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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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  #226  
Old 10-11-2012, 04:50 PM
Ted Milner Ted Milner is offline
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bluebee:
As a male, I would like to apologise for the many comments made by my gender denigrating your tireless efforts to get a job done right, the first time.

I'm just about to replace the front rotors and pads on my 03 525iT and am using you material as the most through and complete set of instructions I have seen on the net, including videos, blogs etc.

Your job obviously leads you to your extensive research on a subject with witch you have little knowledge, but I am grateful for you efforts and desire to share your data. I too do a lot of research before buying anything over $100, or before tackling new or infrequent jobs, like a brake replacement.

Thanks for the info., and ignore the macho "Just get the damn thing done" guys who would never admit to their mistakes.
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  #227  
Old 10-14-2012, 12:38 PM
Ted Milner Ted Milner is offline
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Did the fronts on my 03 525iT, followed your instructions to a T. Car stops like a jet grabbing the wire on an aircraft carrier, even, straight with wonderful pedal feel. Obviously the Brembo rotors and PBR ceramic pads are most of the reason, but following your instructions made everything perfect. Only complaint, the big G's that occur now.
Thanks for all your research and posts to make it so simple and having the confidence for doing it right.
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  #228  
Old 10-16-2012, 11:55 PM
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bluebee bluebee is offline
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Quote:
Originally Posted by Ted Milner View Post
I would like to apologise for the many comments ... denigrating your tireless efforts to get a job done right
Thanks for the kind words. I don't think it has as much to do with gender as with the fact that most people have the confidence to just 'do the job' without looking up how.

I don't have that confidence - but - as always - our strength is our weakness.

The strength of many who "just know" how to do it is that they get the job done fast and easily - yet - their weakness is they often do it 'wrong' (e.g., a BMW brake job is nearly dry if you ask Bentley).

On the other hand, I might do it right (because of the extensive research), yet it takes me forever to get the job done.

In the end, we need both types of people to cover the weaknesses and to add up the strengths. That's what a TEAM is all about!

Quote:
Originally Posted by Ted Milner View Post
am using your material as the most through and complete set of instructions
Thank you for recognizing the fact that EVERYTHING that I could think of answering 'is' in this thread (i.e., all torque figures, specs, measurements, fluids, decisions, tools, tricks, mistakes, suppliers, costs, etc.)
Quote:
Originally Posted by Ted Milner View Post
ignore the macho "Just get the damn thing done" guys who would never admit to their mistakes.
Thanks. I think, since this was my very first thread on Bimmerfest, folks were unaware of my propensity to keep asking and looking for answers - so it threw them off at first.

Quote:
Originally Posted by Ted Milner View Post
Did the fronts on my 03 525iT, followed your instructions to a T.
Fantastic! It makes me feel good to know that the team helped someone else, simply by typing our experiences and by posting our pictures!
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  #229  
Old 11-27-2012, 12:27 PM
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It's nice to know this thread (my very first on Bimmerfest) has helped others:
> E39 (1997 - 2003) > Brake Job Torque Specs
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  #230  
Old 01-17-2013, 08:48 AM
Richter12x2 Richter12x2 is offline
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Re: wear limit on rotors

I know this is an old thread, but want to point out the following. The wear limit is the limit down to which the rotors can be turned before they should be replaced. Turning rotors instead of replacing them points to the fact that they are intended to be useful for the term of a standard brake job at and above that limit.

Moreover, think of how brakes work - unless your rotor surfaces paper thin, it will still perform its intended function (i.e. stopping the car).

However, below a certain point, the rotor will be more prone to warpage as their will be less material to disperse the heat, and less structural rigidity due to thickness.

Therefore, it's perfectly fine to use rotors down to the number printed, (and technically beyond). When they warp, replace them.

In general, while all of the research is valid (and interesting!) the average driver will not notice a difference between rotors of varying thickness, brakes at varying hardnesses, etc. If you drive casually and not spiritedly, your deciding factors will be NVH. Noise, Vibration, and Harshness. If you're not stepping hard on the pedal repeatedly to brake (as a spirited driver would) then you probably won't notice differences in fade and initial bite.

So interesting as it is, it might be overkill for your project. I *do* second that I don't trust mechanics with my car if I can help it, though. But note that even though your car was built by engineers, it was designed to be maintained by mechanics, so there is wiggle room in the tolerances by design.

Quote:
Originally Posted by bluebee View Post
That's EXACTLY my question!

Thinking more along these newly logical lines ...

The rear rotors start at ~20mm (0.787 inches) and the wear limit stamped on the rear rotor is 18.4 mm (0.720 inches in the Bentleys).

If the wear limit is 0.720 inches for a rear rotor, I'm assuming that means the wear limit really isn't a wear limit, it's a pad-replacement limit. The true it's-too-thin-now wear limit would be, I'm logically assuming, 0.720 inches minus whatever is normally worn off the rotors during the lifetime of a single set of pads.

Given I have 60K miles, I'm assuming that's two sets of pads in the rear, and given the rotor started off at 0.787 inches and it's now roughly 0.727 inches, that makes it about 0.030 inches per pad set.

That would mean the TRUE wear limit for these rotors is 0.720 minus 0.030 inches, which is 0.690 inches.

Does this make logical sense to you that, in summary, each set of pads eats up about 0.030 inches of rotor, and that you can put pads on the rears at 0.720 inches, so, the true minimum thickness, after those pads are worn, would be 0.690 inches?

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  #231  
Old 01-17-2013, 09:41 AM
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Quote:
Originally Posted by Richter12x2 View Post
The wear limit is the limit down to which the rotors can be turned before they should be replaced.
I agree.
I suspect that limit isn't a mechanical strength limit so much as a heat-dissipation limit.

Quote:
Originally Posted by Richter12x2 View Post
unless your rotor surfaces paper thin, it will still perform its intended function (i.e. stopping the car).
I agree.
I suspect the danger is overheating, resulting in brake fade due to gassing.



Quote:
Originally Posted by Richter12x2 View Post
However, below a certain point, the rotor will be more prone to warpage as their will be less material to disperse the heat, and less structural rigidity due to thickness. ...When they warp, replace them.
I disagree.

The topic of warp is well covered in this thread, but see this reference outside this thread for details:
- Let's discuss the truth about rotor "warp" (1)

Quote:
Originally Posted by Richter12x2 View Post
the average driver will not notice a difference between rotors of varying thickness, brakes at varying hardnesses, etc.
I agree.
I suspect the only thing that will happen is that the rotors will not dissipate heat as well as they should - and - the result will be brake fade (I'm guessing so if others know better, please correct where I err).
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  #232  
Old 03-05-2013, 10:39 AM
mjbennett9 mjbennett9 is offline
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Quote:
Originally Posted by bluebee View Post
The first thing I noticed was there was no grease on either the spring or on the two 7mm caliper bolts. Checking the shop manual that came with the car, it says not to grease them. I wonder how they slide without being greased. Anyway, I decided to clean them with brake cleaner but it didn't really do much. I don't know what you guys do so you can suggest something here.

Moving on to the measurements......

Checking the rotors with my fingernail, they seemed to be in good shape with respect to smoothness. My fingernail didn't catch too much on any particular grooves and all were smooth. So the rotor passed the smoothness test.

I borrowed a mic to see how fat the rotors were......

I checked ten places just like the Bentley manual said. Pretty much all were in the .760 to 0.777 inch range which seems a bit small for the specification (0.800 inches). I wonder how they got so thin as they seemed in good shape otherwise.

Checking for warps, I borrowed a dial gage. Hooking it to keep it from wandering was problematic so I ended up vicegripping it to the spring and letting it hang down onto the rotor as I spun the rotor by hand from the lug bolts placed back in the lug holes.

I checked in a few concentric circles and all were within 0.002 or 0.003 inch. I didn't see a warpage spec in the Bentleys that came with the car. Did I miss that? It didn't seem to be in the brake section (page 340).
Hi BlueBee,

I've done my brake lines, rotors, calipers, and boots on calipers, so I feel like a "pro," but still learning. I too wondered about the grease on teh slide bolts/bushings on the caliper. I did grease them but after several months, I'm getting a noise when applying the brake. I know that could be a million things. I even brought the car in for a free inspection and of course they said it was nothing and reseated everything.

Since brakes are almost new, I suspect the only thing is that the calipers are sticking because of teh grease. It was fine when I was in the hot TX sun but here in FREEZING ohio, i suspect the grease is gelling up or something. I'm contemplating either cleaning the 10 year old bolts/bushings or replacing them. (roughly $20 per caliper if I recall).

I also wondered how the calipers would operate "dry." But if Bentley says not grease, it's probably ok.

Update to follow when I get some warm weather to do the job (no garage).
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  #233  
Old 03-05-2013, 04:17 PM
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Quote:
Originally Posted by mjbennett9 View Post
I also wondered how the calipers would operate "dry."
It's the age-old question. In fact, cn90 has a good thread on it right here today:
- To Lube or not to Lube Brake Guide Pin
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  #234  
Old 03-06-2013, 04:37 PM
retiredat44 retiredat44 is offline
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Thumbs up

I just ordered new rear rotors and pads, and will install them tomorrow, the previous owner didn't replace the rear brakes, and I believe the car still has the original brakes in the rear.. The rear rotors were too far scarred to save......

The oem replacements will only be about $150.00 (plus tax, and some incidental stuff added..). I am going through CARQUEST.

Then I need a tire, one of my tires has seen better days.. my wife said, I should take advantage of having the car now and take a long wanted trip.. My health is so damned bad, I could not travel alone.. but would love to hit the road...
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  #235  
Old 03-06-2013, 11:03 PM
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Quote:
Originally Posted by retiredat44 View Post
I believe the car still has the original brakes in the rear.. The rear rotors were too far scarred to save......
The original brand for the rear pads is Textar, so, if they're NOT Textar, they're not original.
As for scarring, in this thread it is well pointed out that "grooves" need to be extremely deep to fail a rotor (by BMW specs).

Quote:
Originally Posted by retiredat44 View Post
Then I need a tire
If you need "a tire", then you're best matching with what is on the vehicle.
See also the following, found by typing /tire F3 in the best links:
- How to logically choose tires by the numbers (1) (2) or by Bimmerfest user recommendations (1) (2) & where to buy your tires in the USA (0) (1) (2) (3) (4) (5) (6) & tire plant codes (1) (2) (3) & tire safety (1) & recommended tire pressures (1) (2) (3) & the claimed benefits of nitrogen gas (1) (2) & choosing the right BMW tire/tyre size (1) (2) & tire circumference, diameter, offset, & clearance calculators (1) (2) (3) (4) (5) & a torque conversion calculator (1) & tire terminology (1) (2) & wheel terminology (1) & BMW wheel specs (1) & BMW & replica wheel styles (1) (2) (3) (4) & the difference between cast vs forged wheels (1) & where to find the wheel markings for proper match mounting (1) & the best products for cleaning wheels (1) & how to choose the right size wheel spacers (1) (2) & where to go when you bend or otherwise damage your wheels (1)
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Last edited by bluebee; 03-06-2013 at 11:04 PM.
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  #236  
Old 03-06-2013, 11:45 PM
retiredat44 retiredat44 is offline
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Lightbulb

You can most likely tell when rotors have been damaged, they will look damaged and feel damaged, then the measurements will back that up. I used to replace rotors on several cars I have owned in the past.. Including a large custom van, but my Hondas and Toyotas never needed brakes often. You can see damage when the grooves cut into rotors like a butter knife through butter.

I also try to use parts sales persons with experience in the car I am working on. I get their feedback. I use forum feedback and info, a mix of information. And tailor it it to my families driving style, weather, and terrain. I add my 56 years of mechanical experience with building cars. Repairing cars. A wide variety of muscle cars, passenger cars, and the college courses I took, experiences, and life experience and all the reading and studying, and friends who had different cars and also rebuilt their cars. I then determine the medium cost of what I can afford, and durability, safety, recommendations.

Then all that determines on the replacement parts. I then am satisfied I purchase quality parts, not the best, but not the worst. Knowing my family is safe and the car performs as per designed. After this I would not hesitate to place it on mountain roads, the autobahn, and that my family will be safe with quality parts, that will perform to their best, for the quality at that purchase price, and since we want safety and do not perform reckless stunts, nor abuse the car, or push it past the laws of the roads we drive on. I am confident, the car is safe, and if I do decide to give it gas, it will also perform equally as well in braking as designed. I did my due diligence in choosing replacement parts and assembling them.

I will not hesitate to drive anywhere legal and enjoy the drive. And know we can be as safe as BMW intended.

It came with vented brakes and I am replacing the parts with what came off. Same with tires. Quality.

It will be fun and safe to drive!

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  #237  
Old 03-07-2013, 09:53 AM
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shaftdrive shaftdrive is offline
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Quote:
Originally Posted by retiredat44 View Post
I purchase quality parts, not the best, but not the worst
How do you know if one brake pad or rotor is better than another?
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  #238  
Old 03-08-2013, 01:02 PM
retiredat44 retiredat44 is offline
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I just replaced my rear brakes with Zimmerman rotors and Pagid pads. $200.00 included all parts, brake fluid, bleeder kit,. etc..
There are vented, slotted, drilled. The old ones were to far gone to save, they still had meat, but the grooves were too deep.

2001 530i
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  #239  
Old 03-08-2013, 02:23 PM
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Fudman Fudman is offline
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Quote:
Originally Posted by shaftdrive View Post
How do you know if one brake pad or rotor is better than another?
Relying on the opinion of others is the primary source of info for most product evaluations on this forum. Search for your product in question. Virtually every topic & product has been covered, in depth. As with any product selection, it is all about the tradeoffs. If you want max performance (best combination of brake bite & feel), stay with the OE brake pads (Jurid fronts & Textar rears). But they generate more dust than Pigpen. If you want clean wheels, go with a ceramic (e.g. Akebono). You will give up some braking bite & feel. In theory, all braking distances should be near equal since ABS is the great equalizer. When it comes to rotors, they are essentially the same. You can pay more for no rust coatings or bling (slots or holes), but none of it makes any difference in braking performance. The well known brands (Brembo, Zimmerman, etc.) are highly regarded, but hey, it is essentially a chunk of cast steel.
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  #240  
Old 03-08-2013, 04:06 PM
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bluebee bluebee is offline
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Quote:
Originally Posted by Fudman View Post
But they generate more dust than a Pigpen.
Somewhere, someone mentioned that it isn't so much they generate more dust than any other brake pad... it's just that their dust is dark color and therefore it stands out on the wheel, versus a more neutral colored dust, which, if the theory is true, doesn't show up as much.
Not sure if that's true though ... and I don't know how to test it ...
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Last edited by bluebee; 03-08-2013 at 04:07 PM.
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  #241  
Old 08-20-2013, 10:53 AM
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For the record, cn90 posted a decent suggestion for preserving the wear sensor in the last few thousand miles of pad life, over here today:
> E39 (1997 - 2003) > On the issue of brake pad sensor...

Adding valuable information, Poolman showed how to tuck the wires into the sensor junction box, when disabling the brake wear sensor permanently.

Quote:
Originally Posted by poolman View Post
I cut the wire on the sensor then connect the wires together and roll the wire back into the box--the sensors are never heard from again--we don't need no stinking sensors
And, Doru came up with decent logic for figuring out whether the OEM pads with the nub go on the inboard side or the outboard side:
Quote:
Originally Posted by doru View Post
I would think the nubs go on the outside, so it's a foolproof way of knowing when the pad(s) are done.
What I mean by that is: if the inside pad (which sits directly on the piston) wears before the outside - you will have the dash light telling you so. If the outside wears prematurely (sticking brakes, or some other anomalies), then you have the screeching sound.
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Last edited by bluebee; 08-21-2013 at 07:18 PM.
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  #242  
Old 09-22-2013, 09:38 AM
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For the record, the question came up yet again about the myth of BMW requiring new rotors with new pads, and RDL, among others, sets that myth to rest as busted.

Quote:
Originally Posted by rdl View Post
BMW doesn't think you need to replace the rotors when you replace pads. Here is a quote from TIS (BMW's service manual)
"New brake lining may only be installed if the brake disk thickness is greater than or equal to the minimum disk thickness (MIN TH)"

This makes it pretty clear that new rotors are not required unless the disks are worn. And there is no instruction to refinish back to as new surface - just check thickness and install new pads.

TIS provides data for refinishing disk surfaces, so BMW thinks that is OK too.

Some shops/mechanics will insist on new rotors since old rotors left untouched will occasionally develop braking problems with new pads. They don't want the aggravation of comebacks so claim that new rotors are "required" (not bothering to mention that the authority is they, themselves) Plus of course there is margin to be made on labor and extra parts.

TIS is silent on the issue of grooves in the disk. All that is specified is surface finish (roughness) on resurfaced disks. And residual thickness of course.
FWIW, an Opel (German GM) shop manual I have specifically OKs grooves up to 1mm deep. However, again many shops will insist on new disks or resurfacing, which will often take the disk below minimum thickness & therefore new disks again.
See also the attachment.
Attached Files
File Type: pdf BMW_E39_Brake_pads_and_rotors_DIY.pdf (1.73 MB, 5 views)
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Last edited by bluebee; 06-12-2014 at 08:41 AM.
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  #243  
Old 04-01-2014, 06:20 AM
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For the record, there's (yet) another warp thread today:
- Warped rotors again

Which included an interesting on-the-car rotor refinishing video:
Quote:
Originally Posted by hh3uunp View Post
See also the comment:
Quote:
Originally Posted by bluebee View Post
The OP feels brake related vibration.
There are many causes, but fewer solutions.

The most common solution, I agree, is to resurface or replace the rotors (which will work whether the true cause is "warp" or "DTV" and might even work for some causes of "runout").

The key issue that I have with thinking that (true) warp is the problem is that (the much more common) DTV related vibration can be caused by braking HABITS. If that is the true cause of the OP's repeated vibration, then it will happen to the OP again. And again. And again. And again.
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Last edited by bluebee; 04-01-2014 at 06:22 AM.
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  #244  
Old 04-01-2014, 12:32 PM
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bluebee bluebee is offline
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For the crosslinked record, I opened a new thread today to get to the bottom of how to measure permanently distorted BMW E39 street rotors:
- > E39 (1997 - 2003) > PICTURES requested of the measurements of a permanently distorted "warped" E39 rotor

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

I do not wish this thread to be a (age-old) question of whether rotors actually (repeatedly) warp in practice or not, as that is already covered in the links posted to that thread listed above.

I simply assert the two statements below regarding permanent distortion of BMW E39 street rotors, and then ask for PICTURES of proof of a BMW E39 permanently warped rotor used in street driving.

#1. I have read EVERY thread that I've referenced in the bestlinks, and have never seen a single instance of PROVEN (pictures & measurements) physically warped BMW E39 street-use rotors (many unproven allegations aside).

#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., DTV, runout, etc.) is 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 is simple (i.e., either machine or replace the rotors), the LONG TERM SOLUTION to uneven pad deposits is to change your bedding and braking habits (by not resting on the pedal after a hot 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.
Also, this post to the warped-again thread, repeats my assumption that the long term solution to pedal pulsation is different depending on the cause, while the short term solution may be the same whether the cause is DTV or permanent distortion.
- > E39 (1997 - 2003) > Warped rotors again

Quote:
Originally Posted by bluebee View Post
I realize some people won't want to hear this, but, I'm actually trying to help since pedal pulsation is often a REPEATED problem.

What I'm trying to say is that the short-term solution to pedal pulsation is the same whether the true cause of the vibration is permanent rotor distortion or uneven friction deposits ... but ... the LONG TERM SOLUTION is different!

Repeated pedal pulsation (especially with different combinations of pads/rotors), might not be heat related at all (hence, not due to pad choice nor to rotor or caliper choice, within reason).

I realize this is a hard pill to swallow, but, what I'm trying to say is that the long-term solution to repeated brake-related vibration might just be to change braking habits!

Most examples of so-called "warp" are actually due to uneven pad deposits.


Take a look at this article, for example:
- Warped Brake Discs, By Michael Grant
"
Every warped brake disc that we've investigated with the assistance of our suppliers shows uneven patches of friction material from the brake pads on the surface of the disc."

Let's say, for argument's sake, that your bedding and braking habits are actually what is causing uneven pad deposits. Would pedal pulsation occur repeatedly? Yes. Could it transcend pad choices? Yes. Could it transcend rotor choices? Yes.

Yet, short term, would it be solved with a new or turned rotor? Yes.

So, what I'm trying to say is that the LONG TERM solution to uneven pad deposits isn't the same as the long term solution to permanent rotor distortion.

BTW, I opened a new thread today, asking for proof, from anyone, of true permanent rotor distortion on a street-use BMW E39, since I have never seen such proof to date.
- PICTURES requested of the measurements of a permanently distorted "warped" E39 street rotor



I agree. I changed MY braking habits.
And, I replaced my rotors (machining doesn't seem to be cost efficient here in the Silicon Valley).
- One user's example of a complete brake job with all torque figures, specs, measurements, fluids, decisions, tools, tricks, mistakes, suppliers, costs, etc., that it entails (1)

However, my only point is that the short term solution to rotor-related pedal pulsation is the same, whether it's due to permanent distortion or to uneven pad deposits; but the LONG TERM SOLUTION to repeated pedal pulsation is different depending on the actual cause.

Luckily, the long-term solution to pad deposition is to simply change your bedding and braking habits!

Since the long-term solution is different, it matters what the cause is.
EDIT:
Quote:
Originally Posted by rdl View Post
First, keep in mind that a bad brake problem can shake the car so badly that it become difficult to determine if the pedal is pulsing or vibrating with the rest of the car.

Brake pedal pulsing always means that the caliper is forcing brake fluid back into the master cylinder. If there is a rotor thickness variation the mechanism is obvious. At the thick section of the rotor, the caliper piston must move backward into the caliper cylinder & push fluid to the master cylinder and thus move the pedal.

Then consider a truly warped (potato chip) rotor assuming no thickness variation and no uneven pad deposits.
If the warp is large or the speed is high
The distance the caliper must move is large &/or the movement is fast. So to move that distance in the rotation time, the acceleration must be high. This requires high force (Newton's 3rd law: F=ma) As the rotor pushes the pad/piston to one side, the caliper's inertia "pushes back." The brake fluid is squashed between the moving piston and the "wanting to be stationary" caliper and pulses back toward the m/c and pedal. We feel pedal pulse. If a front rotor, the force shaking the caliper is going to exert a torque on the steering axis => steering wheel shimmy. If a rear rotor, there will be a side to side force/vibration.

At smaller warps or slow(er) speeds
The caliper is still forced side to side during rotation as the pads/piston follow the rotor. But since the movement is small &/or slow, acceleration is low too. It doesn't take much force to move them back and forth. There isn't much pressure variation in the caliper cylinder and no pedal pulse is felt. Similarly, any vibration or steering wheel shimmy is reduced.

Taking this same line of thought on true rotors with uneven pad deposits (assumed to be infintesimally thin)
The piston and caliper are stationary, only brake torque is varying as the pads stick and unstick on the deposits. No pedal pulse since the piston isn't trying to push the caliper back and forth. One would not have any pedal pulse at any speed. There will be a general vibration in the car as the road wheel is pushed less and more toward the rear of the car. In addition if the varying brake force is acting on a front wheel it will generate a steering wheel shimmy as this varying force acts over the lever arm of scrub radius.

And to make things even more complicated, a badly warped rotor (a rare event) can result in one pad not making full contact over part of the rotation, i.e. behaves the same as uneven deposits. So diagnosis become more challenging.
Quote:
Originally Posted by rdl View Post
I don't believe one can reliably check thrust arm bushings to eliminate them as suspect.

I had at least one fail yet visual inspection and push/pull by hand and pry bar found no difference side to side. Once I removed them, one side bushing oozed a black oily liquid, the other side didn't. So at least one was in fact bad. With two new t-links my symptoms disappeared.

I then redid the push/pull tests. I found the compliance to be the same, or at least I couldn't tell the difference between before and after. I'd agree that this was not a scientific comparison of old to new or even side to side. OTOH, I've never seen BMW specs of force vs flex vs damping in order to perform an accurate measurement for pass/fail. Or the equipment to perform it.

It seems to me that the only practical avenue is to renew t-links or the bushings if you have the symptoms and no other less expensive suspect cause can be found.
Quote:
Originally Posted by rdl View Post
I don't think one can do so definitively. But one should keep in mind that if there is BFV in a front wheel there will be some steering wheel shimmy. However, steering wheel shimmy does not mean that the cause is BFV.

The braking force at the tire's contact patch is centered more or less at the scrub radius. If this force varies, there must be a varying torque applied to the steering gear & back to the steering wheel. A problem is that low levels of BFV can be difficult to confirm yet still cause steering wheel shimmy.

There are some avenues that I've used to narrow the probabilities. And I'm now assuming that tire balance and tire/wheel runout have been eliminated.

First, from say 20 mph, glide to a halt with a gentle brake application. If one can feel the car slow in a bit of a jerky motion, you have BTV. And the cycle should be repeating every tire rotation ~ 6 ft. (if you're really unlucky & have 2 or more sticky spots on one rotor &/or 2 or more brakes afflicted, you would have multiple jerks in the 6 ft. revolution) It may take several attempts to get the correct pedal force to detect this, if it is present. And by jerky I don't mean something that will pitch one through the windshield - rather just a sense that the car has run through a patch of molasses and then out of it again. It's also possible/likely that one could feel a slight, gentle twist of the steering wheel if the BFV is on a front wheel.

Another test for BFV is possible on the front wheels. Jack the car and then spin a front wheel fast enough for it to freewheel at least a couple of revolutions. Look for a spot in the rotation where the wheel slows more than elsewhere in the rotation. Or with repeated trials find that the wheel always comes to a stop in the same position, i.e. the sticky spot.

I think, but haven't ever tried to confirm, that these methods will work only if the BFV is due to either uneven pad deposits or formation of hard spots in the rotor. If the BFV is due to true warping, rotors cocked on the hub or rotor thickness variation:
# for the first test the dynamic effect disappears at slow speeds. But one should feel a gentle pedal pulse if the problem is rotor thickness variation
# for the second test the pads will be knocked back after a few revolutions and the effect disappears. But you might then hear the pads dragging slightly more at the sticky location in a revolution.

BTW, a shifted or separated belt in the tire may show up in the first test, although it's likely any BFV will be very subtle and the steering wheel twist relatively more pronounced. And one would expect vibration and steering wheel shimmy without braking. However I did once have a case where the tire problem was worst under braking because the braking force made the belt shift worse and this was noticeable only under moderate to heavy braking.
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Last edited by bluebee; 04-03-2014 at 03:49 PM.
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  #245  
Old 04-24-2014, 06:44 AM
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For the record, today was posted a thread where there might have been inadvertent damage to the brake lines, when the mechanic fails to support the heavy calipers during a typical brake job:
> E39 (1997 - 2003) > Brake Woes
Quote:
Originally Posted by helmet75 View Post
I installed my Brembo rotors and Akebono pads tonight. That went well- almost too well.
When I got the car in the air, I took off the drivers side tire and saw a small puddle of something wet. I looked up and saw a wet caliper. I looked up further and the brake line was VERY wet at the compression fitting to the rubber line.
So, now I have to park the car and get new lines on all 4 corners ASAP.
any recommendations? Here is what I'm looking at:
http://www.turnermotorsport.com/p-41...-approved.aspx

Is there any real difference in braided vs stock? anything concrete to show better pad pressure from braided lines?
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  #246  
Old 04-25-2014, 03:13 PM
bobdmac bobdmac is online now
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Mein Auto: 2001 540i/6, '90 BMW k75s
"Saloon," in a car context, is British English for "sedan."
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  #247  
Old 04-25-2014, 06:49 PM
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JDeGraff89 JDeGraff89 is online now
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Breaks were my first E39 DIY. Did all 4 in under 2 hours.. But I went the youtube route there were some very helpful videos
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Old 04-26-2014, 05:16 AM
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bluebee bluebee is offline
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I checked for "saloon" in the BMW acronym thread:
- BMW E39 technoterms, acronyms, glossary, definitions slang, technical terms, abbreviations (1)

It's not all that helpful:
Quote:
Bauart LIM = Body Type LIM (i.e., saloon)


So, I added Bobdmac's description.

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Old 05-15-2014, 06:31 PM
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Here is a nice video of runout for this thread:
> E39 (1997 - 2003) > PICTURES requested of the measurements of a permanently distorted "warped" E39 rotor
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:

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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Old 05-18-2014, 07:42 AM
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Quote:
Originally Posted by bluebee View Post
Looks like potentially another owner has a similar problem today:
> E39 (1997 - 2003) > Brake sensor

Quote:
Originally Posted by reestovee View Post
Question... my front brakes started making a metal on metal sound but the dashboard hasn't given me a check brakes light... whatz up?
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