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Discussion Starter #1 (Edited)
Brake parts:
  • ECS Slotted Rotors
  • Stoptech Street pads
  • New brake pistons
  • New guide pins and bushings
  • New piston O-rings
Recently completed work applicable to this issue:
  • New Thrust arms
  • New Center steering linkage
  • New Idler arm and bushing
  • New Tie rods
- Front straight control arms (wishbones) and sway bar links remain un-replaced, both likely worn
- Rear control arms and bushings haven't been replaced and are likely worn
(shaking is from front of car)
__

I just recently rebuilt my front brake calipers due to an issue I was having with one. The inside (piston side) pad stuck to the rotor wearing it's inner face and the pad down to bare metal, while the rest of the brakes and the other side of the rotor was wearing identically to the passenger side front brakes which had no wear issues.

I decided to do a full caliper rebuild on both front calipers to alleviate the issue and have fresh calipers.
I installed new caliper pistons, o-rings, guide pins, and bushings. I made sure to clean the cylinder extensively before inserting the new piston and only lubed it with brake fluid. The pistons on both sides went in easy though didn't seem to push in as far as they should, they got as far as just before flush with the caliper compared with the OEM untouched caliper. We we're able to get it assembled but the pads were a tight fit and we figured we made a mistake bleeding the brakes (we did). Took the car for a drive and pedal fell to the floor and was slow coming back up. Only braking would occur 3/4 inch from the ground, and oddly it would often actuate ABS with little braking force when the pedal is pressed as far to the ground as possible. Definitely got air in the system.

The next day I bled the 2 front brakes and the braking now seems perfect and the car's drivable; pedal is firm and modulation is smooth and accurate, much better than it was before. I'm planning on doing a full ABS DIS flush when I install rear brakes, parking brake shoes, and new lines, this was enough to expel the air we accidentally got in the front lines.

However I've been noticing shaking anytime I hit the brakes above 40mph. Sometimes the shaking is a bit violent but eases away quickly into a vibration. Applying more pressure seems to help significantly in reducing shaking when hitting the brakes above 40mph, though I haven't tried that at speeds higher than 70mph and the car still slows down quick! Shaking wasn't totally eliminated though, just greatly reduced. (I torque my wheels carefully to avoid rotor warpage, I also cleaned the rotor's contact areas with the hub and wheels to ensure and perfectly even fitment.)

The pads have only been bedding to the rotor for about 20 miles, the first 5 miles being before they were properly bled with air in front lines which could have caused uneven distribution of pad material on the rotor, maybe this could be causing the shaking while braking? Could this go away after bedding in the brakes properly over more like 500 miles?

I'm not certain what could be causing this. The sometimes violent shake that eases away quickly just at the beginning of braking above at highway speed is concerning but is also rare and seems to depend on speed though I've yet to drive it enough to be sure.

Though I noticed nothing like this at all before the brake work, I'm considering my front straight control arms, I was planning Turner upgraded mononball straight control arms at some point and wasn't totally sold on them yet. I just don't want to throw money at that and still be left with this issue when the arms seemed to cause no noticeable issues before the brake work. And the jump from no shaking to this amount of front end shaking after just brake work is concerning to say the least!

Does anyone have any ideas? I'd appreciate your help!
 

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How many miles on it? Are you feeling it in the steering wheel with a “head shake” or shuddering of the steering wheel? That most likely would be a lower control arm issue. But it doesn’t show up as an instant violent shaking. Comes on with wear. Both of my E39s did this.. if it makes more of a vibration felt up front might be a possible warped rotor? I fought one for awhile. A dial indicator finally told the truth that a rotor was bad out of the box.
 

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Discussion Starter #3
How many miles on it? Are you feeling it in the steering wheel with a “head shake” or shuddering of the steering wheel? That most likely would be a lower control arm issue. But it doesn’t show up as an instant violent shaking. Comes on with wear. Both of my E39s did this.. if it makes more of a vibration felt up front might be a possible warped rotor? I fought one for awhile. A dial indicator finally told the truth that a rotor was bad out of the box.
The car has about 107k miles.
The shaking I feel through the steering wheel and front end of the car any time I hit the brakes at highway speeds. I doubt my control arms are the culprit just because they never exhibited any issues prior to the brake job, but it’s possible. A warped rotor out if the box is also possible, I may have that checked if there are no other possible solutions.
 

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When was the last time you balanced your wheels?
 

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107k miles?? - your looking at lower control arm issues soon for sure...
Just the nature of the E39s. Both of mine started nearing 100k. Saw it while braking above 60mph. Even if I lightly braked it would shake. It got to be violent on my first one. It seemed certain pavement areas would set it off more than others. Did you have slotted rotors before? More effective Braking so maybe adding more twisting moments to the LCA bushings?? Just thoughts here...
 

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Thrust arm bushings are usual culprit, but you have replaced those, correct? If yes you can rule those out.

When you say “pads have been bedding to the rotor” does this mean you did not actually bed the brakes? This doesn’t happen over a period of miles, it’s a procedure you do and then it is done. Read this for procedure and follow the link in first paragraph as to why. Driving and using the brakes will not evenly distribute a uniform layer of pad material on the rotor. Uneven deposits will cause vibration.


If you did actually bed in the brakes, I would replace the front controll arms (have them checked if out of spec replace). Worn swaybar links won’t cause a shimmy under breaking; with suspension evenly loaded left to right there is no force being applied to them, swaybars handle lateral loads, and have nothing to do with locating the hub assembly. I am not saying if they are worn and out of spec you shouldn’t replace them, just that they won’t cause a shimmy.
 

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Discussion Starter #7
107k miles?? - your looking at lower control arm issues soon for sure...
Just the nature of the E39s. Both of mine started nearing 100k. Saw it while braking above 60mph. Even if I lightly braked it would shake. It got to be violent on my first one. It seemed certain pavement areas would set it off more than others. Did you have slotted rotors before? More effective Braking so maybe adding more twisting moments to the LCA bushings?? Just thoughts here...
I had solid OEM rotors before. Is the "lower control arm" you refer to the thrust arm or straight control arm? The thrust arms were replaced around January of this year so they're definitely good. I was planning on replacing the other, straight control arms soon just to keep the suspension as tight as possible but if they were that badly worn to cause shaking I should've at least noticed something, anything before doing this brake job though I noticed nothing at all, even under hard braking from high speed, no shake or wobble whatsoever. I didn't even experience any shaking before I replaced my thrust arms!

Maybe you're right that braking performance is improved now and that may bring out some issue that was already there, but I didn't notice a hint of that issue before the brake job. My brake pedal is firmer and my Stoptech pads do have better bite then before.

Thrust arm bushings are usual culprit, but you have replaced those, correct? If yes you can rule those out.

When you say “pads have been bedding to the rotor” does this mean you did not actually bed the brakes? This doesn’t happen over a period of miles, it’s a procedure you do and then it is done. Read this for procedure and follow the link in first paragraph as to why. Driving and using the brakes will not evenly distribute a uniform layer of pad material on the rotor. Uneven deposits will cause vibration.


If you did actually bed in the brakes, I would replace the front controll arms (have them checked if out of spec replace). Worn swaybar links won’t cause a shimmy under breaking; with suspension evenly loaded left to right there is no force being applied to them, swaybars handle lateral loads, and have nothing to do with locating the hub assembly. I am not saying if they are worn and out of spec you shouldn’t replace them, just that they won’t cause a shimmy.
When I say "pads been bedding to rotor" I meant just the amount of miles on the pads and rotors. I haven't gone through the bedding procedure, I just tried this morning though! When braking hard or gently from 60mph I get varying degrees of shaking so decided not to keep trying and I don't really feel comfortable braking hard repeatedly if they keep shaking like this, it feels like something's eventually gonna break.

When the brakes were cold this morning and I tried braking from 45mph the shaking was BAD... felt like the front end was about to fall apart, the shifter was shaking as well which means the shaking is strong enough to affect the driveline 😳 Then the brakes warmed up a bit and it felt like the shaking was reduced. So I kept driving on the highway to keep testing the issue and found heat doesn't have much an impact on shaking, if any.

Car still runs up to 100mph fine and feels solid, oddly braking from 100mph produced almost no shaking whatsoever, maybe just a very slight vibration which could be mistaken for wheels which are very slightly unbalanced. 1 minute later from slower speeds around 70mph the shaking was back anytime I hit the brakes and got even worse as I took the off ramp and started braking from 50mph, violent shake for half a second then eased into a more consistent and less severe vibration until the car got under 30ish when the shaking stopped, I recorded a short video of this shaking before and on the off ramp and will upload it to Youtube and post the video here. You'll be able to see the steering wheel shake, how it's sometimes severe at first then gets better.

Braking from 40-80mph seems to cause the shaking intermittently with varying temperatures having little impact on severity.

Conclusions I can make so far:
  • Shaking seems to happen severely between about 40-80mph, but I can't be sure it won't happen at higher speeds
  • Shaking seems to vary with brake pressure applied but there's usually some shaking on initial bite regardless
  • Shaking is intermittent and barely seems to have any correlation with brake temperature
  • Sometimes I can stop from highway speeds between 40-80 with no shaking at all, only a slight vibration if that
  • Rotors' surfaces look like they're wearing evenly with no odd wear marks correlated to rotor/pad interface issues
  • No shaking whatsoever under about 40mph regardless of brake pressure
  • I don't feel any shaking feedback from brake pedal, just the steering wheel and rest of the front end of the car
  • Nothing feels unusual below 40mph, brakes feel perfect!
 

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Discussion Starter #8

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I am not saying the rotors are the issue- but you wouldn’t be able to see uneven deposits with your eye. Also when the brakes are new you must bed them in, no exceptions. Bedding in after deposits have formed is too late.

Something is loose or out of spec. Check that no calipers are sticking, (they can be intermittent but typically get worse with heat), have the rotors checked for runout, and have the entire front suspension checked for play. Anything out of spec correct it.

The thrust arm (called traction strut by bmw) #5 is the usual culprit. You should probably look at the control arm (aka wishbone) as well.

 

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All that you are describing points to a suspension or a steering/linkage issue.
 

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I’ll second my suspicions that it’s suspension - you described exactly what I’ve had on my 2 E39s, fixed with a rebuild of my control arms.. do a simple dial indicator check on the rotors to rule the rotor problem out, I’m a mechanic and never had what has been mentioned during the “bed” in process.
 

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Even if you didn't properly bed the brakes (I have done it both gentle driving, progressively harder for 50-100 miles or the Zeckhausen stomp on the brakes method), vibration shouldn't be that severe. In normal street driving, you are not going to leave that much in the way of deposits on the car, with one exception: when warm to hot and you pull up the handbrake. That is when you get uneven pad deposits that are noticeable.

Assuming your rotors are true and mounted correctly (no rust, sitting flush), the cheap way to clean the rotors is to put on a good set of race pads! At street temperatures, they will be very abrasive with the effect of truing up your rotors. Don't bed them in, you want them to be abrasive. If that cures the problem put in some fresh street pads and bed.

Having said all of that, I don't think it is brakes. It is thrust arm bushings. One important thing when replacing is they have to be tightened loaded. In other words, if they are tightened while the suspension is unloaded, they will wear out quickly, even though new. So talk to whoever did the install.

Personally, I have used the X5 bushings and have never had an issue. If you use those, they must be installed with keyway 180 degrees out from the stock M5 bushings. Long story, if interested, check very old thread "Crevier sucks".

Regards,
Jerry
 

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Agree with Jerry on thrust arm bushings...if the car wasn't at normal ride height when they were torqued, they can be toast in very short order. I've even seen some aftermarket (but supposedly "OE" supplier) thrust arms start leaking after a couple hundred miles on an E39 (they're filled with oil), and they were properly installed and torqued.

On the steering part replacements...ensure that the new (?) center track rod was installed correctly (there's a board post ages ago where someone installed it upside down!), and also ensure you have a new idler arm bushing too.

Re brakes...this it totally off the wall, but the worst experience I ever had with brake pads in over 40 years of DIY brake jobs was with Stoptech street pads on my E46 way back when they first came out around 2008-9 or so. I had severe shaking issues show up a short while after installing them with new rotors and bedding them in per Zeck procedure. It didn't make sense to me since these had only seen basic street duty, perhaps 300 miles, and I'd never had pad issue like that before. I tried multiple additional bedding sessions with minor success but in the end there were pad deposits that even my PFC01 race pads couldn't clean off (cementite). I bought another set of new rotors and switched to Centric ceramic pads and never had a further issue with that car's brakes ever again.

Find a small incline. Put the car at the top, windows down, in neutral, and let it roll very slowly...only a few mph, no more than walking speed. Very gently apply brake pressure -- just enough to have pad-rotor contact. Listen carefully for cyclic noise (i.e. if you have contact and then none). Allow the car to speed up to maybe 10mph, now do the same thing and tune into the the feel of the braking once again looking for cyclic response. Often if it's a pad deposit issue, these two tests will allow you to hear and then feel it. You can also try this from a slightly higher speed (~20mph) braking down to zero...hold a constant brake pedal pressure, gentle pressure but enough to stop the car eventually, and evaluate and pulsing as speed falls below 15mph or so.
 
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Discussion Starter #15
I use these purple numbers, [#1], to number a point I highlight in bold in your posts to make my reply to each point more clear.

Agree with Jerry on thrust arm bushings... [#1] - if the car wasn't at normal ride height when they were torqued, they can be toast in very short order. I've even seen some aftermarket (but supposedly "OE" supplier) thrust arms start leaking after a couple hundred miles on an E39 (they're filled with oil), and they were properly installed and torqued.

On the steering part replacements... [#2] - ensure that the new (?) center track rod was installed correctly (there's a board post ages ago where someone installed it upside down!), and also ensure you have a new idler arm bushing too.

Re brakes...this it totally off the wall, but the worst experience I ever had with brake pads in over 40 years of DIY brake jobs was with [#3] - Stoptech street pads on my E46 way back when they first came out around 2008-9 or so. I had severe shaking issues show up a short while after installing them with new rotors and bedding them in per Zeck procedure. It didn't make sense to me since these had only seen basic street duty, perhaps 300 miles, and I'd never had pad issue like that before. I tried multiple additional bedding sessions with minor success but in the end there were pad deposits that even my PFC01 race pads couldn't clean off (cementite). I bought another set of new rotors and switched to Centric ceramic pads and never had a further issue with that car's brakes ever again.
[#1} I don't think it is brakes. It is thrust arm bushings. One important thing when replacing is they have to be tightened loaded. In other words, if they are tightened while the suspension is unloaded, they will wear out quickly, even though new. So talk to whoever did the install.

[#1] I drove to @ChrisSKillaZ garage and he replaced the thrust arms for me in January, he's done the job multiple times and is an expert working on E39 M5s, knows these cars in and out. So I know he loaded the suspension and torqued everything down correctly so if the issue is suspension or control arm/bushing related it must be the straight control arms (wishbones) I've yet to replace.

[#2] I installed the new steering track rod myself and actually almost put it in upside down the first time 😂😂 fortunately I quickly figured that out and flipped it around to install correctly.
And yup I did install a new Idler Arm w/ bushing as well, I figured I'd change as many 20 year old rubber parts as I have access to for the freshest and tightest suspension possible. Once the front is fully sorted Im gonna do the same in the rear, everything's getting replaced, rear control arms, guide links, integral links, ball joints, and rear sway links.


[#3] I wonder if this could be a possible cause for the issue I'm having considering I'm using the exact same Stoptech Street Pads 🤔🤔Maybe it was just an issue with an early production run of these pads that's been sorted by now? Or a problem that recurs under certain circumstances...

I'll be testing the rotors with my new dial indicator gauge so hopefully that'll give me some insight, though I'm not sure how I'd be able to differentiate between rotor warpage and pad deposits since I'm assuming both would show as a similar discrepancy in rotor runout when measured with a dial gauge as I rotate the rotor.
Any ideas on how to tell if I'm measuring pad deposits or rotor warpage? I'll be testing the rotor runout later on today.



Something is loose or out of spec. Check that no calipers are sticking, (they can be intermittent but typically get worse with heat), have the rotors checked for runout, and have the entire front suspension checked for play. Anything out of spec correct it.
All that you are describing points to a suspension or a steering/linkage issue.
I’ll second my suspicions that it’s suspension - you described exactly what I’ve had on my 2 E39s, fixed with a rebuild of my control arms.. do a simple dial indicator check on the rotors to rule the rotor problem out, I’m a mechanic and never had what has been mentioned during the “bed” in process.
Thanks for your help and guidance guys, I appreciate it.

I ended up ordering a dial Indicator gauge and will be checking my rotors for warping/uneven deposits today. If my rotors are in good shape I'll know my suspension is the culprit and I'll order new front wishbones and front sway bar links for good measure, at that point every piece of rubber in the front suspension and steering will be new and fresh.

As stated above I don't know how to differentiate between rotor warpage and uneven pad deposits when measuring the rotors runout with a dial gauge, I'm assuming both defects would show up as the same rotor runout discrepancy when measuring the rotor, Any ideas on how to tell whether I'm measuring pad deposits or rotor warpage? I'll be measuring the rotors' runout later on today.

Thanks again
 

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You don’t have a warped rotor, as technically that doesn’t really happen- it’s a phrase used to describe lateral runout. You may have lateral runout caused by uneven deposits, lateral runout at the hub or bearing, lateral runout caused by poor manufacturing (uneven surface out of the box).

Or you may have a hot spot, where one area of the rotor has become overheated and has therefore changed in composition, it will become harder with a higher coefficient of friction on that spot- obviously that will cause shudder as the harder spot goes past the pad, the rest of the rotor also wears away more quickly, so now you have a hard “bump” on the rotor surface.

Lateral runout can be measured, hot spot will look like a dark stain on the surface.

I believe the temp at which cast iron starts to become malleable is around 1400f. Formula 1 cars will see 1200f on their brakes for brief periods. Given a road car will see much less, it’s highly unlikely you will ever get them hot enough to deform.
 

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he replaced the thrust arms for me in January
Inspect the rubber very closely and look for any sign oil might have leaked. There were some early batches that the oil leaked out within the first month or two of service, so pockets for dirt where it should not be and when you wipe it off it sticks to itself rather than crumbles away. The issue has been resolved but maybe you got unlucky and got old stock that should have been sent back. Sorry don't remember which manufacturer it was for sure but I think it was lems with the new bushing installed.
 

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If the rotors are confirmed warped from a dial reading, Try replacing the front wheel hub assemblies if your suspension is tight. I think that was my main culprit.
 

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You can't test for runout with worn bearings, they will mimic runout. The first step in setting up is to force the rotor towards and away from the center of the car to look for play in the bearing. If there is you replace the bearings and try again.
 

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So I know he loaded the suspension and torqued everything down correctly
My money is STILL on thrust arm bushings, even in spite of this. Last set I put on, I carefully had the weight on the car with all 4 corners up on ramps when I torqued them down, probably my 4th thrust arm job myself. One side leaked out all its oil within about 150 miles. I'm quite convinced (other similar reports) of some sort of manufacturing or quality defect with recent Lemforder parts. Go so tired of dealing with it I went to monoballs. Slightly degraded ride quality, but MUCH more controlled and best of all I'll probably never need to worry/wonder about them causing brake shimmy again! At any rate, go underneath the car and inspect the bushings for the telltale signs of any leakage; I suspect you'll find some. . .
IMG_20191007_155940 (1).jpg
 
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