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Old 06-20-2017, 05:47 PM   #1
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Shakey brakey!

Just back from a 2 day event at Mont Tremblant, fantastic weather and a huge amount of fun! Car (2004 Boxster S) ran well with no problems except: brakes...
At my last event in May, I noticed that when my brakes gor hot, say after 3 or 4 laps, I would get major vibration through the steering wheel. The rotors were Meyles all around. I changed the front rotors for some Zimmermanns, after having cleaned and sanded the hubs. I then seasoned them acourding to Hoyle. I also installed the GT3 air ducts. I have received some new pads (EBC Yellowstuff) but didn't have time to bed them for this event so I ran with my Redstuff pads which still had lots of legs. Unfortunately, the shimmy persisted. I will be installing the Yellowstuff pads in the next day or so.
Is it possible/usual for a brake pad to cause this juddering problem?
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Old 06-21-2017, 04:16 AM   #2
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haven't heard that being caused by pads but I guess if they overheat anything is possible. Redstuff really aren't track pads.

Could it be your lower control arm bushings?
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Old 06-21-2017, 04:46 AM   #3
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My Toyota FJ shimmies when I brake from highway speed sometimes. Tire Kingdom turned the rotors and it went away a little but still comes and goes. 150K miles, I haven't checked into any of the suspension. I've never had this on my Boxster but I have done some tracking with EBC RedStuff (14'ish track days? Two sets of fronts/one set of backs) and never had this. Maybe worn out ball joints or rubber in the front suspension? I have replaced all my parts (except front tie rods) so if it is from that, maybe that's why I never felt it?
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Old 06-21-2017, 05:03 AM   #4
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It's really only at the track and really only when the brakes get really hot, after a number of laps. Soon as they cool down, smooth as silk. Odd.
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Old 06-21-2017, 05:21 AM   #5
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I'm having the same issue with my car at the track. New Meyle rotors and Redstuff pads. The suspension is all new. It's discouraging to hear that you tried Zimmerman rotors and are still having the same issue.

The first time at the track, the car had the rotors that were on it when I got the car, which probably weren't the original rotors (145 K), and it never warped the rotors. It did fade the brakes badly, though. At that time I had the Greenstuff pads. The rotors were pretty worn, so I got new ones and the Redstuff pads. Now no fade as far as a I can tell, because the rotors warp so badly that you can't brake hard after a few laps.
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Old 06-21-2017, 05:48 AM   #6
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It's strange that you are only getting the vibration with hot brakes, if it was pad deposition, it would be there at all times. Are you sure that you are not confusing hot brakes with pushing the car hard? Have you checked wheel bearings? Are you getting any brake pad knock back?
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Old 06-21-2017, 05:49 AM   #7
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Now no fade as far as a I can tell, because the rotors warp so badly that you can't brake hard after a few laps.
See -Warped- Brake Disc and Other Myths
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Old 06-21-2017, 06:30 AM   #8
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A cracked rotor will vibrate under thermal stress. Also true for improperly mixed cast iron (impurities).

A warped rotor will vibrate no matter hot or cold. Permanent stage.

Go easy on them until you find the cause
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Old 06-21-2017, 06:54 AM   #9
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I don't think the rotors are warped or defective since the problem is identical even after changing disks. The braking holds up well with little fade, it's just the shaking in the steering wheel that is bugging me.
I'm going to bed these new EBC Yellowstuff pads and see what happens at the next event in July. I'll report back here.
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Old 06-21-2017, 07:31 AM   #10
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I don't think the rotors are warped or defective since the problem is identical even after changing disks.
Pads does not cause vibrations - to my knowledge mind you. Unevenly wear rotors does (warped).

How much sanding have you've done on the hub? If you've removed material on those hubs, then they are now out of tolerance. Best just to clean those things with a brush. You can check your hub run-out with a new rotor installed and a magnetic dial indicator held on the caliper. Run-out shouldn't exceed 0.05mm for a 'performance' set-up. Just asking this because 0.05mm is pretty easy to achieve with #100 grit sandpaper.

But I'm sure you wouldn't have done that anyway. You can also check for rotor wear/warping using the same dial-indicator technique.
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Old 06-21-2017, 07:53 AM   #11
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The rotors aren't cracked, they are new. I used to race a first generation RX7 that would destroy rotors in one race weekend. During the race, they would crack, so I know what that feels like.

I properly bedded in the pads to the new rotors. It's tempting to say that I've bedded in brakes hundreds of times during my racing career, but realistically, I've bedded in new brakes at least 75 times. I know the procedure, and I've read the EBC directions. The rotors are a uniform color around the discs, so I don't see that I've created any hot spots during the bedding process.

As I mentioned above, the RX7 that I raced taught me all the tricks to extending the life of brakes, like staying off of them completely on the cool-down lap, moving the car forwards and backwards every few minutes once the car is parked to keep the pads from heat-soaking the discs, and so on. That car was inherently under-braked, so I had to learn to not only manage the brakes during a race, but also manage them when the car wasn't on the track. In other words, I know what I'm doing with brakes.

It's not pad knock-off. I also raced a car that had that issue (Datsun 1200), so I'm familiar with that as well.

Once the brakes cool off, there is no vibration. They are fine on the street. The problem is only there when the brakes get really hot.
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Old 06-21-2017, 09:10 AM   #12
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Interesting that Racerboy and I seem to have the identical problem and the common denominator seems to be the Redstuff pads. Even after changing rotors and rebedding, the problem persists. I have a brand new set of Yellowstuff pads not yet installed but now I'm wondering whether I shouldn't have gone to Pagids
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Old 06-21-2017, 10:14 AM   #13
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Even after changing rotors and rebedding, the problem persists.
Assuming you and Racerboy have brand new and performing brake fluid in there? Boiling fluid not only cause fade, it also create 'random' energy distribution on the pads & rotors. Vibration and/or warping can occur.

When brake/vibration issues occurs in the pits here, the first thing the boys does is checking mechanical run-out, flushing out the fluid and slamming in new rotors. Pads is the last thing on their list (I think). They normally link pads/compounds to breaking performance, not vibrations.

Annoying bug you guys got there :/ Hope you sort it out... can't imagine what it feels like coming in a hairpin at speed with a compromised breaking system. I'd pee myself I think

glwf
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Old 06-21-2017, 10:49 AM   #14
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Fresh fluid in my car. The pedal is nice and firm. That is unlikely to cause the symptom NewArt and I are experiencing.
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Old 06-21-2017, 10:59 AM   #15
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Fresh fluid in my car. The pedal is nice and firm. That is unlikely to cause the symptom NewArt and I are experiencing.
Ditto! Motul racing fluid.
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Old 06-21-2017, 11:17 AM   #16
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The only bedding I did on my EBC yellows was a 250 mile highway drive to summit point.
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Old 06-21-2017, 11:19 AM   #17
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whatever it is, seized piston(s), torn bushing, wiggling joints in drive train, that will need to be taken care before buying a new consumables. Once the vibration sets, that rotor is shot and it sucks I heard a few times loll

Would be hard and unfair to conclude that the pads are the culprits tough, apretty large community would report the same issue if they were prone to vibration. Just never heard about this, fascinating subject that's why I've joined

New Pads technology perhaps? some super sticky hardened alloy, possibly from recycled cars parts?
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Old 06-21-2017, 11:37 AM   #18
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It's really only at the track and really only when the brakes get really hot, after a number of laps. Soon as they cool down, smooth as silk. Odd.
missed that part loll

Old car man, drive safely. Looks like fatigue of the entire system, old calipers and all. Change all situation almost

Keep its last 100k for the road only

out
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Old 06-21-2017, 05:03 PM   #19
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missed that part loll

Old car man, drive safely. Looks like fatigue of the entire system, old calipers and all. Change all situation almost

Keep its last 100k for the road only

out
Naw, I'm not buying that.
I WILL find the solution!
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Old 06-21-2017, 06:23 PM   #20
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That's funny!!!
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