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dfmitch
07-25-2005, 07:47 PM
I have a 2001 e46 330ci. I have driven it in three drivers schools and warped the rotors every time (once I was sharing the car with my son so I don't count that). I have stock BMW pads and rotors on. Does anyone have suggestions to avoid this- different pads, different rotors, brake cooling ducts? I don't think it's my driving. I have over 20 schools and have a 1988 325is that had original rotors for 150,000 miles and 15 schools. I also drive around the parking lot after the run to cool them off more. Has anybody had regular problems with e46 brakes on the track?

daddeu
07-25-2005, 08:27 PM
Unless you have measured the runout with a dial indicator, your rotors are probably not warped.
What you are experiencing, as I have, is variations in the the consistency of the pad/binder material deposited on the surface of the rotor during braking. These variations around the surface have different coefficients of friction, causing the pad's grip to fluctuate. Your stock pads are designed to grab the rotor surface cold or hot (not overheated), wet or dry. When you put a stock pad to use on a track with heavy brake use and the higher temperatures, the binder cooks out onto the pad surface (I'll wager you have a lot more brake dust from your pads after a track event than you had before). I recommend an intermediate pad (i.e., mid-way between street and competition) to solve the problem. I use Hawk HPS pads on my M3, followed tc kline's recomendations for bedding and have had no problems.
An alternative is to use a set of competition pads with their properly bedded rotors for track, and another set of OEM street pads and its set of properly bedded rotors for daily driving.

mlytle
07-25-2005, 08:41 PM
yup, what he said.....

with that many schools i doubt you are in the beginners group. you should be using track pads and separate rotors, or hps/r4s/cool willies at least.

1996 328ti
07-25-2005, 09:50 PM
Aren't E46 cooling ducts blocked? Or am I thinking about another car?

jkuper
07-26-2005, 11:37 AM
They are on M3s, I am not sure about non-M e46s

Edit: They have them as well

http://www.realoem.com/bmw/showparts.do?model=BN53&mospid=47713&btnr=41_1098&hg=41&fg=10

Nick325xiT 5spd
07-26-2005, 12:52 PM
Aren't E46 cooling ducts blocked? Or am I thinking about another car?
Doesn't really matter. The air doesn't really do anything useful without proper ducts.

dfmitch
08-01-2005, 08:02 PM
Unless you have measured the runout with a dial indicator, your rotors are probably not warped.
What you are experiencing, as I have, is variations in the the consistency of the pad/binder material deposited on the surface of the rotor during braking. These variations around the surface have different coefficients of friction, causing the pad's grip to fluctuate. Your stock pads are designed to grab the rotor surface cold or hot (not overheated), wet or dry. When you put a stock pad to use on a track with heavy brake use and the higher temperatures, the binder cooks out onto the pad surface (I'll wager you have a lot more brake dust from your pads after a track event than you had before). I recommend an intermediate pad (i.e., mid-way between street and competition) to solve the problem. I use Hawk HPS pads on my M3, followed tc kline's recomendations for bedding and have had no problems.
An alternative is to use a set of competition pads with their properly bedded rotors for track, and another set of OEM street pads and its set of properly bedded rotors for daily driving.

Do you think I can save my current stock rotors by switching to Hawk pads or will the pad/binder deposition never wear off and I need new rotors too?

jkuper
08-01-2005, 08:37 PM
http://www.newmantools.com/flexhone/fh4r.htm

SMOODY
08-03-2005, 11:13 AM
Just a couple of thoughts;

Do you guys think that getting the rotors turned would correct this problem?

What about taking a random orbit sander with some fine grit paper to them.

Either of these methods should remove any gunk on the rotor surface.

jkuper
08-03-2005, 11:20 AM
Just a couple of thoughts;

Do you guys think that getting the rotors turned would correct this problem?

What about taking a random orbit sander with some fine grit paper to them.

Either of these methods should remove any gunk on the rotor surface.

I don't think you are suppose to turn BMW rotors

I think 100 sand paper will remove deposits, it's basically what the flexhone tool is. In fact, Cobalt Friction suggests hitting your rotors with 100 grid sandpaper when switching to their pads to remove deposits from previous pads.

Pinecone
08-03-2005, 07:49 PM
The problem is, many times the pad deposits create a combo material with the rotor surfce, and this induces a difference in hardness. Which over time actually does create thickness variations due to uneven wear (reference Carroll Smith).

Sanding them or using a very abrasive pad may help.

I got the same think running stock pads at a DE in my E46 M3. Switching to Turner Cool Willy pads for track use, and Mintex red box for street, and lots of miles later, the jering went away.

wolfgang20878
08-04-2005, 10:55 AM
Check out Grassroots Motorsports, April 2005, on brake vibrations ("don't call it 'warped' "). As indicated above, the rotors develop uneven surface wear (the structure of the metal changes with heat plus some of the brake pad material, leading to varying hardness across the rotor) if you do not properly "bed" the pads/rotors when new. The article gives details on how to properly bed the pads/rotors, and what to do if you didn't and now have pulsation. If you can't find the issue I could fax it to you.

-John ('73 tii Turkis)

Barry
08-21-2005, 05:40 PM
I have a 2001 e46 330ci. I have driven it in three drivers schools and warped the rotors every time (once I was sharing the car with my son so I don't count that). I have stock BMW pads and rotors on. Does anyone have suggestions to avoid this- different pads, different rotors, brake cooling ducts? I don't think it's my driving. I have over 20 schools and have a 1988 325is that had original rotors for 150,000 miles and 15 schools. I also drive around the parking lot after the run to cool them off more. Has anybody had regular problems with e46 brakes on the track?


I had a 2001 330Ci, one of the first in the US, and I tracked it regulaarly. The OEM brakes simply are not up to the job for more than 5 or 6 hot laps. Then the heat build up is too much and they fade and rotors warp. I went to EvoSport slotted rotors and and upgraded brake pad, and that helped, but wasn't the solution. It just made things better.Hope that helps.
Barry

GStiles
09-06-2005, 03:01 PM
Following up on Wolfgang's post, here is a good article regarding "warped" brake rotors.

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

I was given this link by the guys at Road Race Technologies (RRT) after they just did some work on my brakes http://roadracetech.com. As you may already know, there is a parts swap meet at their location this Saturday.... and no, I do not work for them. :biggrin: