E90Post
 


TNT Racewerks
 
BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Suspension | Brakes | Chassis > Alcon BBK - strange feeling of pedal



Reply
 
Thread Tools Search this Thread
      07-16-2014, 04:14 AM   #1
PiciuM
New Member
PiciuM's Avatar
2
Rep
13
Posts

Drives: 2012 IS-F, ex-e90 330i
Join Date: Dec 2013
Location: Poland/Czech Republic

iTrader: (0)

Alcon BBK - strange feeling of pedal

I've had my Alcon BBK installed on my 330i and the brake pedal behaves in rather strange way:
- I only have front BBK and front steel lines - standard pad there, sth like ferodo DS
- rear is OEM with more aggresive pads
- before the track day I've had break liquid bleeded - pedal feel was perfect, I was driving like 1000km on public roads and it was always good

Then on the track:
- sometimes pedal was feeling perfect from the top, brakes were grabbing great and 1 corner after pedal was feeling meshy and going much deeper - I had to press it for the second time in order to get good bite
- this situation happened many times and it was terrible, as I couldn't get my braking points to maximum as I never knew if it will grab properly from the 1st hit or I need to press it again - on the Nordschleife this is crazy scary

Test on the road:
- when was going to refuel I was driving on the straight road, tried 3 times and always pedal felt perfect from the first hit. Then I did relatively quick left,right, left and tried again - pedal went much deeper together with meshy feel, as if there was air???

Any idea what it can be?
- still some air left - in this case movement of the car can influence the pedal feel?
- absence of middle and rear steel lines?
- sth else?
- I assume this was NOT due to the front pad fade, as it was either good or bad, never anything between, like on/off feeling and it was changing from 1 corner to another...

Thanks for any suggestions - I spent lots of money and I'm not happy .
I asked Alcon rep to call me, waiting...
__________________
2012 IS-F - OEM for the moment
2007 e90 330i, M package, K&N, M performance exhaust and front strut bar, quaife, Alcon BBK - SOLD
Appreciate 0
      07-16-2014, 01:01 PM   #2
3002 tii
Lieutenant General
3002 tii's Avatar
2272
Rep
12,559
Posts

Drives: Z4 M, X5, GX460
Join Date: Apr 2008
Location: CT

iTrader: (99)

Garage List
Those pads you're using are street pads which are not up for track duty. You probably experienced some fade even though you don't think it was. That on/off feedback was due to the brakes cooling down but after a lap or two would heat up again and pass their optimal operating temps.

Find out the pad shape of your caliper and get some track pads front and rear.
__________________
Follow for latest mods
Appreciate 0
      07-17-2014, 01:44 AM   #3
PiciuM
New Member
PiciuM's Avatar
2
Rep
13
Posts

Drives: 2012 IS-F, ex-e90 330i
Join Date: Dec 2013
Location: Poland/Czech Republic

iTrader: (0)

I know ferodo DS is not purely track pad.
But it happened already after 2-3 first corners, which were taken easily (1 lap, after long breake), so I'm sure it was not a pad fade.

I was talking with Alcon - they say there might still be some air somewhere in the system and if it is stuck e.g. in the ABS pump, traditional bleeding will not take it out.
- is there SPECIAL PROCEDURE for e90 to completely get rid of air during putting of new brake fluid? Like opening some valve etc?

Another possiblity is incorrect fitment - if caliper is not 100% in line with disc then some movements of pad might occur and it will result in some additional movement of piston in order to put pad fully to the disc - I will check it if new brake liquid won't help.
__________________
2012 IS-F - OEM for the moment
2007 e90 330i, M package, K&N, M performance exhaust and front strut bar, quaife, Alcon BBK - SOLD
Appreciate 0
      07-21-2014, 03:09 AM   #4
PiciuM
New Member
PiciuM's Avatar
2
Rep
13
Posts

Drives: 2012 IS-F, ex-e90 330i
Join Date: Dec 2013
Location: Poland/Czech Republic

iTrader: (0)

Quick update:
- I did bleeding in BMW service with full procedure for ABS pump
Result:
- no difference

Now I will check if my bearings are ok (I hear nothing wrong, but apparently if they are loose it might impact brake feel)

Any other ideas?
__________________
2012 IS-F - OEM for the moment
2007 e90 330i, M package, K&N, M performance exhaust and front strut bar, quaife, Alcon BBK - SOLD
Appreciate 0
      11-04-2019, 03:02 AM   #5
juld0zer
Lieutenant Colonel
Australia
480
Rep
1,600
Posts

Drives: Prev 135i 7DCT, Now 130i 6sp
Join Date: Jul 2016
Location: 2153

iTrader: (0)

This is an old thread I know, but did you resolve it?
It sounds like pad knockback if you can induce it by rocking the steering side to side but usually occurs on a long/fast corner.

Are the lines of ample length and not too short/too long?
Appreciate 0
      11-04-2019, 03:24 AM   #6
stevesingo
Private First Class
United Kingdom
45
Rep
163
Posts

Drives: E90 330i MSport 6MT
Join Date: Feb 2014
Location: Cumbria

iTrader: (0)

Quote:
Originally Posted by juld0zer View Post
This is an old thread I know, but did you resolve it?
It sounds like pad knockback if you can induce it by rocking the steering side to side but usually occurs on a long/fast corner.

Are the lines of ample length and not too short/too long?
This. Flex in the hubs under lateral load (more so when running sticky track tyres or slicks) cause the discs to run off centre and push the pads back. When then the load is removed, there is a gap which means you have a long travel on the pedal at first push.

To confirm, try dabbing the pedal whilst accelerating after the preceding corner on the straight. If the pedal is good in the next breaking zone, it is pad knock back.

You can fit anti knockback springs or residual pressure check valves to minimise the effect.
Appreciate 0
Reply

Bookmarks

Tags
alcon, bbk, issue, pedal feel

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 10:09 AM.




e90post
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST