Brake pedal issues.

[manos///3]

I tracked a csl with ap brakes front and rear and the pedal distance was very short and the feeling was too hard. This is what i want from my brakes.

I have Alcon csl cup kit on my car and the brake pedal isn't the same with Ap. I don't know why..I am using motul rbf 600 brake liquid and pagid rs29 pads.

Any ideas?

[karbonkid]

Alcons will give longer travel compares to APs. Im not sure what can be done here to be honest.

[DazBlackCSL]

Alcons will give longer travel compares to APs. Im not sure what can be done here to be honest.

+1

= Sell Alcons, Buy AP - :clown:

[3wheels3]

Could try RS14 or 15. IMO they have quite a bit more initial bite which may give you what you want, saying they do them for those calipers. Just an idea.

[The Gorilla]

Hi,

Has your master cylinder been bled
with a power bleeder just so
there is no air whatsoever in the system ?

Do you have a balanced set up, ie
front and rears or just fronts ?

If you have just fronts, then a 'balance valve'
to the rears might help,

If Brakes have been power bled then its-

Pedal Ratio V Brake Master cylinder size
V Caliper piston sizes V swept fluid volume.

I do not know if there is another BMW
Brake Master Cylinder which will fit
the E46 M3 Servo and is slightly smaller
size than the std M3/CSL ones,
so as to increase Brake Pedal pressure which should
in theory give the Alcons a stiffer pedal
feel.

Slight downside is that pedal pressure will have
to increase on the std fixed pedal ratio.
ie] more left foot pressure.

Regards,

The Gorilla.

[shane@mbtech]

The Alcon pedal feel is shit if I am honest. AP are far better.

The master cylinder needs changing, but as G man says, I dont know of a different one to sort this out.

Fitting a pedal box with correct sized cylinder will of course work, but major overkill in a road car.

I power bled mine in all manner of sequence, it was always the same.

But they work, so use them, they feel better for road use as they are not as snatchy as the AP, they also work great on track, but dont inspire as much confidence as the AP due to pedal feel/travel.

I have said this for a long time about the Alcons, people are slowly starting to see my point.

That said they are still far far better than stock set up for track use.

[manos///3]

I have front/rear setup.

I was thinking the solution of pedal box with two master cylinders or one with two exit hoses, as i am using the car 99% for track. But i am not sure...

Alcon brakes are excellent on track.
Ap's pedal feeling is like drive a kart!

[The Gorilla]

Hi,

Manos///3- If you go with a Bias Pedal Box
or some type of dual cylinder set up then you
will have to loose the std Brake servo
which will effect pedal ratio/ pressure for
the ABS.

Remote servo ?

While you will be able to play around with
the master cylinder sizes, and pedal ratio,
its not without its own set of issues.

No free lunch.

Regards,

The Gorilla.

[manos///3]

Gorilla without servo means that ABS should be working more often with less pedal pressure?

What are they do in motorsport world?

[The Gorilla]

Hi,

Mamos- The 'BMW MS Racing ABS' is
streets away from what you have
in your car.

The BMW MS ABS is around 8/9k if I remember
correctly.

It has variable settings for Modulation
etc.

To set up the std ABS system with
a bias pedal box arrangment and no servo
will not give a 'pedal feel' anything like
the AP's that is for sure !!!

I have never driven a M3 with Alcon Kit
but from what Lawsy and you are saying
its like there is more pedal Travel before
the bite/pedal resistance is felt ?

The std Servo / ABS system is very good
so why not fit the Brake Pedal assembly
from an Auto E46, stronger and better
pedal offset.

Then fit a Brake Bias Valve into the rear
brake line, mount the valve adjuster in the car,
centre console or whatever.

Then in the dry you can increase the front
bias which might assist with pedal feel/ response
as taking away some rear bias in the dry will
not alter very much, and then in the wet you can
give more rear bias, which is what you want
anyway.

200 or so Euros if you do it yourself.

Regards,

The Gorilla.

[_Nathan_]

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]

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]

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]

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]

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]

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

[The Gorilla]

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]

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. :beer:

[The Gorilla]

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]

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.