Re: Do you know of engineering papers for what people call brake rotor 'warp'?

[Joe Mastroianni]

On Fri, 15 Feb 2013 16:51:20 -0800, jim beam wrote:

> words, but not a paper, just advertising.

Yes, I'm looking for 'real' scientific engineering papers.

All these (which are decidedly NOT engineering papers!) say rotors
aren't warping, but as you noted, it might just be advertising.

CENTRIC: Pad and Rotor Bed-In Theory, Definitions and Procedures
http://www.centricparts.com/files/Centric%20White%20Paper%20C2-Bed-In%20Theory.pdf

AKEBONO: Brake Noise, Vibration, Harshness, causes
http://www.akebonobrakes.com/company/media_center/white_papers/akebono_NVH.pdf

POWERBRAKE: The final word on brake judder and "warped" discs
http://www.powerbrake.co.za/downloads/tech_01_judder.pdf

BREMBO: Judder caused by improper bedding procedure
http://www.brembo.com/en/car/Racing/Street-products/Documents/USA%20CATALOGO.pdf

[Joe Mastroianni]

On Fri, 15 Feb 2013 16:48:16 -0800, jim beam wrote:

> "thermo-elastic instability hotspots"?????? if you mean "heat
> distortion", then say so - don't try to confuse the proles.

The proletariat be damned, I reach out to the literati to explain
what "really" causes brake judder (because it's not rotor warp)!

Googling, I found these on the bimmer boards so far that I'm reading:

"Aspects of disc brake judder"
Proceedings of the Institution of Mechanical Engineers,
Part D: Journal of Automobile Engineering
http://pid.sagepub.com/content/217/6/419.full.pdf

Analysis of the vehicle brake judder problem by employing a simplified source–path–receiver model
Acoustics and Dynamics Laboratory,
Department of Mechanical Engineering,
The Ohio State University, Columbus, Ohio, USA
http://www.researchgate.net/publication/233988829_Analysis_of_the_vehicle_brake_judder_problem_by_employing_a_simplified_sourcepathreceiver_model/file/79e4150e7d38711887.pdf

A Parametric Study of Brake Roughness
Robert Bosch Corporation
http://sem-proceedings.com/20i/sem.org-IMAC-XX-Conf-S17P04-A-Parametric-Study-Brake-Roughness.pdf

Judder, Diagnosis, & Prevention,
Mohamed Khalid Abdelhamid, AlliedSignal Automotive, Europe
http://sem-proceedings.com/14i/sem.org-IMAC-XIV-14th-Int-14-5-5-Judder-Diagnosis-Prevention.pdf

Improved mathematical models of vehicle brake judder and experimental observations
Osman Taha Sen, Rajendra Singh
Acoustics and Dynamics Laboratory, Department of Mechanical and Aerospace Engineering,
The Ohio State University,
http://www.mecheng.osu.edu/adl/files/adl/C12-1.pdf

Judder vibration in disc brakes excited by thermoelastic instability
Oscar Altuzarra, Enrique Amezua, Rafael Avilés, Alfonso Hernández, (2002),
Engineering Computations, Vol. 19 Iss: 4, pp.411 - 430
http://www.ehu.es/compmech/welcome/doc/Paper%20867%20Engineering%20Computations.pdf

Experimental Analysis of Disc Thickness Variation Development in Motor Vehicle Brakes
School of Aerospace, Mechanical & Manufacturing Engineering (SAMME)
http://researchbank.rmit.edu.au/eserv/rmit:6260/Rodriguez.pdf

Thermal Brake Judder Investigations Using a High Speed Dynamometer
David Bryant, John Fieldhouse, Andrew Crampton and Chris Talbot, University of Huddersfield
http://eprints.hud.ac.uk/3878/1/2008-01-0818.pdf

Braking Process in Automobiles: Investigation of the Thermoelastic Instability Phenomenon
M. Eltoukhy and S. Asfour, Department of Industrial Engineering, College of Engineering, University of Miami
http://cdn.intechweb.org/pdfs/5380.pdf

Brake Vibration and Noise - A Review and Discussion
Dihua Guan, State Key Laboratory of Automotive Safety and Energy,
Tsinghua University, Beijing, China
http://www.acoustics.asn.au/conference_proceedings/ICA2010/cdrom-ICA2010/papers/p46.pdf

NVH Simulation Technology for Disc Brake Calipers
Hitachi, Suzuki Yoichi Kumemura Hayuru Inoue Yuichi Takagi Shinji Suzuki
http://www.hitachi.com/ICSFiles/afieldfile/2009/12/25/r2009_07_107.pdf

SURFACE TEMPERATURE DISTRIBUTION IN A COMPOSITE BRAKE ROTOR
A.A. Adebisi1, M.A. Maleque1 and Q.H. Shah
Department of Manufacturing and Materials Engineering
http://ejum.fsktm.um.edu.my/article/1146.pdf

DISCUSSION OF THE CHARACTERISTICS OF BRAKE JUDDER AND THE NECESSARY DATA ACQUISITION SYSTEM FOR COMPLETE ANALYSIS
D. Bryant, A. Crampton, J. Fieldhouse and C. Talbot
University of Huddersfield, Queensgate, Huddersfield HD1 3DH, UK
http://eprints.hud.ac.uk/3797/1/10_PAPER_Final_D_Bryant.pdf

Order domain analysis of speed-dependent friction-induced torque in a brake experiment
Osman Taha Sen, Jason T. Dreyer, Rajendra Singh
Acoustics and Dynamics Laboratory,
Department of Mechanical and Aerospace Engineering,
The Ohio State University, Columbus, OH 43210, USA
http://www.mecheng.osu.edu/adl/files/adl/J187.pdf

[jim beam]

On 02/15/2013 05:44 PM, Joe Mastroianni wrote:
> On Fri, 15 Feb 2013 16:48:16 -0800, jim beam wrote:
>
>> "thermo-elastic instability hotspots"?????? if you mean "heat
>> distortion", then say so - don't try to confuse the proles.
>
> The proletariat be damned, I reach out to the literati to explain
> what "really" causes brake judder (because it's not rotor warp)!
>
> Googling, I found these on the bimmer boards so far that I'm reading:
>
> "Aspects of disc brake judder"
> Proceedings of the Institution of Mechanical Engineers,
> Part D: Journal of Automobile Engineering
> http://pid.sagepub.com/content/217/6/419.full.pdf

quickly scanning, i see nothing on caliper asymmetry.

>
> Analysis of the vehicle brake judder problem by employing a simplified source–path–receiver model
> Acoustics and Dynamics Laboratory,
> Department of Mechanical Engineering,
> The Ohio State University, Columbus, Ohio, USA
> http://www.researchgate.net/publication/233988829_Analysis_of_the_vehicle_brake_judder_problem_by_employing_a_simplified_sourcepathreceiver_model/file/79e4150e7d38711887.pdf

that one presumes disk thickness variation, nothing on caliper dynamics.

>
> A Parametric Study of Brake Roughness
> Robert Bosch Corporation
> http://sem-proceedings.com/20i/sem.org-IMAC-XX-Conf-S17P04-A-Parametric-Study-Brake-Roughness.pdf

etc.

i'll try to look at the rest, but seriously, most people who don't know
are chasing their tails. those that do know aren't going to say much
because they're not going to do two things:

1. they're /definitely/ not going to kill a cash cow which is selling
new disks way before they're worn.

2. they're not going to stop using single-sided calipers because they're
essential to macpherson strut suspension being able to have a negative
scrub radius.

so you're just going to have to keep sucking it up and coughing it up.


--
fact check required

[Scott Dorsey]

Joe Mastroianni <j...@coohoo.com> wrote:
>All these (which are decidedly NOT engineering papers!) say rotors
>aren't warping, but as you noted, it might just be advertising.

Rotors warp for the same reason that lugs break off: idiots with lug wrenches.
It is correct that rotors do not warp by themselves, but I have seen plenty
of cases of warped rotors, all of which can probably be traced to some idiot
mistorquing lugs.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[jim beam]

On 02/15/2013 06:35 PM, Scott Dorsey wrote:
> Joe Mastroianni <j...@coohoo.com> wrote:
>> All these (which are decidedly NOT engineering papers!) say rotors
>> aren't warping, but as you noted, it might just be advertising.
>
> Rotors warp for the same reason that lugs break off: idiots with lug wrenches.
> It is correct that rotors do not warp by themselves, but I have seen plenty
> of cases of warped rotors,

did you mic them?

> all of which can probably be traced to some idiot
> mistorquing lugs.
> --scott
>

right, but that's not warping in the permanent sense that you can
measure off the vehicle, only in the elastic distortion sense that
disappears again as soon as you sort the wheel interface out properly.


--
fact check required

[Joe Mastroianni]

On Fri, 15 Feb 2013 18:34:14 -0800, jim beam wrote:

> i'll try to look at the rest, but seriously, most people who don't know
> are chasing their tails. those that do know aren't going to say much
> because they're not going to do two things:
>
> 1. they're /definitely/ not going to kill a cash cow which is selling
> new disks way before they're worn.
>
> 2. they're not going to stop using single-sided calipers because they're
> essential to macpherson strut suspension being able to have a negative
> scrub radius.

I'm reading those papers, as you are, and they talk about hot and cold
judder and they speak of high and low speed judder (mostly we're talking
around 100Hz here so that's low speed judder).

There's a lot of stuff about hot spots (I 'think' that's thermoelastic
instability) and disc thickness variation (I 'think' that's uneven
pad deposition) and axial runout (I think that's plane old runout).

It will also take me a while to read them all, but I don't see anything
(yet) about the single piston caliper design.

[jim beam]

On 02/15/2013 07:06 PM, Joe Mastroianni wrote:

well, it's pretty obvious if you consider the relative masses as a
dynamic system being agitated by a waving disk sat in its middle.


--
fact check required

[dsi1]

On 2/15/2013 5:06 PM, Joe Mastroianni wrote:
>
> I'm reading those papers, as you are, and they talk about hot and cold
> judder and they speak of high and low speed judder (mostly we're talking
> around 100Hz here so that's low speed judder).
>
> There's a lot of stuff about hot spots (I 'think' that's thermoelastic
> instability) and disc thickness variation (I 'think' that's uneven
> pad deposition) and axial runout (I think that's plane old runout).

I believe that what happens is that there's some transference of pad
material onto the iron disk at a molecular level. You can't measure it
because we're not able to measure tolerances to that level. It does,
however effect the frictional coefficients between the two surfaces at
localized areas. This causes the hot spots. Well, that's my
understanding about it anyway.

The pad material transference occurs mostly when the pads are hot. As a
practical matter, I try to ease up on the brake pressure after coming to
a stop after heating up the brakes.

[jim beam]

On 02/15/2013 10:53 PM, dsi1 wrote:
> On 2/15/2013 5:06 PM, Joe Mastroianni wrote:
>>
>> I'm reading those papers, as you are, and they talk about hot and cold
>> judder and they speak of high and low speed judder (mostly we're talking
>> around 100Hz here so that's low speed judder).
>>
>> There's a lot of stuff about hot spots (I 'think' that's thermoelastic
>> instability) and disc thickness variation (I 'think' that's uneven
>> pad deposition) and axial runout (I think that's plane old runout).
>
> I believe that what happens is that there's some transference of pad
> material onto the iron disk at a molecular level.

dude, absolutely there's transference "at the molecular level" - you
can't have friction without it. but to be grasping at straws as if
there's some kind of ghost in the machine that can't be explained any
other way is just ridiculous.

> You can't measure it
> because we're not able to measure tolerances to that level.

nothing personal to you, but that's complete b.s.

> It does,
> however effect the frictional coefficients between the two surfaces at
> localized areas.

only in some cases, with some kinds of pads. maybe 10% at most. all
the rest is plain old mechanical misalignment coupled [literally] to
poor dynamics of an unevenly weighted caliper.

> This causes the hot spots. Well, that's my
> understanding about it anyway.

it seems this is another one of those hose flap and antifreeze
electrolysis topics - a knowledge gap into which some people feel
compelled to inject good old underinformed guessing.

>
> The pad material transference occurs mostly when the pads are hot. As a
> practical matter, I try to ease up on the brake pressure after coming to
> a stop after heating up the brakes.
>
>>
>> It will also take me a while to read them all, but I don't see anything
>> (yet) about the single piston caliper design.
>>
>>
>>
>

--
fact check required

[dsi1]

On 2/16/2013 5:29 AM, jim beam wrote:
> On 02/15/2013 10:53 PM, dsi1 wrote:
>> On 2/15/2013 5:06 PM, Joe Mastroianni wrote:
>>>
>>> I'm reading those papers, as you are, and they talk about hot and cold
>>> judder and they speak of high and low speed judder (mostly we're talking
>>> around 100Hz here so that's low speed judder).
>>>
>>> There's a lot of stuff about hot spots (I 'think' that's thermoelastic
>>> instability) and disc thickness variation (I 'think' that's uneven
>>> pad deposition) and axial runout (I think that's plane old runout).
>>
>> I believe that what happens is that there's some transference of pad
>> material onto the iron disk at a molecular level.
>
> dude, absolutely there's transference "at the molecular level" - you
> can't have friction without it. but to be grasping at straws as if
> there's some kind of ghost in the machine that can't be explained any
> other way is just ridiculous.
>
>
>> You can't measure it
>> because we're not able to measure tolerances to that level.
>
> nothing personal to you, but that's complete b.s.

I'll regret it but OK, I'll bite - how would you measure rotor runout
that's only a few molecules thick?

[Joe Mastroianni]

On Sat, 16 Feb 2013 19:55:59 -0600, Vic Smith wrote:

> This pad deposition is new to me.

The "theory" (as I understand it) for the uneven pad deposition
based brake judder is that a little "hill" of as little as
15 microns (according to one of the papers we listed) will cause
low frequency (around 100 Hz) brake judder.

I'm still trying to figure this out, but apparently two things
happen at the same time when the pads hit the deposition "hill".

1. The pads "push back" causing the vibration to be felt in the
brake pedal.
2. The force varies, causing the entire suspension to shudder.

At least that's how I understand it after reading the (complex)
papers a few times. I'm still reading them though, so consider
this a preliminary explanation.

[Joe Mastroianni]

On Sat, 16 Feb 2013 19:55:59 -0600, Vic Smith wrote:

> I have very little experience with rotors that cause
> pulsation. Only times it happened with me was with old worn rotors
> that needed replacing anyway because they were grooved and eating
> pads.

An interesting aside is that we all have seen grooved rotors,
and we all know the "fingernail test" (i.e., if it catches your
fingernail, it's too deep) - but - if you LOOK UP the specs for
grooves, they have to be absolutely huuuuuuge (like the thickness
of a dime!) to fail a rotor.

At least in my experience.

If anyone actually has a bona-fide "groove" specification for their
rotor - please share!

[Joe Mastroianni]

On Sat, 16 Feb 2013 19:55:59 -0600, Vic Smith wrote:

> But here's what makes me believe that rotors CAN warp.
> And I'm not NOT saying that it the cause of most brake pulsation.

I should clearly state that I too believe rotors CAN warp!

However, what MOST people "call" warp, isn't warp at all.
It's merely brake judder.
Which, as we've seen from the dozen papers, can be caused by a LOT
of things. And, as shown by the industry advertising anyway, most
of the time it's NOT warp.

Plus, how would anyone know it's warp if they didn't measure the
rotors on the bench, as that's the ONLY way to tell a warped rotor
(as far as I can tell).

[bob haller]

my caravan carries a lot of weight, and the pads wear out
fast.........

Used to be garages demanded we turn the rotors, in my application they
would warp fast.

so now i just buy new rotors any time the pads get replaced.

my neighbor a highly skilled guy does lots of my vehicle repairs,
sadly i must find someone new.

he is a smoker and has lung cancer stage 4......

he is a good hard working guy i will miss him:(

[jim beam]

On 02/16/2013 08:40 AM, dsi1 wrote:
> On 2/16/2013 5:29 AM, jim beam wrote:
>> On 02/15/2013 10:53 PM, dsi1 wrote:
>>> On 2/15/2013 5:06 PM, Joe Mastroianni wrote:
>>>>
>>>> I'm reading those papers, as you are, and they talk about hot and cold
>>>> judder and they speak of high and low speed judder (mostly we're
>>>> talking
>>>> around 100Hz here so that's low speed judder).
>>>>
>>>> There's a lot of stuff about hot spots (I 'think' that's thermoelastic
>>>> instability) and disc thickness variation (I 'think' that's uneven
>>>> pad deposition) and axial runout (I think that's plane old runout).
>>>
>>> I believe that what happens is that there's some transference of pad
>>> material onto the iron disk at a molecular level.
>>
>> dude, absolutely there's transference "at the molecular level" - you
>> can't have friction without it. but to be grasping at straws as if
>> there's some kind of ghost in the machine that can't be explained any
>> other way is just ridiculous.
>>
>>
>>> You can't measure it
>>> because we're not able to measure tolerances to that level.
>>
>> nothing personal to you, but that's complete b.s.
>
> I'll regret it but OK, I'll bite - how would you measure rotor runout
> that's only a few molecules thick?

there's lots of ways, but that's not the point. the point is that
runout only a few molecules thick has absolutely no effect - surface
roughness alone of the disk is many orders of magnitude larger.

>
>>
>>
>>> It does,
>>> however effect the frictional coefficients between the two surfaces at
>>> localized areas.
>>
>> only in some cases, with some kinds of pads. maybe 10% at most. all
>> the rest is plain old mechanical misalignment coupled [literally] to
>> poor dynamics of an unevenly weighted caliper.
>>
>>
>>> This causes the hot spots. Well, that's my
>>> understanding about it anyway.
>>
>> it seems this is another one of those hose flap and antifreeze
>> electrolysis topics - a knowledge gap into which some people feel
>> compelled to inject good old underinformed guessing.
>>
>>
>>>
>>> The pad material transference occurs mostly when the pads are hot. As a
>>> practical matter, I try to ease up on the brake pressure after coming to
>>> a stop after heating up the brakes.
>>>
>>>>
>>>> It will also take me a while to read them all, but I don't see anything
>>>> (yet) about the single piston caliper design.
>>>>
>>>>
>>>>
>>>
>>
>>
>

--
fact check required

[jim beam]

On 02/17/2013 12:39 AM, bob haller wrote:
> On Feb 16, 9:18�pm, Joe Mastroianni <j...@coohoo.com> wrote:
>> On Sat, 16 Feb 2013 19:55:59 -0600, Vic Smith wrote:
>>> But here's what makes me believe that rotors CAN warp.
>>> And I'm not NOT saying that it the cause of most brake pulsation.
>>
>> I should clearly state that I too believe rotors CAN warp!
>>
>> However, what MOST people "call" warp, isn't warp at all.
>> It's merely brake judder.
>> Which, as we've seen from the dozen papers, can be caused by a LOT
>> of things. And, as shown by the industry advertising anyway, most
>> of the time it's NOT warp.
>>
>> Plus, how would anyone know it's warp if they didn't measure the
>> rotors on the bench, as that's the ONLY way to tell a warped rotor
>> (as far as I can tell).
>
> my caravan carries a lot of weight, and the pads wear out
> fast.........
>
> Used to be garages demanded we turn the rotors, in my application they
> would warp fast.
>
> so now i just buy new rotors any time the pads get replaced.

which is what most people do. it "works" because the new disks are
clean and thus seat properly. if old disks were properly cleaned, they
would too, but since time is money for shops, and disks relatively
cheap, replacement is in fact an economic option.

>
> my neighbor a highly skilled guy does lots of my vehicle repairs,
> sadly i must find someone new.
>
> he is a smoker and has lung cancer stage 4......
>
> he is a good hard working guy i will miss him:(
>

--
fact check required

[bob haller]

he has very little time according to his doctor.

its sad people get addicted to smoking then spend horrendous amounts
of money to get sick and die

[dsi1]

On 2/17/2013 5:49 AM, jim beam wrote:
> On 02/16/2013 08:40 AM, dsi1 wrote:
>>
>> I'll regret it but OK, I'll bite - how would you measure rotor runout
>> that's only a few molecules thick?
>
> there's lots of ways, but that's not the point. the point is that
> runout only a few molecules thick has absolutely no effect - surface
> roughness alone of the disk is many orders of magnitude larger.
>

If there's lots of ways, please name one of those ways. Just one. My
point is that I'm not talking about surface roughness. Just the
mechanical plating of pad material onto the cast iron surface.

[jim beam]

On 02/17/2013 10:51 AM, dsi1 wrote:
> On 2/17/2013 5:49 AM, jim beam wrote:
>> On 02/16/2013 08:40 AM, dsi1 wrote:
>>>
>>> I'll regret it but OK, I'll bite - how would you measure rotor runout
>>> that's only a few molecules thick?
>>
>> there's lots of ways, but that's not the point. the point is that
>> runout only a few molecules thick has absolutely no effect - surface
>> roughness alone of the disk is many orders of magnitude larger.
>>
>
> If there's lots of ways, please name one of those ways. Just one.

are you serious? i hope not.

> My
> point is that I'm not talking about surface roughness. Just the
> mechanical plating of pad material onto the cast iron surface.

dude, seriously, how do you think adding a "molecular layer" to a disk
surface makes the slightest difference? surface roughness is in the
order of 10 microns. that's at least 10,000 times bigger than even a
huge "molecular layer".

oh, and oem runout tolerance is ~10 times greater than that.


--
fact check required

[dsi1]

On 2/17/2013 4:32 PM, jim beam wrote:
> On 02/17/2013 10:51 AM, dsi1 wrote:
>> On 2/17/2013 5:49 AM, jim beam wrote:
>>> On 02/16/2013 08:40 AM, dsi1 wrote:
>>>>
>>>> I'll regret it but OK, I'll bite - how would you measure rotor runout
>>>> that's only a few molecules thick?
>>>
>>> there's lots of ways, but that's not the point. the point is that
>>> runout only a few molecules thick has absolutely no effect - surface
>>> roughness alone of the disk is many orders of magnitude larger.
>>>
>>
>> If there's lots of ways, please name one of those ways. Just one.
>
> are you serious? i hope not.

Oh yeah, "there's lots of ways" - none of them are serious. Nothing
personal, but you're the dude that full of bs. You don't even know what
the heck I'm talking about. Have a nice life dude.

[jim beam]

On 02/17/2013 11:54 PM, dsi1 wrote:
> On 2/17/2013 4:32 PM, jim beam wrote:
>> On 02/17/2013 10:51 AM, dsi1 wrote:
>>> On 2/17/2013 5:49 AM, jim beam wrote:
>>>> On 02/16/2013 08:40 AM, dsi1 wrote:
>>>>>
>>>>> I'll regret it but OK, I'll bite - how would you measure rotor runout
>>>>> that's only a few molecules thick?
>>>>
>>>> there's lots of ways, but that's not the point. the point is that
>>>> runout only a few molecules thick has absolutely no effect - surface
>>>> roughness alone of the disk is many orders of magnitude larger.
>>>>
>>>
>>> If there's lots of ways, please name one of those ways. Just one.
>>
>> are you serious? i hope not.
>
> Oh yeah, "there's lots of ways" - none of them are serious. Nothing
> personal, but you're the dude that full of bs. You don't even know what
> the heck I'm talking about. Have a nice life dude.

i'm glad i didn't bother! i spent years of my life measuring stuff to
microns and below, so if you think i'm going to try to educate a guy
who's clutching at "molecular layer" straws and being hostile about it
because he can't be bothered to pay attention to fact or can't be
bothered to google, you need to think again.

>
>>
>>
>>> My
>>> point is that I'm not talking about surface roughness. Just the
>>> mechanical plating of pad material onto the cast iron surface.
>>
>> dude, seriously, how do you think adding a "molecular layer" to a disk
>> surface makes the slightest difference? surface roughness is in the
>> order of 10 microns. that's at least 10,000 times bigger than even a
>> huge "molecular layer".
>>
>> oh, and oem runout tolerance is ~10 times greater than that.

just as i suspected, the relevant stuff is way over your head.


--
fact check required

[jgar the jorrible]

I had a 1979 Plymouth Champ Twin-Stik I bought new. With about 5K
miles on it, I took it on a hairball trip through the Sierras. By the
end of the trip, the rotors were definitely warped. The dealer didn't
have the special tool that car needed to remove the rotors, no one had
needed it yet. So given the choice of waiting several weeks for one
to be shipped from Japan, or machining their own tool, they made their
own tool. At least, that's what they told me, and I can't imagine
them making up stories to make more problems, work and expense for
themselves.

Man, that was a little pocket rocket, before the term was invented.
And I thought that coming from a '63 Vette.

Thanks for the judder links, Joe.

jg
--
@home.com is bogus.
Near my work: http://www.nbclosangeles.com/news/local/Tustin-Orange-County-Freeway-Shootings-191813631.html