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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 04-01-2014, 12:55 PM
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bluebee bluebee is offline
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PICTURES requested of the measurements of a permanently distorted "warped" E39 rotor

In a recent thread, the age-old discussion of (repeated) so-called permanent distortion (i.e., warped rotors) occurred (again) today:
- Warped rotors again, by Aioros

I do not wish this thread to be another (repeat) discussion of whether rotors actually warp (as in potato chip) in practice or not, as that is already covered in the links posted to Aioros' thread listed above.

I simply ask for PICTURES of proof of a BMW E39 permanently warped rotor used in street driving.

#1. After having read EVERY thread referenced in the bestlinks, and having never seen a single instance of PROVEN (with pictures & measurements) physically deformed BMW E39 street-use rotors (many unproven allegations aside), all I ask for in this thread, is proof.

#2. The reason it matters is that, while the short term solution (i.e.,machined or new rotors) to most causes of rotor-related vibration (e.g., BFV, DTV, runout, etc.) can be the same, the LONG TERM solution is wholly different depending on the cause of the brake pedal pulsation.

For example, if the pedal pulsation that people attribute to so-called "warp" is actually due to repeated uneven pad deposits, then, while the short-term solution would be to either rebed, machine, or replace the rotors, the LONG TERM SOLUTION to uneven pad deposits would be to change your bedding and braking habits (by not clamping hot pad to hot rotor after a hard stop, for example).

I'm not sure what the long-term solution to repeated brake rotor distortion would be, but I doubt it would be the same as with uneven pad deposition.

The correct long-term solution to repeated pedal pulsation is why this question matters!

Hence, this thread is opened to archive any proof of permanently distorted E39 street rotors that exists. If such proof exists, it should be shown here, as the intent is to refer to this thread in the future, when the subject (inevitably) comes up, regarding repeated pedal pulsation attributed to permanent rotor distortion.
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Last edited by bluebee; 04-13-2014 at 03:15 PM.
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  #2  
Old 04-01-2014, 01:13 PM
aioros aioros is offline
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i will try to get a dial to check the rotors and post the results here.
fyi Bee, there is no pedal pulsation in the car, that i have noticed but as soon as i press the brake pedal, the steering wheel shakes side to side (like if i was trying to turn the wheels right to left, left to right in a very short movements)
I've been thinking of video taping the steering wheel while is shaking actually.

Sent from BimmerApp mobile app
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  #3  
Old 04-01-2014, 01:52 PM
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Not a bmw but gives an idea of it.

I wish I kept some of the really bad warped ones Ive seen. Ive seen them warped so bad the wheel wouldnt turn.
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  #4  
Old 04-01-2014, 01:53 PM
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bluebee bluebee is offline
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Quote:
Originally Posted by aioros View Post
there is no pedal pulsation in the car, that i have noticed but as soon as i press the brake pedal, the steering wheel shakes side to side
I see others (such as cn90, RDL, bobdmac, etc.) have offered their very detailed and astute advice in your thread on what to look for with respect to steering wheel vibration due to BFV, DTV, or deformed rotors, so, I just re-reference that thread for the differential diagnosis of disc distortion versus brake force variation and disc thickness variation:
- Warped rotors again, by Aioros

Meanwhile, we'll use this thread to add conclusive proof of permanently distorted rotors (so that it may be a useful reference, now, and in the future).
So far, there isn't any proof yet, of a permanently distorted rotor, but my hope is that someone can provide the pictures of the measurements.

Meanwhile, here are some reference articles on so-called "warped" rotors:
- Warped Brake Discs, by Michael Grant
- Warped Rotor Myth, by Beandip
- Avoiding Brake Judder at the Track, by Dave Zeckhausen
- Brake Rotor Shake Demystified, by Dali Racing
- The "Warped" Brake Disc and Other Myths of the Braking System, by Carroll Smith
- 8 Myths ... Holding You Back from Performing the Best Brake Job, by Andrew Markel
- Brake Roughness and Vibration: Causes & Solutions, by Dave Mann
- There's no such thing as 'warped' brake rotors, by Michael Block
- Raybestos Brake Tech School, Part One: Rotors Don't Warp, by Police Fleet Manager Magazine

And, attached, are some pictures of what people THINK is a warped rotor, but, which, in reality, are pad imprints causing either BFV or DTV (and not permanent distortion):









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Last edited by bluebee; 04-13-2014 at 04:20 PM.
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  #5  
Old 04-12-2014, 11:01 PM
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bluebee bluebee is offline
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Quote:
Originally Posted by aioros View Post
i kept the old rotors to verify if warped.
If someone has an idea how Aioros can prove permanent distortion in the now-removed rotors, now is the time to suggest a testing method please!
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Last edited by bluebee; 04-13-2014 at 04:17 PM.
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  #6  
Old 04-12-2014, 11:40 PM
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Best way Ive found is the put it on a brake lathe just done turn them with the cutting bit. Just spin it and film it. Warped rotors are easy to see that way.

Heck just putting them on a flat table will show the warped part.
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  #7  
Old 04-13-2014, 04:12 PM
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Quote:
Originally Posted by crowz View Post
just putting them on a flat table will show the warped part.
I was wondering if just putting a straight edge on the rotor would show "light" somewhere if it's warped?

What are we expecting by way of distortion with a feeler gauge? 0.002" or so?
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  #8  
Old 04-13-2014, 04:38 PM
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The ones I label warped will show up with a straight edge with light shining thru thus a feeler gauge will show how much just like checking the deck on a block or the surface of a car head.
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  #9  
Old 04-14-2014, 06:58 PM
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stigst3r stigst3r is offline
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I encounter warped rotors in the past, The rotors were brand new and the vender refused to replaced them even though i send them this video:



it was a little dangerous driving with them, i remember once having to brake from 70mph down to 50 and it was really unpleasant.
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  #10  
Old 04-14-2014, 08:27 PM
Burning2nd Burning2nd is offline
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i wouldnt have sent you new rotors either..

your doing it wrong..

you have to indicate first..
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  #11  
Old 05-15-2014, 07:45 PM
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Quote:
Originally Posted by stigst3r View Post
The rotors were brand new and the vender refused to replaced them even though i send them this video
I like that video since I hadn't expected any measurements to be posted, actually, since it's my understanding that true distortion warp doesn't really exist (on typical street-use E39s).

But it was a surprise to see the measurement done on the vehicle - since I - personally, don't see how anyone can reliably measure distortion while the rotor is on the vehicle.
(But that's why I had asked for a picture of the measurement of the permanent rotor deformation.)

In that video, assuming the rotor was previously mic'd for parallel rotor faces (i.e., DTV within spec), and assuming that the lug bolts were properly torqued, what I see is about 10 thousandths of an inch of lateral "runout" in that video.
Lateral runout is not the same as permanent distortion.

This is a diagram of lateral runout:

Unfortunately, E39 lateral runout is a hard spec to locate (I've tried), so I can't tell you if 10 thousandths of an inch of runout in the video above is to spec or not:
- Where is the published brake disk/disc lateral runout specification for the BMW E39?

Most of us guess that about 0.002" of lateral runout is the most we should see on the E39; so, in that case, I'd agree that the lateral runout shown in that video is probably excessive.
But there's nothing in that video that indicates that the rotor is the problem.
While rotor DTV may be the cause of that 0.010" measured lateral runout, it could just as well be caused by improper lug-bolt torque or even a small burr or rusty debris on the hub, neither of which would implicate the rotor as being faulty.

To clarify, for the purpose of this thread, we can assume that I'm not asking for pictures of how to measure lateral runout, nor how to measure disc thickness variation:

What we're asking for in this thread is a picture showing how to measure warp (i.e., permanent distortion) on an E39 street-use rotor:
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Last edited by bluebee; 05-15-2014 at 08:39 PM.
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  #12  
Old 08-03-2014, 12:08 AM
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There's another case of "repeated warped rotors", this time to the left rotor, every time, over here today:
> E39 (1997 - 2003) > 540i sport keeps warping front left rotor

So maybe we'll finally get that picture of a warped rotor we've been waiting forever for (with over 300,000 visitors to the brake threads, you'd think at least one person would show proof of what they say).

Anyway, here's an excerpt of the OP's description:
Quote:
Originally Posted by 1hander View Post
since ive had it..2 years, it regularly warps the front left rotor only.

I put brembo drillred rotors on it thinking it needs more cooling for the way i drive.. but even if i drive chill..it warps a rotor every 3000 milles or so...on the button without fail, to the point that its no longer tolerable

i have 3 rotors that i cut and swap out on a regular basis,when i cant take it anymore...

any ideas why its just the front left
Quote:
Originally Posted by 1hander View Post
i do the proper break in, each time ive swapped out rotors, putting new pads and doing as told for bed in etc etc...even when i drive and come to stops i never hold the brakes if possible..

if its pad material being deposited unevely, then its definately being caused by a sticky caliper/piston

i understand the science but i cant get passed why when i turn the rotor in the lathe...it cuts unevenly ... until sufficient material is removed as its even again..and they keep mentioning pedal pulsation, mine is steering wheeling going side to side.. so maybe its something else
Quote:
Originally Posted by 1hander View Post
the pad wears abouyt the same on the left side
Quote:
Originally Posted by 1hander View Post
so i checked the hub for runout and immediately noticed the bearing is sick on the left side...had about .006 runout that would change high spots during rotation..

so at this point
ive ordered
2 new thrust arms
2 new brembo rotors
2 new calipers and carriers
2 new hubs and bearing
new set of green pads.
Quote:
Originally Posted by 1hander View Post
i thought i would update this... as you guys know ive been trying to fihgure out why only the front left is warping...

to date it has all knew control arms,hubs, bearings, idler arms...etc etc ...basically a completely new front suspension and steering, when i had the rotors cut , i tightened the wheels in a star pattern...hell ive replaced even the entire rear suspension just in case it was causing a problem..

i make sure to bed the pads in right, and i never keep my foot on the brakes at stops

after about 3900 milles, the front left rotor is shaking again...

ive also noticed that my 2006 x5 is afflilcted with the same disease, on it i replaced the whole left side suspension and at about 4k miles it starts to shake and as the mileage increases the shake worsens depending on how hot the rotors get

ive talked to my bmw mech and he says that they change alot of rotors because of the front left warping for some reason..so im at a loss i basically have two sets of rotors for both vehicles and i swap them out about every 18 months, i stopped driving so much....is the only fix i have come up with...i find it strange that my x5 warpds the same rotor...

thanks for all the help and insight fellas
Quote:
Originally Posted by 1hander View Post
unfortunately the front left rotor shake has rearerd its ugly head again...

after replacing all the control arms in the front, tie rod ends, centerlink, new spindles(bearings) , i even went as far as replacing both front spindle carriers, so the front end is brand new .... i modified the way i drive and use the brakes, never hold them down at a full stop... ive tried brembo rotors, dealership rotors.. it just takes longer for it to start shaking now... ive rebuilt the calipers with upgraded slider pin things,then bought new calipers and transplanted the pin set .. i tried drilled rotors, slotted rotors... like i said, it just takes longer but eventually it starts to shake when braking...

im at a loss, the only thing i can think now ... and im grasping at straws here, is that the chassis was maybe wrecked and is tweaked somehow... like i said grasping....

my next step is going to be going to bigger brakes...unless someone has another theory i can chase... thank you guys for all your input
Quote:
Originally Posted by bluebee View Post
I see you said you changed your braking habits, which might have staved off the vibration for a longer period of time. But, if it keeps coming back, it's not the rotors, and it's not the pads, nor is it likely the calipers.

I still think it's pad deposits, growing over time, but, if you think it's the equipment, you can go for larger calipers, pads, and rotors.

I'm just not sure how larger "stuff" will help. Sure, it will dissipate heat better, but, what's that got to do with vibration?
Quote:
Originally Posted by 1hander View Post
im at a loss for sure, i agree that the brake upgrade is awaste of money... even with just over 500hp at the wheels, the stock brakes seem to be up to the task of stopping the car with no problem...

it may very wheel be the pad deposits... my only argument with that, is why is it only the left rotor that shakes...always....never the right one.. my x5 has the same problem..only the left one,,never the right one...strange for sure...

you gave me and idea though....im going to remove the left rotor only and use a DA sander and sand both sides of the rotor to try to remove any pad deposits... the rotor surfaces are still pretty much completely straight with no grooves in them...if the shake goes away under braking then it is indeed pad deposits and bigger brakes will not do anything at all except make my wallet lighter..

what i have noticed is a squeek intermittent when im driving and pass by the divider walls and the sound bounves back...i looked at the rotor and on the inside only there is an approx 7 inch long scratch towards the very outside edge like its hitting something... the only thing it can make contact with is the pad... which means the rotor is wobbling, not sitting square on the hub...but its new so is the rotor, both surfaces were spotless when it installed them...which if it means what i think it means, the hub face or the face of the rotor is not perpendicular to the braking surfaces of the rotor..which means i need to buy another hub , buut what are the odds that the old one and the new i installed are out of spec for some reason...and what are the odds that the 4 different rotors, full face,slotted,drilled, brembo ..oem are out of spec, one would think that one of those boogers would be straight

i will post the results...
Quote:
Originally Posted by bluebee View Post
Uneven pad deposits "could" do that, but I agree, it's unlikely they'd always just happen on the left rotor. They'd probably happen on both, considering the conditions should be the same or similar.

How do you know it's the left rotor?

When mine pulsates, I can hardly figure out which axle, let alone which wheels are the ones vibrating.



That should work.
Let us know what happens.

You could also run a few re-bedding runs, and see if the vibration character changes (which is what seems to happen with me, although I can't explain why).
Quote:
Originally Posted by 1hander View Post
every time i have the rotors cut, cuz i have them both cut at the same time regardless of it being on ly the left....

the right rotor requires waaaaayyyyyy less cutting than the left...ive kept track of it and right now the left rotor is at the minimum thickness from being cut more than the right.. so if i keep cutting them at ths rate, im just guessing here but i think if i returned to my old braking and driving habits that i would go through 3 left rotors to one right rotor.. the way it used to be, i was having the left rotor cut about every 3 or 4 months..

ill try the sanding bit and see what happens ...

i need to change out the diff bushings ... the front one is shot . while im in there im gonna replace the input and output seals and the guibo..change the diff fluid... unfortunately i cant find any place that rents the tool necessary to do those bushings so i think im gonna have to spend the money on a tool that im only gonna use once in my lifetime lol
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  #13  
Old 08-24-2014, 11:09 PM
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bluebee bluebee is offline
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Maybe we'll get pictures of a measurement of warped rotors this time, on an E46 ...
Quote:
Originally Posted by mrg325i View Post
I have a warped rotor
Quote:
Originally Posted by bluebee View Post
In the entire time I have been on bimmerfest, even with 20,000 posts, and having read probably well over 100,000 posts, I have *never* seen anyone prove a warped rotor on a street-driven E46 or E39:
>PICTURES requested of the measurements of a permanently distorted "warped" street-use BMW brake rotor

Therefore, I suggest the OP read up on so-called "warped rotors" before proceeding any further on diagnostics:
- Why it's not rotor "warp" causing your vibration (1)

Now, everyone who self diagnoses their "warped" rotors actually solves the problem by replacing or machining the rotors, so, they almost always conclude they are a diagnostic genius.

But, the reality is, that the warped rotors almost always RETURN:
- Warped rotors again
- sport keeps warping front left rotor

So, the fundamental thing I'm trying to tell the OP is that, while replacing (or machining) the rotors will temporarily eliminate the vibration that is diagnosed as 'warped' rotors, the actual cause of the vibration is (almost) certainly NOT warped rotors.

Given that the diagnosis is wrong, but the solution is correct, the OP is doomed to repeat, until/unless braking habits are changed (in most cases).

The threads I referenced above explain everything I'm talking about, so this is old information to most of the folks reading this.
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