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05-06-2017, 01:26 PM | #1 |
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Brake vibration
During my first track day at the ring in my car this past weekend, I noticed the steering wheel would shake during braking. This was a little surprising being that I've never had any vibration at all but this was the cars first track day ever. I finished the lap and exited the track (I didn't want to hot lap the car back to back even thought I felt it wouldn't issue.) Afterwards the car and brakes cooled after grabbing lunch and I went back out for another lap. I was surprised again that the brakes felt normal for the first 2-3 braking zones. Afterwards the wheel started to shake just like before. I have a set of front and rear track pads with the factory rotors. I can't remember the brand but the fronts are yellow and the rears are black.
I'm no stranger to brake vibrations but in my experiences the symptoms of warped rotors don't go away once the brakes cool off. Any advice short of simply replacing the rotors? The car has 29xxx miles with no track days up until present. I plan to resurface them but not sure if it will happen again when I return to the ring in a month or two. Update: The brake I used at the track were pagid rs. Last edited by Logodude; 05-07-2017 at 12:27 PM.. Reason: Add infor |
05-06-2017, 06:01 PM | #2 |
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Usually you will get shaking over a certain speed . I'm guessing your first few turns are not as fast as the last few? Anyways this sounds like brake of deposits to me . I used hawk blue 9012 to clean my rotors and they were vibration free after that.
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05-07-2017, 03:22 AM | #3 |
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So the vents might be blocked? I guess that would seem obvious but just didn't think of it.
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05-07-2017, 09:05 AM | #4 | |
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Sounds like you have some uneven pad deposits on the rotor surface. I would suggest trying to re-bed/re-burnish the pads: https://www.zeckhausen.com/catalog/i...Path=6446_6443
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05-07-2017, 12:28 PM | #5 | |
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05-07-2017, 12:31 PM | #6 |
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Tried to resurface the rotors today when I switched out the pads back to OEM's and they said the machine doesn't go big enough for even the rear rotors. So I'll have to search around to find another place to resurface them. I shined a light through the vents didn't see any blockage through the holes.
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05-07-2017, 12:37 PM | #7 |
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This is why it's easier to buy the hawk blue 9012 pads and run them to clean the rotors. They are so abrasive they will take off ~0.3mm of rotor thickness after a session of hard stops.
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05-07-2017, 12:57 PM | #8 | |
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No. The point of bedding is not to remove material, but rather, to deposit a very thin layer evenly across the entire swept area. If that doesn't work, you might need to do something abrasive such as a Flex-Hone attachment on a drill: https://www.amazon.com/dp/B007INTE3Q...ZBU1088Q&psc=1 When I talked to Dave Zeckhausen (owner of the above site), he said this would be the next step he would take if re-bedding doesn't work.
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05-07-2017, 05:09 PM | #9 |
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Funny - this is very relevant for me this week/last week.
I was driving to The Ring, still in the UK, and gentle braking from about 65mph to 50mph suddenly set off some mild vibration. I have never had any problems with these brakes (or the brakes on previous M3s) before now. The disks are original, and so are the pads (34000 miles) and I am very easy on my brakes, so was surprised to get this. Also I followed the recommended bedding in process when new (proper heat cycling, not just gentle braking for the first 250 miles or whatever). Later in the day, while enjoying the freedom of the autobahn, I had to brake from 140mph when a lorry decided to change lanes without looking/caring. Then the vibration was much worse, and definitely took the fun out of autobahn time. When I got back to the UK I jacked up the car, and spun the front left wheel (where I sensed the problem was) and as well as getting a slight inconsistency in the pad/disc noise, I also detected a distinct tapping from the disc, once per revolution. Visually, there was minimal disc wear. To the dealers.....who measured thickness (above minimum thickness) and run-out, which was 0.3mm on the outside surface and 0.2mm on the inside surface. Not sure how you can have different numbers for inside versus outside as this suggests a change in thickness as well as warping/shape... BMW rejected my out of warranty claim, ignoring the fact that the disc is still above minimum thickness and I have 12mm of unused pad left - after 34000 miles that says I do not beat my brakes. £986 lifted from my wallet, for 2 disks and 4 pads, plus fitting. Snottagram being composed now.... |
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05-08-2017, 02:53 AM | #10 | |
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05-08-2017, 08:57 PM | #11 |
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The OEM rotors are not usually ones to warp...They are very capable rotors. Vibrations in the steering under braking from high speeds are usually caused by uneven pad deposits.
I just went through the process to remedy this on an '11 M3 using Hawk blue pads to strip the old deposits. I was going to post a DIY on the issue as soon as I get some time. |
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05-08-2017, 09:42 PM | #12 |
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Just curious but after you have a high speed run, do you cool your brakes down with some cruising and not come to a complete stop for a good amount of time?
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05-09-2017, 04:11 AM | #13 |
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Once I go through the final corner I get out of the racing line and cruise about 60-80mph and exit the track and proceed to the parking area. So probably about 5-10 minutes with traffic once I exit the track. But it's stop and go in the traffic.
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05-12-2017, 03:06 PM | #14 |
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I decided today to go out with the factory pads and do some "spirited driving" to heat up the brakes to try and replicate the same issue but with the factory brake pads.
I was unable to replicate the issue. So either the factory pads don't get as hot (I know I wasn't on a track but I got them hot enough they started to squeal) Or I need to sand the track pads (they were used when I went to the track) and re-bed them in. Any thoughts? |
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05-12-2017, 03:18 PM | #15 | |
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Do not sand your pads down. You will contaminate them. If the pads were uneven, either they were defective from the manufacturer or a brake component was bent/broken/stuck.
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05-12-2017, 03:52 PM | #16 |
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Being the pads were used, they might have been contaminated already. There weren't any issues with the brakes when I changed the pads. The OEM pads don't have the same issue.
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05-12-2017, 04:57 PM | #17 |
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As others have said, this is most likely the result of pad deposits - both OEM and Pagids are prone to this. I hate to result to the Search response, but this forum has several threads re: this phenomenon. It's extremely unlikely that your rotors are warped. These pad deposits will wear off over time, but it could take over 100 miles of non-track driving.
Next time you go to the track, use different track pads or follow the bed-in procedure specific to the Pagid pad - it's quite different and specific than other pad procedures. You can find it on the Pagid site if needed.
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05-13-2017, 01:45 PM | #19 |
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05-13-2017, 03:49 PM | #20 |
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If I drove 300 miles to the track, do you think they should have been bedded in before I got there. I did do 4-5 medium stops immediately after installing them but nothing to hard and made the trip to the track the following weekend.
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05-13-2017, 03:59 PM | #21 |
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To bed the brakes I usually make 6-8 slowdowns from 60-5 mph applying as much pressure as needed to almost kick in ABS but without coming to a complete stop. You will certainly smell the brakes and they will usually smoke a bit too. A few medium stops probably won't bed adequate to bed in most pad types.
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