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      05-23-2011, 10:19 AM   #1
mhughett
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What is going on with my M brakes????

My car is on it's 4th or 5th set of brake rotors over the last 3.5 years and 18k miles. I bought the car last July at the dealer with 8k miles. It had a slight judder when braking from highway speeds when I bought it but I got new rotors put on last fall. It started to occur again and new rotors and pads were put on in March. Now it is at the dealer again for the same problem. Each time, the dealer tells me that the rotors are out of spec--the last time with runout of .0015" or more. The rotors look new or barely worn. I am very light on my brakes and most of my driving is expressway with little braking. In fact, my 2003 530i (also with manual transmission) still has the original pads and rotors and they still work perfectly with no vibrations at all. Is there anyone on this board that has had similar experience and can give some ideas as to what could be causing rotor runout and vibrations within 3 months or so with no hard driving? I've tried "bedding in" the brakes and this has had no effect. This is driving me crazy and the car is going to be out of warranty after this year. I certainly can't afford to replace rotors several times a year on my nickel.
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      05-23-2011, 11:12 AM   #2
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Had the same issue with my Z3. Good rotors last only short periods before warping. Ended up selling the car, but I think one of the hubs may be bad, causing anything but a perfect rotor to pulse the pedal. Possibility #2 is you are being too picky. A tiny bit of brake shudder is normal IMHO.
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      05-23-2011, 11:22 AM   #3
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Quote:
Originally Posted by Swanicyouth View Post
A tiny bit of brake shudder is normal IMHO.
Definitely disagree.
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      05-23-2011, 11:41 AM   #4
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Quote:
Originally Posted by MIKe86 View Post
Definitely disagree.
Trust me when I tell you that when I'm going along at 70mph on the highway and traffic comes quickly slows down in front of me, the shudder I feel is anything but "normal". What is really strange is that after the last change in rotors, it felt fine for about 5-6 weeks. Then all of a sudden in one day it started up again. It's not like a gradual deterioration. It's like it was not there one day and then it appeared the next day and has stayed ever since. As for the hub analysis, that might seem plausible if only one of the rotors was out of spec. However, the last time I got them changed, the ticket said both were out. I'm going to be more persistent with the dealer to find the cause this time and not just address the symptoms of the problem.
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      05-23-2011, 12:01 PM   #5
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I have no idea why this is happening, but on our cars we have no "judder" and that's after a few track days.

Just thinking out loud, some possibilities:

Hub, as noted by Swanic
Calipers--applying even pressure both sides?
Calipers--sticking?

Some of the above seem unlikely given we have floating rotors. I'll leave the definitive answers/ideas to folks here who are much more technically saavy than I.
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      05-23-2011, 12:04 PM   #6
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Mine has some shudder too, but it's not a real problem; safety is not impacted. The car doesn't veer off in another direction and it still stops when it has to. Inspection officials here do not care.

My dealer said the rotors could be replaced, but advised against doing so until they were more worn.
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      05-23-2011, 12:09 PM   #7
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Quote:
Originally Posted by Finnegan View Post
I have no idea why this is happening, but on our cars we have no "judder" and that's after a few track days.

Just thinking out loud, some possibilities:

Hub, as noted by Swanic
Calipers--applying even pressure both sides?
Calipers--sticking?

Some of the above seem unlikely given we have floating rotors. I'll leave the definitive answers/ideas to folks here who are much more technically saavy than I.
I'd vote for this cause as well.
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      05-23-2011, 12:38 PM   #8
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brake rotors warped

Hub, as noted by Swanic
Calipers--applying even pressure both sides?
Calipers--sticking?

That was my first thought also.
The calipers need to have a look.

Please report back with findings.
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      05-23-2011, 12:59 PM   #9
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Quote:
Originally Posted by Finnegan View Post
I have no idea why this is happening, but on our cars we have no "judder" and that's after a few track days.

Just thinking out loud, some possibilities:

Hub, as noted by Swanic
Calipers--applying even pressure both sides?
Calipers--sticking?

Some of the above seem unlikely given we have floating rotors. I'll leave the definitive answers/ideas to folks here who are much more technically saavy than I.
I took both sides apart last week looking for irregularities, including removing and cleaning both rotors and found nothing out of the ordinary. The caliper pins were lubed and there was no evidence of sticking. Given that the calipers float, it's unlikely to be a sticking problem if they move along the pins. I'll certainly let you know what they finally come back with. Since the technical rep will be involved and they can see the history of prior repairs, I hope he digs a little deeper this time.
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      05-23-2011, 03:23 PM   #10
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How quickly are you going through pads?
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      05-23-2011, 03:48 PM   #11
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The pads aren't wearing much at all and there doesn't seem to be a variance between inboard vs. outboard pad wear. The issue is strictly with the rotors.
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      05-23-2011, 04:07 PM   #12
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Quote:
Originally Posted by mhughett View Post
The caliper pins were lubed and there was no evidence of sticking. .
You don't lube the pins.
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      05-23-2011, 04:47 PM   #13
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Could this possibly be pad material buildup on the rotor, exhibiting the same symptoms as a warped rotor? Just a possibility..

If you have ruled out any caliper issues, and you think that the spindles are good, plus you state that you are really light on the brakes, pad material buildup is a possibility.

The reason I say this is that I get pad buildup and it starts a slight shuttering/vibration. The way I fix it is some really hard braking or rebedding the pads or another track event. My brakes are at there best for the first two weeks after a track event... then it starts.

In regards that the dealer says that they are warped, it could be that you have a good dealer, he just wants to fix the issue so they 'say' the rotors are warped and out of 'spec' so BMW will reimburse them for the repair. All things considered, this is a good thing, but yes, I agree that YOU want to know the root cause.
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      05-23-2011, 05:55 PM   #14
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As I stated above, I've tried "bedding in" the pads per the Zeckhausen website to remove irregular pad deposits. I've also done a day at the track. Neither has helped with the problem.

As for whether caliper lube should be put on the pins, I've heard both sides. BMW makes small packets that they say should be used for pins as well as contact points between the pads and calipers.
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      05-23-2011, 07:47 PM   #15
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Quote:
Originally Posted by mhughett View Post
As for whether caliper lube should be put on the pins, I've heard both sides. BMW makes small packets that they say should be used for pins as well as contact points between the pads and calipers.



http://www.bimmerfest.com/forums/sho...81#post6085481
.
.

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      05-23-2011, 07:55 PM   #16
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Is the seal on the caliper piston still intact or has it popped out of the caliper? If it has, then look for rust on the outside of the piston where it slides into the caliper body. Just another thing to check though if this is the case you would see uneven pad wear on the inboard/outboard pads.

Also, try to bed your brakes with DSC turned off and make sure you don't hit ABS.
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      05-23-2011, 08:00 PM   #17
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Not doubting you Ron. Your advice is usually spot-on. I'm just curious as to why not to use it. The information might prove useful at some point in my discussions with my dealer.
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      05-23-2011, 08:47 PM   #18
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Improper bedding...

Who beds your pads? What pads are they and what sort of use do they get?
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      05-23-2011, 09:02 PM   #19
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Quote:
Originally Posted by mhughett View Post
Not doubting you Ron. Your advice is usually spot-on. I'm just curious as to why not to use it. The information might prove useful at some point in my discussions with my dealer.
BMW thinks it works better without the grease. Maybe dirt with the grease makes it not slide as well. It does say do not grease for some reason.
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      05-23-2011, 09:05 PM   #20
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Quote:
Originally Posted by BTM View Post
Improper bedding...

Who beds your pads? What pads are they and what sort of use do they get?
I've bed-in the pads using instructions from Zeckhausen. As for the pads, they are OEM pads and get fairly light use.
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      05-23-2011, 09:13 PM   #21
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Quote:
Originally Posted by mhughett View Post
I've bed-in the pads using instructions from Zeckhausen. As for the pads, they are OEM pads and get fairly light use.
How are your rotors after the bedding? Do you do a second cycle? It really sounds like pad deposits to me...

Don't hold your car in place with the brakes after hard braking (could leave deposits)...if your rotors are truly warping, they have been installed improperly time and time again (did the dealer do this, did you?). Otherwise, sounds like pad deposits but if you truly aren't over working them...
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      05-23-2011, 09:21 PM   #22
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I think BTM might have the best candidate for the issue. If we've ruled out calipers, uneven pad wear, and hubs, and given the floating rotors, the only thing left is pad deposits. Occam's razor probably applies here.

I recall several folks having "judder" after track days (overheating the stock pads). And with proper bedding you really have to drive an extended period to cool down the brakes w/o re-engaging them of the whole exercise can get messed up. I'm not saying you're doing it wrong--rather I'm saying that when I bed the brakes the hardest thing is finding a stretch of road where I can do the bedding and then drive a good distance (at a decent speed) to cool down the brakes and not mess up my nice even deposit layer.

In terms of bedding/re-bedding, I'm not sure the stock pads have enough "bite" to actually clean off the deposits. Only a pretty aggressive pad will do this once deposits build up, and even then it might be necessary to use sandpaper on the rotors. At least that's what I recall from a discussion over on Planet-9 (the Cayman/Boxster boys were discussing this issue, and the type of pads factored into the mix as believe it or not sandpaper--again, assuming my memory is correct).

One of the "advanced" track guys (Lucid, Jmillet, Hack) may have more to add to this...

Last edited by Finnegan; 05-23-2011 at 09:26 PM..
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