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02-07-2015, 07:19 AM | #1 |
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Shimmy while braking: deposits?
Working through my first month with the 07m coupe. 45k on the odometer. 700 miles of that is my doing. Daily driver for me. All stock brakes and pads (God the dust...)
The cpo I had done before purchase indicated that the brakes were still fine in relation to depth, etc. pads were at 10mm rear and 12mm front. I noticed last week that there's a slight shimmy under light braking when coming to a stop. It wasn't there (or I didn't notice it) prior to last week. I'm fairly certain I would have felt it. Was in the dealership yesterday for a full balance and alignment and of course the dealership immediately says warped rotors but it doesn't look like they did any analysis, just knee jerk reaction and greed. From reading through the forums it seems like it might be pad deposits and not rotor issues? I'm leaning that direction as well simply because: I haven't driven it hard at all. I've been washing it frequently (stupid stupid brake dust) It's been cold here in NC lately. Am I missing anything? Would some spirited driving and braking help to wear off deposits or is more intervention required (garnet paper and scrubbing) I'm already going to replace the pads because of the obscene levels of dust so if the rotors need to go as well I would rather do it in one shot. Just trying to see what additional troubleshooting I can do myself. Obviously a rotor runout would be the next step to confirm warping. Was just hoping there were some things I could do that wouldn't require pulling things off etc. |
02-07-2015, 10:58 AM | #2 |
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More testing: no shimmy on hard braking (50mph to 10) and it seems like it only gives a light shimmy on the first application of brakes.
For example: If I use the brakes to slow my speed, like when approaching a stop light. The first application of brakes gives a slight shimmy to the steering wheel. The next application, to come to a complete stop, doesn't result in the shimmy. Is this just because of the brakes warming up on first application and my unfamiliarity with the car? It's not severe by any means, and my brain is probably exaggerating it somewhat as well, but it is there. |
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02-07-2015, 12:13 PM | #3 |
M = Midlife Crisis
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The OE Pads will leave rust on the rotors after washing. If memory serves me, a few applications of the brakes bring things back to normal. I also recall feeling the sensation of the drilled rotors when braking from speed when I first got the car. I believe it's next to, or impossible to warp floating rotors. Buy a digital caliper device and measure the rotors to check if they're still in spec. Based on your mileage they may be close to done. I would personally recommend StopTech Street Performance pads as a replacement for the OE Pads. Very little dust and perform very well in most situations. Tire Rack has good pricing on the pads. Turner Motor Sports has deals on the OE Rotors from time to time.
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02-07-2015, 02:26 PM | #4 |
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Thanks for the sanity check. I'm think I'm leaning towards the r1 concept premier series drilled and slotted with ceramic pads. Have seen good comments on here and haven't seen anyone say anything bad about them.
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02-17-2015, 06:03 PM | #5 |
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Hi,
This Shimmy is due to your control arm bushings. At the first brake application they take their place (causing shimmy and a steering wheel movement) and at the second one, the shimmy is not here anymore till you continue driving few miles and start braking again. I experienced it and changed the bushings |
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02-17-2015, 06:58 PM | #6 | |
Midlife Crises Racing Silent but Deadly Class
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Quote:
From what you describe it is unlikely it's from brake deposit, but given the age of our cars, it is HIGHLY likely that it's from the front control arm bushings deflecting.
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02-18-2015, 02:27 PM | #7 |
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Thanks! Another part to replace
What's the best replacement? I see some notes about Rogue Engineering making an upgraded version but I don't see anything that calls out the Z4M version? |
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02-18-2015, 05:04 PM | #9 |
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I don't know if you can get them, but the Meyle HD do a great job.
I suggest to change them before changing any part on the brake system. It's cheap and 99% you won't need to buy other parts. |
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02-18-2015, 05:26 PM | #10 |
Second Lieutenant
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These?
I can't figure out if they are or aren't compatible with the z4m as it says both. http://store.bimmerworld.com/meyle-h...sets-p704.aspx |
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02-18-2015, 06:44 PM | #11 |
Midlife Crises Racing Silent but Deadly Class
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Those will likely "fit" but won't give you the increased caster angle that the offset bushings that came on the MZ4s will.
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02-19-2015, 06:55 AM | #13 |
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Yes, better to stick with OEM if there's a different caster angle on your Z4M. My Z4 is a 3.0SI.
Maybe for you the opportunity to change for a Powerflex solution. Last edited by babyfaby; 02-19-2015 at 07:09 AM.. |
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03-27-2015, 08:15 AM | #17 | |
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Quote:
FIXED! Thank you so much for the diagnoses. |
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08-10-2015, 10:36 PM | #19 |
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Excellent to hear your problem is resolved. I am having this issue also, time to swap the bushings.
Is oem best or will poly bushings give better results and wear? |
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09-08-2015, 08:22 AM | #21 |
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Glad we have such a great source of information for our cars on this amazing forum, keep it up everyone !
I have been through the same issue, and have actually gone down the road of "fixing a brake issue" only to have the shimmy still there, mine happens to be very intermittent, sometimes it will be smooth braking and other times it shakes quite badly. Will get FCABs done and will report back here after I get to test it out on the next track day.
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09-08-2015, 04:46 PM | #22 |
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I get a similar vibration vary intermittently. Most of the time it is fine. Once it was very bad in grid lock stop and go traffic and other times on a track with the brakes hot. I have replaced the FCAB abd RTAB with urethane from Pawerflex and had the alignment done. I haven't been to the track recently but it still happens occasionally on the street. Hmmmm? I have Bavauto slotted drilled rotors with cool carbon pads. Any thoughts?
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