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Discussion Starter · #1 ·
I have a 328i and I am wondering if anyone can help me. Every now and then I get the chance to accelerate up to about 100-120mph. This if fine exept that when i slow down, if I brake relatively hard (pedal halfway to end of travel) I notice a certain noise coming from the brakes. If you blow air out of your mouth and let your tongue vibrate to it, it kinda sounds like that. sorry but i dont really know how else to describe the sound. When I look at my rotors after the aforementioned braking, I see bluish streaks on the disks. Usually they are nice and circular which go around the whole disk. They wear away after a few days and braking performance is not lost. Is this bad? Is it normal? Any of you who track your M5's ever have this?
 

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I'm not sure, but it sounds like brake chatter. Usually two causes-1) glazed pads or 2) pads have worn enough that the length of travel required to engage is causing them to not be adequately supported by the housing. Just a guess.
 

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Zoli - just to cover all bases - the noise you describe is a bit like what the ABS sounds like when it engages. From the description of how hard you were braking, I doubt this is the culprit, but just wanted to be sure. If so, you would feel a vibration under your brake foot while you were hearing the noise....
 

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Discussion Starter · #4 ·
Thanks for the responces. I dont think it's the ABS, I've heard that before and it's not it. You think maybe my rotors are warped?
The main question I have is whether or not having the bluish streaking on the rotor bad? I showed my dad & he about freaked.
But no matter if I brake hard, I get blue, or If I brake not as hard, then its longer till I slow down & they still get blue. What am I to do? Thanks for how helpful you guys are. I really appreciate it.

[This message has been edited by Zoli 007 (edited 15 November 2000).]
 

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http://www.autoweb.lycos.com/garage/repairqa/ques007.htm

Excerpt:

"...if the rotor is warped or has hard spots (which are often discolored blue or black), the rotor should be resurfaced or replaced. Hard spots that develop from overheating or uneven tightening of lug nuts can create raised areas on the surface that often extend below the surface. The metallurgical changes in the rotor often cause the hard spots to return after a few thousand miles so replacing the rotor may be the best long-term fix."
 
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