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      08-13-2013, 10:41 AM   #1
sylonien
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Are my brakes ok? [2007 E92 M3]

Um not sure if its the same or not, but its brake related?

Stupid question, what's wrong with them? They don't feel they bite that well either, little spongy. And that's just from normal town driving. Feels like it doesn't stop very well at all. Not snappy or powerful.

You can feel the grooves and bumps if you touched them with your finger.
The worse are the rear ones and look like shit.

iDrive says 10-20k miles left. Is that the pads or discs?

And its a 2007 E92 M3 btw







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      08-13-2013, 10:53 AM   #2
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You aren't driving often enough, fast enough or braking hard enough.

Time for some new rotors.
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      08-13-2013, 10:56 AM   #3
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You serious?

Well they were like that when I got them.
I was driving fast sometimes and noticed how rubbish the brakes were.

Then I realized they didn't look right... was overwhelmed by my new M so didn't' really take in all the details. Or just ignored it and thought it would clear itself over time.

But hasn't even when I drive harder.

New discs and pads then???
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      08-13-2013, 01:45 PM   #4
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it seems like yr disc are all score ...my guess is you need to replace them asap !!!
mega bucks...or you might as well upgrade them to Ap Racing big brake kits
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      08-14-2013, 08:49 AM   #5
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man. No money for mega bucks.
I'm trying to find the price for oem / equiv. now and the cheapest bbk option? :P

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Last edited by sylonien; 08-14-2013 at 09:04 AM.
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      08-14-2013, 09:19 AM   #6
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Can you not get the discs skimmed as an interim improvement before new discs are required, especially with low mileage?

http://www.skimmydiscs.co.uk/
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      08-14-2013, 09:40 AM   #7
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Quote:
Originally Posted by Scottsard32 View Post
Can you not get the discs skimmed as an interim improvement before new discs are required, especially with low mileage?

http://www.skimmydiscs.co.uk/
No, there is no point skimming them; the main problem is not the uneven surface of the discs, rather, they have worn below minimum thickness, which means the compound has changed, and the structural integrity is now compromised - will be prone to severe cracking.

Sylonien, your pads are definitely above minimum thickness, and your brake wear sensor wires would not have been triggered, so all you really need to change are the discs and have the brake fluid checked. Saying that, think twice above ATE Superblue, as the blue tinge pretty much stays in your lines forever even if you flush it with other fluids in the future. I would personally recommend Castrol React Performance DOT 4 if you want a bit of an improvement over OEM for a similar price.

After you have changed your discs, and your pads and fluid are checked to be fine, do not expect brake performance (or pedal firmness) to return to normal immediately; it takes time for the surface of the old pads and the new discs to mate up perfectly, or you could accelerate the process by bedding the pads and discs in in a methodical manner.

Last edited by mlhj83; 08-14-2013 at 09:46 AM.
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      08-14-2013, 10:39 AM   #8
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I'm just worried that if I ran new rotors with these pads they would cause the same issue?

Cause wouldn't the pads have the opposite grooves on them now like the ones on the disc?
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      08-14-2013, 10:55 AM   #9
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Quote:
Originally Posted by sylonien View Post
I'm just worried that if I ran new rotors with these pads they would cause the same issue?

Cause wouldn't the pads have the opposite grooves on them now like the ones on the disc?
No, you wouldn't have the same issue after bedding-in. Yes, the pads will have uneven surfaces mirroring the old discs' surfaces, but the process of bedding-in will mate the surfaces up properly. Obviously, there is no harm in changing the pads as well, but given that your current pads have a decent amount of life left, why waste.

Even with new pads AND discs, you will encounter the same issue initially, as the surfaces will not be mated up properly, and the brake feel you will get, is very similar to what you are feeling now. The key is bedding the brakes in.

The past couple of performance cars I've gotten from new, have exhibited poor but adequate braking performance and pedal feel. Whenever I swap my road pads to my track pads, I also get poor performance and pedal feel. It's all down to bedding the brakes in and getting the opposing surfaces to mate up properly. If you had two bars of soap with uneven surfaces, and rubbed them together, eventually they'll both smooth out.

Obviously, if upon changing the discs, you find that the pad surfaces are very deeply grooved and pitted, then change them, as by the time the pads mate up properly to the new discs, the pads would have worn down significantly, where it would have been more cost effective to put new ones at the same time as changing the discs.

Last edited by mlhj83; 08-15-2013 at 11:34 AM.
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      08-14-2013, 11:14 AM   #10
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Here's a simple illustration of the cross-section of different pad and disc surfaces that can occur:
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      08-15-2013, 08:32 AM   #11
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That makes perfect sense.
Thanks for all that!

I'm shopping around for prices at the moment. The pads isn't that much more so probably worth doing it at the same time if I'm going to do this.
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