Can anyone tell the difference between rotors and pads (truthfully)?

Wrong - been certified as a brake expert in Federal and State courts, having designed and built many kinds of brakes as well as brake testing machines for Detroit and Japan, and have done hobby work on race cars for 35 years - rotors warp out of plane. And I have pulled off a fair number of rotor plates that were definitely warped.
From your cite:
"The problem with this diagnosis and repair procedure is that first of all is that brake rotors do not warp. "
Wrong. They do, especially the ones that have offset bells. How can that be if the website says it can't?
Again, from your cite, as they state one sentence beyond where they say it does not exist.:
"Brake rotor disc thickness variation or excessive lateral runout, as well as drums that are out of round can cause vibrations and pulsations in the brake pedal and/or steering wheel. Brake lining material transfer onto the rotor can also have an effect on this as well."
Check out what they said about the rotor in their excerpts above- "it's not warped, it really just has its faces warped out of plane" yes, BS doubletalk is what you saw on that site. " It's not a duck, its really a mallard or its a bird with a green head that has webbed feet and quacks":
1) "Brake rotor disc thickness variation" means the planes of the rotor face are no longer flat with reference to each other, and if beyond allowable limits, each the face of the rotor has warped out of the permitted plane with respect to each other. That is called warp. (of the rotor face plane, the part the shoes contact).
2) "Excessive lateral runout" means the plane of the rotor face is no longer in the range of allowed plane, when measured by a runout gauge mounted externally to the rotor, and thus the face of the rotor has warped out of permitted plane. (to make a runout measurement - mount rotor in trued solid axle, set preloaded gauge on face, and turn rotor one turn while checking gauge to get max and min: subtract to get total runout) "Excessive lateral runout" can be due to excessive "brake rotor disc thickness variation" or bent mounts or twisted rotor.
Rotors are made thin so they can be light and keep fleet/vehicle mpg down. Even a first year engineering student can tell you how hard braking with the linkage turned hard over bends (warps) the rotor bell. (imagine 2 tons moving forward trying to go over a tire turned sideways with the brake pads locked onto the rotor, a rotor designed for transfer of force into floating claipers and transversely into the axle. Guess how the force gets from the 2 ton moving vehicle mass into the tire tread in a turn-- through the shoes gripping the rotor and back into the axle - forces across the rotor plane, unlike straight ahead braking, where the forces are in the rotor plane)
Any experienced engineer will tell you that if there is a problem and it goes way when you replace a part, the problem is gone. Was the problem the root cause and will it return? Well, if it wasn't part of the problem, the problem would still be there in some form. However, if it is only part of the problem, the problem will later manifest the same symptoms (E.g, if the driver brakes hard in corners, part of the problem, the rotors will again bend/wear the faces so that in time the plane of the rotor surfaces are no longer within tolerance, Before the driver got in and warped the new rotors, the new rotors were just fine)
( Logically, when you change the rotor and then the problem goes away, the problem is gone.)
and it seems the man ought to read the specs in the vehicle manuals, which do indeed list tolerances for rotors. And he ought to get some in depth background first. The internet is full of half-aware self-promoters with partially applied theories. And AMSOIL, no less.
FWIW - match mounting is a way to limit costly close tolerance machining in many mating parts- you make hundreds of parts all alike, and then measure them - some will be way off and get tossed, most will be within tolerance and used according to their tolerance, and some may even be perfect. It's cheaper than making each one perfect.
I'll put this quote from them in here for the experienced engineers to get a chcukle
"DTV is when the rotor thickness is not the same all the way around the rotor. DTV is typically caused by lateral runout. DTV can only be measured with very specialized laboratory testing equipment or with special on vehicle capacitance probes."
right.... ( or like a shop caliper or shop "mic", as noted in the maintenance manuals.)
Quote - "This [DTV] phenomenon is what many technicians refer to as "warping", however they actually think the rotor warped and needs replacement."
OK, so what they are saying is that the rotor isn't warped ( and so the rotor is true?) and the face of the rotor plane has just warped, and so they are saying that instead of the rotor needing replacing because the thickness varies, the rotor needs replacing because the thickness varies and the esoteric DTV measurements are lab things .(or you could just get refacing done at a brake shop, if enough material is left).
enough of quoting their home-spun humor....
There are regulations - Check out the following standards for brake materials: DE3A, BEEP, NHTSA FMVSS-105
From Toyota - why? aftermarket pads have few, if any standards. New-car brake pads (OEM) have to meet NHTSA standards, and thus actually do stop better, are more reliable, and the dust around the kids and dogs is less hazardous.
nuff free stuff

"hob" wrote in news:v5Sdnf-LU7B5LpXZnZ2dnUVZ snipped-for-privacy@comcast.com: Hi Hob,
Thanks for the wonderful detail to help all of us learn more to truly understand and accurately diagnose the real cause of brake shudder.
In a way, I'm sorry I referred to that one article which said brake rotors don't warp because other items in that article make us suspect they're biased somewhat.
However, this expert article is probably the best treatise on automotive brake pedal pulsation causes on the entire Internet which basically says the same thing!
...."Many technicians are under the impression that a "warped" rotor is one that has too much runout. They also attribute this "warping" to why the brake pedal pulsates. This is not true...."
So, just like we can't get colds & flu from being cold & wet (yet every mom & pop out there thinks we do), brake rotors (apparently) don't warp, yet every do it yourself garage mechanic thinks they do.
I'm glad we can have this dialog to help all of us (me included) better understand the cause and effect of brake pedal pulsation at high speed.
Stu
"hob" wrote in news:v5Sdnf-LU7B5LpXZnZ2dnUVZ snipped-for-privacy@comcast.com:

I'm as fascinated as you by all the theoreticians chiming in here, but I know one thing you don't seem to grasp, Stuie:
If you change the rotors, the pulsation will go away.
My opinion? You're shopping around for a way to blame Toyota - or anyone else - so you don't have to spring for the new rotors.

YEA... I've been trying to figure out... is the search "here" for an answer or is it just a debate? (In reference to the original poster). I think a number of people have posted some clear and concise answers.
Basically you can test anything under the sun if you have the money and time and along with that, the expertise.
Bottom line is that rotors indeed do warp, pads wear, and both need to be replaced over time. Some rotors warp for no apparent reason, some brake pads wear faster than others, some pads wear faster on the rear rotors and some pads wear faster on the front rotors. Depends on the vehicle, the brake setup / design, the type of pads / wear material, the thickness of the rotors and the makeup of the metal used...etc... I could go on and on.
You can find the solution you are looking for....just depends on where you look. If you don't like the answer look somewhere else and you might find someone with a different opinion. At least that what it looks like to me.
I don't waste my time looking at the links to the articles. Rotors and pads are "wear items" they don't last the life of the vehicle, they wear out.How you drive your vehicle and how well you maintain it play a large part in how long the vehicle lasts and how long the brakes last.
Like I said at the start...is the search for the answer or just to debate the issue.? ----------- Elbert snipped-for-privacy@me.com

Elbert wrote in news:g8op02hlu2mtffrvt1hp0t1h4n0ikemcrc@ 4ax.com: I think I've found most of the answers I needed although I'm currently working on the definition of "soap based lithium brake grease" at the moment (mainly because the lithium appears to merely be the saponification agent that congeals the oils used, which tells us nothing about which oils were used in the first place).
However, my thirst for the one and true answer aside, I must agree with you. After having read about fifty brake repair articles on the web, I can definately agree there's a lot of bad information out there.
Witness this Edmunds article I read today (filled with errors!):
I can count more than a half dozen errors in that article. Edmunds is doing a disservice to their clientele by publishing that article on the web.
For example, brake rotors almost never warp. Of course, they "can" warp. And you can get hit by lightening. But, they don't warp. What people call warp is not warp. It "feels" like warp. But it's not warp. That much is clear from reading scores of articles in the past week and asking questions and reading every answer over and over and over again.
You may disagree but that's the "answer" I found in this quest. That's why I am replacing the pads, rotors, and I will test the pistons this weekend for sticking. I'll replace them if need be. I'm looking up exactly how to pack the front wheel bearings at the moment. It's all obvious to me now, but it was NOT obvious to me when I originally asked the questions! With your help, I have arrived at the one and only truth.
It's the same with many things in life. Take that lightening bolt. I've asked dozens of people WHY your're somewhat protected in a car from a lightening strike. Know what almost all of the people asked said ('cept the electrical engineers?). Like those who say brake rotors commonly warp, almost all I asked mistakenly said what appeared so very obvious to them - that the rubber tires "insulated" the occupants from the lightening reaching the ground. Can you believe that? Like brakes warping, that erroneous answer "sounds" logical until you actually understand the dynamics of what is really happening.
Just like Galileo thought the curve of a chain hanging on two posts was a parabala, things aren't always what the easy answer would seem to suggest. Hell ... even the venerable Aristotle was wrong about the velocity of falling objects but his theories held for hundreds of years ... until Galileo actually put Aristotle theories to the true test.
One reason I "believe" the articles that tell us our brakes almost never warp is that the ones that talk about warp dont' seem to even recognize there ia the alternate view, while the ones which propose the alternate view always seems to know there is the prevailing presumption.
So, I pretty much have the answers to the questions posed. There are so many more questions that I'm researching but they are off topic for this thread.
Thank you all for helping me and the hundreds of others who read this, Stu

On Tue, 07 Mar 2006 07:53:44 GMT, "Stuart A. Bronstein" Gave us:
The FACT is that rotors "settle" or "stress relieve". What one is supposed to do is drive their car through one set of pads, and then get the rotors trued (read turned true) when getting the pads replaced.
This truing should only involve the removal of enough material to re-true the rotor. This is more prevalent a requisite in wet areas of the world where a very hot rotor may suddenly get quenched by a puddle or the like.
Anyway, the point is that once a rotor has been "seasoned" by said hot quenching after a set of pads has been worn through on the system, when it gets re-trued, it will NEVER warp again in nearly every case, and then the ONLY time the rotor will require replacement after that is if it gets gouged by a vehicle owner that doesn't keep his brake system in timely repair..
In other words, if done correctly, a "seasoned" rotor will outlast the vehicle after a single turning.
In dry areas like Southern California, where a brake system hardly ever gets subjected to a hot quench like they do in wet rainy or snowy areas, the rotor doesn't season as well, and may require more than one turing to keep it true.
There is no reason to ever replace a rotor that is still above the minimum thickness specification after a turning, and any respectable brake shop or automotive machine shop will turn an untrue rotor first, then check it, BEFORE suggesting that it needs replacement, and if it does turn out to be too thin, there is no charge for the turning if a new rotor is bought via the firm doing the turning. Also, they do NOT ever need to be replaced as a set. The minimum thickness spec is the ONLY spec for viability after ANY rotor has been attempted to be true turned.
I have done this with rotors as big as the Caterpillar rotors on the power take off of huge earth moving machinery with HUGE diameters.
True is true is true, no matter what any base level mechanic tells you.
Oh and by the way, YES, they DO warp, and if you are a mechanic, and have never worked in a machine shop, then you do not know.
Machined parts operate in a very specific manner. Unlike a corner in your house, which can be out of square and still be OK, a machined part MUST be true to its design all the way through. From your words it would appear that you do not know anything about fits and tolerances.
Rotors DO most certainly warp. ANY good shop knows this FACT, and any good shop knows how to tell if one has, both on or off the car.
It isn't about alternate views, it is basic mechanical engineering, and physics.
I welcome any rebuttals. I doubt you'll find any errors in my remarks, however.

. . {{HE says.......I sez}} . . ======== ======== Roy L. Fuchs wrote:{{or so he sez}} ............ ............ { I sez} ( That's FALSE info being posted in an open forum) (Be advised....you are stating mistruths) (You should recant now..before it's too late)
.............. ..............
{{He sez}} ........... ..........
{ I sez } {What a crock of crap} {Again, you should recant.} {YOU...are posting bad information}
........... ..........
{HE.......sez} ............... ..............
{I sez} {You ain't got a clue} {You reeeeely oughta rethink this} {You reeeeely oughta read what yer posting} {cuz yer wrong}
............... ..............
{HE..........sez} ........ ........
(I SEZ) {yer WRONG!!!!)
............ ............
(HE........sez) ............ ...........
( I SEZ) (rubbish) (you oughta pull a term of duty in icy city with a lot of stop lights)
............ ............
{{HE........SEZ) ............ ...........
(I SEZ) {i ain't gonna waste my time turning a pitted, rusty, gauged, rotor jest so's i can go call the wishfull thunk'n owner and tell em that all his hopefull wish'n ain't done a bit a good.....HE NEEDS A ROTOR!!)
(AND.......as for yer min. thickn. spec. being the ONLY spec for viability for replacement....well....what if, jest if, maybe, somehow, possibly, the bearing race won't hold in the rotor....think maybe, then, possibly, ......you might....suggest replacing the rotor then??)
(jest curious....as to yer absolutes)
(there will be a commentary at the end.....so read on dudely)
......... .........
(HE........SEZ.....) ........... ..........
(I sez) (I agree.....true is true) (I do believe however, that if ANY real world, skint knuckled, gray haired techs read this.....it's gonna be proven true that yer not posting truths)
............ ...........
(HE....SEZ) ........... ..........
{I SEZ} (i'm a mechanic) {in a past life...i worked in a machine shop) (for over 3 years) (i ran it) (i worked it) (i know do know) (you have proven to "me"...that you don't)
............. ............
{HE ........SEZ} ............... ...............
(I SEZ)
(uh..huh) (yer sounding like you don't know what you think you know you know.........you know)
............ ...........
(HE ....SEZ) ............ ............ ANY..??? ok.... here we go.....
(i wood like tuh sez) The only statement you made that sounded like anyone should listen to is the last one. Rotors DO most cerainly warp.
So.......let me git this correct. I stick a set of rotors on a vehical, go down the road, the brake pedal pulsates reeeellly bad.....and i tell the customer "Jest drive er till the pads wear out....and we'll fix er then."
git a life git a clue git more training
It's obvious by your post that you're extremely new to the trade, extremely inexperienced, young as hell, or....you ARE NOT a qualified brake technician. or, it might be all. (want me to define qualified?????)
so....which is it. you can pick more than one if you like.
any whooo....... you jest posted a crock of crap.
Explain to me....what you've based the fact that wet climates are causing a "more prevelant" "requisite" for rotors warping.
go ahead..... i've got time.... i'm will'n to listen...... and...i'm quite eager to hear it.
now...... Explain to me.....how it is, in all your experience, that you've NEVER...EVER..NEVER...once, put a rotor on a vehical and found it to cause a gawd-awfull vibration right out the box. I mean......you posting info that's make'n you seem to be a professional with knowledge of the trade. So..... you must check EVERY SINGLE rotor for runout straight out the box.........right?
uh..huh
now...... Tell me.....where you read that what one is supposed to do is "drive their car thru one set of pads".....and then git the rotors trued on the next pad change.
I done 1 or 2 brake jobs.....or more....and I ain't NEVER,EVER,NEVER, read.....EVER....heard that crap before.
and....i read alot.
and.....i study alot.
and....i go to classes alot.
and...i go to seminars alot.
and...i get, got, had, have, or was access to at one time....... some of the most prominant trade mags around.
and.....i ain't NEVER...herd dat befoe.
~~In Closing~~
As far as yer..."fits and tolerances"..
listen..wakeup...slap yerself...git a new job.... git away from whoever it is feed'n you all that crap...
cuz......yer little rant on how a rotor can or cannot warp, when it should or should not be replaced, tolerances and fit.... well...... you've told on yerself...you ain't got enough real world, hands on, life experience with brake service to be spewing forth info on it.
FACT...not fiction.
you closed with..and I quote " It isn't about alternate views, it is basic mechanical engineering, and physics."
you were correct on 2 statements..... rotors warp true is true
but....... it ain't basice mechanical eng. and physics dude....... it's the reeeeelll world.......
go do a thousand or so passenger cars, trucks, and vans......
then come back and tell us what you know.
~:~ MarshMonster ~show hopes you don't try to tell him you been do'n brake work for 20 years......he'll fall out his chair~ ========
========

On 8 Mar 2006 02:18:04 -0800, snipped-for-privacy@aol.com Gave us:
I knew more about fits and tolerances and precision machining at age ten in 1970, than your retarded ass will ever know in your entire pathetic life, dipshit.

On 8 Mar 2006 02:18:04 -0800, snipped-for-privacy@aol.com Gave us:
I did brakes 25 years ago, dumbass. Compared to engineering, it is a petty task.

======== ======== Roy L. Fuchs wrote: ======= ======= Roy...Boy Toy, go fix a Space Invader machine.... and leave all this confusing brake stuff to us Manly Men.
now .......
go along.......
engineer something......
go ahead.....
it ain't gotta work forever.....
some tech out there will FIX IT.
rotflmfao @ the PackMan technician.
hey roytoy.......you dropped yer slide rule.
~:~ MarshMonster ~slaps boytoyroy across the face with a greasy shop rag.... jest cuz he can~