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Suspension & Braking Forum by BimmerWorld
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Old 03-20-2013, 04:33 PM   #1
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Thumbs Up EXTREMELY useful article from Stoptech on mythical "warped brake rotors"

Everyone that owns a BMW and at some point will need to replace the brakes should read this:

http://www.stoptech.com/technical-su...nd-other-myths
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Old 03-20-2013, 04:44 PM   #2
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Old article, but still good. Been on their website for years.

One of their articles that doesn't apply to the E46 is the brake bias article, as this is electronically controlled by DSC so it doesn't matter what size brakes you have front to rear.
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Old 03-20-2013, 05:24 PM   #3
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Very odd, I have never worked for Shelby, but I have certainly come across warped rotors- I even watched while they turned them, and they were indeed warped as I could see and hear the lathe cutting the uneven surface....
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Old 03-20-2013, 05:28 PM   #4
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Very odd, I have never worked for Shelby, but I have certainly come across warped rotors- I even watched while they turned them, and they were indeed warped as I could see and hear the lathe cutting the uneven surface....
The article explains that...
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Old 03-20-2013, 08:56 PM   #5
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One of my rotors is definitely wobbling. I can hear the pad grabbing in one location when I spin it, and I have shimmy on braking. Still trying to investigate this.
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Old 03-20-2013, 09:40 PM   #6
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And I explained my experience watching several rotors being machined that were obviously warped.



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The article explains that...
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Old 03-20-2013, 09:46 PM   #7
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Old 03-20-2013, 10:00 PM   #8
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Runout is not synonymous with warpage. Did you even read the link?
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Old 03-20-2013, 10:45 PM   #9
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Did you watch the video?

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Runout is not synonymous with warpage. Did you even read the link?
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Old 03-20-2013, 11:04 PM   #10
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Quote:
Originally Posted by mkodama View Post
Old article, but still good. Been on their website for years.

One of their articles that doesn't apply to the E46 is the brake bias article, as this is electronically controlled by DSC so it doesn't matter what size brakes you have front to rear.
Hmmm I can lock up my rears...
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Old 03-21-2013, 12:54 AM   #11
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Hmmm I can lock up my rears...
As they should, right around the same time as the fronts, and right before ABS unlocks them.
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Old 03-21-2013, 12:58 AM   #12
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And I explained my experience watching several rotors being machined that were obviously warped.
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Did you watch the video?
I don't think you're understanding what was said in the article, if you read it. It explains that video, and what you think is warping.
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Old 03-21-2013, 01:09 AM   #13
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Did you watch the video?
I have my A5. I can and have turned rotors.

Interesting about the ABS unit being able to alter brake bias. I knew it was really sophisticated in the e46...do you have any more info about it mkodama? Or do you just mean that the ABS will counteract any hydraulic bias present?
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Old 03-21-2013, 02:17 AM   #14
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The following brake pads warning paragraph on that article is not applied to E46 either, because E46 uses 2 brake wear sensors mounted on the pads (one on front left and one on rear right) to monitor the pads wear instead of the floater mounted inside the brake fluid reservoir as the paragraph stated. When the brake pad wears down to the minimum thickness, the rotor contacts with the sensor and grinds away the wire loop resulting in opening an electrical circuit and a light appears on the dash warning the driver that the pads should be replaced.

In most modern passenger cars, the brake fluid reservoir is designed with a specific volume and is equipped with an internal float. The volume corresponds to the amount of fluid that will be displaced when the pads have worn to the point of replacement plus a generous reserve. When the replacement point is reached, the descending float completes an electrical circuit and a light appears on the dash warning the driver that the pads should be replaced.
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Old 03-21-2013, 07:43 AM   #15
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I did read every word of it, have an extensive background in machining, metallurgy and I think we are down to semantics here.



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I don't think you're understanding what was said in the article, if you read it. It explains that video, and what you think is warping.
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Old 03-21-2013, 07:44 AM   #16
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As they should, right around the same time as the fronts, and right before ABS unlocks them.
Nope, rear locks then unlocks then front locks...
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Old 03-21-2013, 01:32 PM   #17
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I did read every word of it, have an extensive background in machining, metallurgy and I think we are down to semantics here.
I still don't think you get it though, what you were seeing as clear "warpage" was most likely excessive pad material buildup in one particular spot that makes the rotor appear to be warped. Sure, machining them down so they are nice and smooth makes you think that you've refinished a previously warped rotor, when in reality all you did was machine down the excessive pad material that was transferred to the brake disc.

Don't you think that if the rotor was truly warped, the warping would go throughout the entire rotor, and not just be in one small spot? think about it...
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Old 03-21-2013, 01:35 PM   #18
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This video is a CLEAR demonstration of excessive pad material buildup on the brake disc. Just take a look at the inner veins of the rotor, they are spinning perfectly straight, so you're going to tell me that somehow or other, just the outer surface of a rotor warps and the warping does not continue through the entire rotor into the inner veins??? This is ridiculous and just proves every point being made in the article I presented..
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Old 03-21-2013, 01:40 PM   #19
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Sure man, whatever you say... That sound of metal being ground from both sides of the rotor is just brake pad material


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This video is a CLEAR demonstration of excessive pad material buildup on the brake disc. Just take a look at the inner veins of the rotor, they are spinning perfectly straight, so you're going to tell me that somehow or other, just the outer surface of a rotor warps and the warping does not continue through the entire rotor into the inner veins??? This is ridiculous and just proves every point being made in the article I presented..

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Old 03-21-2013, 01:42 PM   #20
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Did you even watch the video?

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Originally Posted by trizzuth View Post
This video is a CLEAR demonstration of excessive pad material buildup on the brake disc. Just take a look at the inner veins of the rotor, they are spinning perfectly straight, so you're going to tell me that somehow or other, just the outer surface of a rotor warps and the warping does not continue through the entire rotor into the inner veins??? This is ridiculous and just proves every point being made in the article I presented..
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