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

We're having a conversation among friends when one casually mentions
his wife's rotors "warped".

The other jumps on him and declares that street-use rotors don't warp (in
general). An Internet search bears him out, as MANY articles say rotor
warp is a myth.

Googling, we find that brake torque variation is mostly from uneven pad
deposition buildup (i.e., disc thickness variation) and axial runout. But
then it gets confusing as the more enlightened sources begin to mention
thermo elastic instability hotspots and breaking judder into low
frequency cold judder and high frequency hot judder.

The heated discussion went on. And so did the confusion.
For more than a few beers.

My question?

While we now know rotors rarely actually warp, does anyone know of a good
scientific or engineering paper explaining the TRUE causes of brake
related judder in street cars?

On Feb 14, 11:44*pm, Joe Mastroianni > wrote:
> does anyone know of a good
> scientific or engineering paper explaining the TRUE causes of brake
> related judder in street cars?

Here's 8 pages of "words"... that conform to what I think I might have
once known.
http://www.powerbrake.co.za/download..._01_judder.pdf
-----

- gpsman

On 02/14/2013 08:44 PM, Joe Mastroianni wrote:
> We're having a conversation among friends when one casually mentions
> his wife's rotors "warped".
>
> The other jumps on him and declares that street-use rotors don't warp (in
> general). An Internet search bears him out, as MANY articles say rotor
> warp is a myth.
>
> Googling, we find that brake torque variation is mostly from uneven pad
> deposition buildup (i.e., disc thickness variation) and axial runout. But
> then it gets confusing as the more enlightened sources begin to mention
> thermo elastic instability hotspots

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


> and breaking judder into low
> frequency cold judder and high frequency hot judder.
>
> The heated discussion went on. And so did the confusion.
> For more than a few beers.
>
> My question?
>
> While we now know rotors rarely actually warp, does anyone know of a good
> scientific or engineering paper explaining the TRUE causes of brake
> related judder in street cars?

there's no need for and "engineering or scientific" paper on this stuff
- it's trivial for anyone that's done the right disciplines in
engineering and/or materials.

as to the origin of how it affects the car, the pulsing effect you get
is a result of two factors:

1. local elastic distortion of the disk/hub interface.

2. use of single-piston/single-sided brake calipers.

#2 is particularly relevant because before they came along, brake disks
were still subject to the same distortions they ever were, but any
side-to side variance has hydraulic pressures balanced within the
caliper so they're not felt at the pedal. with single-sided, the weight
inertia delta between pushing a piston, then pulling the whole caliper,
creates a strong pulsing effect at the pedal. hence #1 becomes much more
noticeable.

bottom line, it's simple enough to fix, and simple enough to diagnose.
just stay away from hysterical internet bull****ters, clean your hub
interfaces, use a little antiseize and a torque wrench, and you'll be fine.


--
fact check required

On 02/15/2013 10:52 AM, gpsman wrote:
> On Feb 14, 11:44�pm, Joe Mastroianni > wrote:
>> does anyone know of a good
>> scientific or engineering paper explaining the TRUE causes of brake
>> related judder in street cars?
>
> Here's 8 pages of "words"... that conform to what I think I might have
> once known.
> http://www.powerbrake.co.za/download..._01_judder.pdf
> -----
>
> - gpsman
>

words, but not a paper, just advertising.

their cited uneven disk thickness is relatively uncommon. distortion
from the plane is very common indeed. it's the asymmetry of a caliper's
component momenta that causes pulsing in the hydraulics. opposed
pistons dynamically self-equilibrate - single sided calipers cannot.


--
fact check required

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/Ce...n%20Theory.pdf

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

POWERBRAKE: The final word on brake judder and "warped" discs
http://www.powerbrake.co.za/download..._01_judder.pdf

BREMBO: Judder caused by improper bedding procedure
http://www.brembo.com/en/car/Racing/...20CATALOGO.pdf

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/publicat...7d38711887.pdf

A Parametric Study of Brake Roughness
Robert Bosch Corporation
http://sem-proceedings.com/20i/sem.o...-Roughness.pdf

Judder, Diagnosis, & Prevention,
Mohamed Khalid Abdelhamid, AlliedSignal Automotive, Europe
http://sem-proceedings.com/14i/sem.o...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/d...mputations.pdf

Experimental Analysis of Disc Thickness Variation Development in Motor Vehicle Brakes
School of Aerospace, Mechanical & Manufacturing Engineering (SAMME)
http://researchbank.rmit.edu.au/eser.../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/conferen...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/afie...009_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_P...l_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 wrote:

> bottom line, it's simple enough to fix, and simple enough to diagnose.
> just stay away from hysterical internet bull****ters, clean your hub
> interfaces, use a little antiseize and a torque wrench, and you'll be fine.

Most seem to say it's uneven pad deposition causing DTV
where the pad deposition is self inflicted by the driver.

So, the best cure is to change your driving habits.
At least that's what most say.

On 02/15/2013 05:49 PM, Zen wrote:
> jim beam wrote:
>
>> bottom line, it's simple enough to fix, and simple enough to diagnose.
>> just stay away from hysterical internet bull****ters, clean your hub
>> interfaces, use a little antiseize and a torque wrench, and you'll be fine.
>
> Most seem to say it's uneven pad deposition causing DTV
> where the pad deposition is self inflicted by the driver.
>
> So, the best cure is to change your driving habits.
> At least that's what most say.
>

that's doesn't in the least explain how i go to a shop for tire
replacement, and driving home, my disks are "warped". i take the wheels
off, clean up the hub, torque with a three-stage sequence, and then my
disks are unwarped again.


--
fact check required

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/publicat...7d38711887.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.o...-Roughness.pdf

etc.

>
> Judder, Diagnosis, & Prevention,
> Mohamed Khalid Abdelhamid, AlliedSignal Automotive, Europe
> http://sem-proceedings.com/14i/sem.o...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/d...mputations.pdf
>
> Experimental Analysis of Disc Thickness Variation Development in Motor Vehicle Brakes
> School of Aerospace, Mechanical & Manufacturing Engineering (SAMME)
> http://researchbank.rmit.edu.au/eser.../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/conferen...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/afie...009_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_P...l_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

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

Joe Mastroianni > 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."