AP front brake piston area: 50.1cm2 Stock CSL Rear brake piston area: 33.2cm2 Alcon rear brake piston area: 32.2cm2 AP rear brake piston area: 22.9cm2 So as you can see, the Alcons do move slightly more fluid, but hardly anything outside of the working bias range between the stock set up. The stock brakes have a front to rear bias ratio of 1.73:1 The Alcons have a front to rear bias ratio of 1.78:1 The APs have a front to rear bias ratio of 1.69:1 I am putting it down to a worn master cylinder or incorrect bleeding causing your pedal travel woes - I've had my kit for a while now and I have certainly NEVER experienced that you or Lawsy have claimed to have experienced. Don't get me wrong, the APs are great, and if I get to do it again I would probably pick the APs over the Alcons (for more brake pad options and easier pad change), but the two kits really are quite comparable.

21-06-2011, 02:57 PM	#13
manos///3 S2 - Picking it up Join Date: May 2011 Location: Greece Posts: 42 Casino cash: $828	Very useful information from you guys! Thanks! The other question is what will happen if i remove dsc -and abs of course- ? Master cylinder straight to calipers. I never use dsc in track and abs never intervenes on dry conditions.

24-06-2011, 01:48 PM	#15
manos///3 S2 - Picking it up Join Date: May 2011 Location: Greece Posts: 42 Casino cash: $828	Hi Alex, I did the brake bleeding using the gt1 twice! I know the procedure with dsc. I will make a research for bigger master cylinders. Thanks!

17-03-2013, 01:27 AM	#16
leaded S3 - On the open road Join Date: Nov 2011 Posts: 83 Casino cash: $2452	Did anyone get any further finding a bigger BMW master cylinder for the alcon kits?

17-03-2013, 12:52 PM	#17
The Gorilla S5, Sport Off, DSC M-track Join Date: Apr 2008 Posts: 740 Casino cash: $14401	Hi, Having now driven a E46 M3 with full Alcon Brake kit the difference in the initial Brake bite is very noticeable, compared to the full AP, even more so when you get both sets really hot. What could work for the Alcon set up is to fit Brake residule valves in the hard lines just before the flexi ones. A residule valve will reduce the amount a caliper piston backs off and should give a much more responsive pedal bite on initial pedal. They maintain a higher line pressure which should reduce pedal travel. Will not alter anything else, but should hopefully reduce pedal travel and give a tighter feel to the Brake pedal. 2lb Valves should do it as the M/C is way above the Calipers. www.compbrake.com/residual-valve-each.html Regards, The Gorilla.

17-03-2013, 01:07 PM	#18
leaded S3 - On the open road Join Date: Nov 2011 Posts: 83 Casino cash: $2452	Thanks for the reply. Like you say on track or once they are hot it is even worse. Why are the APs better, do you think they might have some sort of residual valve built in to the caliper already? There is a chap in the USA that has started to investigate a Z8 master cylinder - Part # 34-31-675-48-801 which has 27mm primary and 20mm secondary bores. This could work but a bit more plumbing and T pieces is needed to incorporate the DSC fittings. (stock BMW E46 M3 brake master cylinder is a tandem unit with a 25mm primary(front) bore and a 20mm secondary(rear) bore) I have asked my BMW parts guy if it is possible to look at the specs of some other master cylinder to see if there is anything more suitable. E90 M3, E90 M3 GTS, X5, E60 M5/M6 or even newer cars. Might give those residual valves a go first. Thanks for the link.

17-03-2013, 01:35 PM	#19
The Gorilla S5, Sport Off, DSC M-track Join Date: Apr 2008 Posts: 740 Casino cash: $14401	Hi, Quote - ''Why are the APs better, do you think they might have some sort of residual valve built in to the caliper already? It was more likely due to the fact that the AP Calipers piston size/fluid transfer was almost on the money where as the Alcon ones are a little oversized. These kits are produced by and large from 'stock' calipers so its a case of making what exists fit the requirement. Both the AP and the Alcon calipers are not just specific to BMW 46's. As a matter of interest have you actually measured how much the Pads in your Alcon Calipers back off ? The problem with altering the M/C size is that it will alter the pedal ratio. Which brings another set of issues. Regards, The Gorilla.

17-03-2013, 02:28 PM	#20
shane@mbtech CSL Register Uber-poster! Join Date: Feb 2009 Location: warrington Posts: 5,419 Casino cash: $19783	Notice my comments on the first page. After noting this I started to left foot tap the brake ever so slightly just before braking properly. I know lots of race drivers do this, and for me the pedal felt superb. It's the pads backing off which is causing the issue, so the little tap gets them sitting back close to the disc. Then when back on the brake pedal it was great.