On 12/5/2022 5:46 am, Alan wrote:
> On 2022-05-11 12:22 p.m., Andy Burnelli wrote:
>> Xeno wrote:
>>
>>>> Is "warp" the right word to use for a rotor (disc) that remains as a
>>>> flat plane but with a surface that is not uniformly smooth over the
>>>
>>> Short answer - no.
>>
>> Longer answer, verbatim... *Brake Rotors Warp From Heat -- Myth Busted*
>> <https://www.hansonsubaru.com/service/information/brake-myths.htm>
>>
>> 5. Brake Rotors Warp From Heat -- Myth Busted
>> Damaged brake rotors can cause your car to shudder and shake under
>> braking,
>> and that's often attributed to "warped" brake rotors. The suggestion
>> goes,
>> under intense, emergency, both-feet-on-the-pedal-type braking, the brakes
>> get so hot that the brake rotor warps and deforms. Since it's not
>> perfectly
>> flat anymore, it causes your car to shake when you engage the brakes.
>>
>> But that's a myth -- there's simply no way that a brake rotor can get hot
>> enough to warp or deform on an ordinary passenger car. However, this idea
>> of a 'warped' rotor is commonly used in reference to the surface that the
>> brake pads contact. This surface can become uneven and this is most
>> commonly caused by heat from emergency or aggressive braking. As the
>> brake
>> pads are held against an uneven rotor surface, the vehicle may shake or
>> shudder while stopping or you may notice that your brake pedal has
>> something of a bounce to it.
>>
>> So, while it's usually not technically accurate to say that a brake rotor
>> is warped, that term is still used to indicate that the surface of your
>> brake rotors is not even.
>
>
>
> Empiricism:
>
> <https://youtu.be/fFY2MPylrS4>
>
> See the big dark patch as that rotor is slowly being turned on the brake
> lathe?
>
> That's warp.
>
> As is this:
>
> <https://youtu.be/eEpYifYWV5k?t=250>

You're preaching to the converted. Well, not so much *converted* as
*aware*. I was doing disc and drum machining in the *70s*. I have seen
and done all of that guff, including all the measuring with appropriate
*workshop level* equipment.

--
Xeno

Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On 2022-05-11 6:35 p.m., Xeno wrote:
> On 12/5/2022 5:46 am, Alan wrote:
>> On 2022-05-11 12:22 p.m., Andy Burnelli wrote:
>>> Xeno wrote:
>>>
>>>>> Is "warp" the right word to use for a rotor (disc) that remains as
>>>>> a flat plane but with a surface that is not uniformly smooth over the
>>>>
>>>> Short answer - no.
>>>
>>> Longer answer, verbatim... *Brake Rotors Warp From Heat -- Myth Busted*
>>> <https://www.hansonsubaru.com/service/information/brake-myths.htm>
>>>
>>> 5. Brake Rotors Warp From Heat -- Myth Busted
>>> Damaged brake rotors can cause your car to shudder and shake under
>>> braking,
>>> and that's often attributed to "warped" brake rotors. The suggestion
>>> goes,
>>> under intense, emergency, both-feet-on-the-pedal-type braking, the
>>> brakes
>>> get so hot that the brake rotor warps and deforms. Since it's not
>>> perfectly
>>> flat anymore, it causes your car to shake when you engage the brakes.
>>>
>>> But that's a myth -- there's simply no way that a brake rotor can get
>>> hot
>>> enough to warp or deform on an ordinary passenger car. However, this
>>> idea
>>> of a 'warped' rotor is commonly used in reference to the surface that
>>> the
>>> brake pads contact. This surface can become uneven and this is most
>>> commonly caused by heat from emergency or aggressive braking. As the
>>> brake
>>> pads are held against an uneven rotor surface, the vehicle may shake or
>>> shudder while stopping or you may notice that your brake pedal has
>>> something of a bounce to it.
>>>
>>> So, while it's usually not technically accurate to say that a brake
>>> rotor
>>> is warped, that term is still used to indicate that the surface of your
>>> brake rotors is not even.
>>
>>
>>
>> Empiricism:
>>
>> <https://youtu.be/fFY2MPylrS4>
>>
>> See the big dark patch as that rotor is slowly being turned on the
>> brake lathe?
>>
>> That's warp.
>>
>> As is this:
>>
>> <https://youtu.be/eEpYifYWV5k?t=250>
>
> You're preaching to the converted. Well, not so much *converted* as
> *aware*. I was doing disc and drum machining in the *70s*. I have seen
> and done all of that guff, including all the measuring with appropriate
> *workshop level* equipment.
>

Oh, I understand that you understand.

But it's great that you've replied, as Arlen/Andy/....who knows how many
others...

....has me killfiled for providing exactly this kind of clarity.

On 12/5/2022 8:25 am, sms wrote:
> On 5/11/2022 5:47 AM, NY wrote:
>
> <snip>
>
>> I wonder what effect that high temperature had on the pads once they
>> were red hot. Would you want to ride in that car afterwards - would
>> the pads have been made less effective? How hot do discs get if you
>> descend a long hill (let's say a mile long, average 1:4 aka 25%) using
>> brakes only. My wife remembers a friend descending such a hill
>> (Porlock Hill in Devon, England) in a motor caravan which may have had
>> a mixture of discs and drums. By the end of the hill, there was smoke
>> coming from the wheels (brake pads, presumably) - the driver learned
>> an important lesson: to engage a low gear on a long steep hill so
>> there is a bit of transmission braking to supplement the normal
>> friction braking.
>
> Decades ago I replace the brake pads on a VW Rabbit (Golf in other
> regions) with pads that I ordered online from JC Whitney, a mail-order
> parts house. Descending a steep hill, in San Francisco, the pads glazed
> over from the heat. The rotors were fine. Did another brake job
> immediately, using high-quality pads from an import car parts store.
>
> Unfortunately, in the U.S., not a lot of vehicle owners still do their
> own car maintenance so the number of auto parts stores is greatly
> reduced. In my town of 60,000 people we've lost all three of our auto
> parts stores as well as a fourth that's just across the city boundary. I
> now buy my oil at Costco or Walmart and I order my oil filters from a
> dealer that sells OEM parts on eBay.
>
> Two of our vehicles are hybrids and because of regenerative braking the
> brakes last a very long time, easily more than 100K miles. On my old VWs
> I had to do brake jobs every 25K-30K miles.

I'm up to 120,000 kilometres without any regenerative braking.

--
Xeno

Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On 12/5/2022 5:58 am, Alan wrote:
> On 2022-05-09 8:39 a.m., Andy Burnelli wrote:
>> Xeno wrote:
>>
>>>> You can't test warp on the vehicle (not reliably anyway).
>>>> It has to be tested on a known flat bench (or using known flat tools).
>>>
>>> Or mounted on a brake lathe
>>
>> Agreed. All you need is a long flat edge and feeler gauges as a minimum.
>>
>> I'm all about facts. I'll change my mind in a split second if that's
>> where the facts lead.
>>
>> Let's look at the facts in this discussion between two adults on Usenet.
>>
>> My point is that nobody who says warp (as in potato chip) measures that
>> warp (as in potato chip), where I already know that warp (as in potato
>> chip) isn't what happens when a brake rotor is subject to intense
>> heating &
>> cooling cycles.
>> "High quality brake rotors that pass SAE J2928 Brake Rotor Thermal
>>   Cracking Procedure for Vehicles below 4,540 kg GVWR proves
>>   they don't warp"
>>
>> As I said, intuition is a terrible thing indeed.
>> "Calling it brake rotor warp demonstrates a complete misunderstanding
>>   of the metallurgy and the braking process"
>>
>>> I wasn't saying anything about rebedding at all.
>>
>> OK. But the fact that rebedding works sometimes means that what it fixed
>> wasn't warp (as in potato chip). What it fixed wasn't runout either.
>>
>> What it fixed is the only thing it _could_ fix, which is deposit buildup.
>>
>> Intuition is a terrible thing indeed.
>> "The brake pads and rotors in a street vehicle can't possibly
>>  generate enough heat to warp a brake rotor."
>>
>>>> Almost nobody could machine a warped rotor (as in potato chip) back to
>>>> perfection simply because the amount of metal needed isn't going to be
>>>
>>> Depends on the amount of warp and whether the rotor still meets
>>> minimum specs afterwards. It only takes a very small amount of warp
>>> for the driver to be able to sense it.
>>
>> Agreed.
>> However, any rotor that was subject to enough heat to truly warp it
>> (as in
>> potato chip) was subject to _tremendous_ heat - almost impossible to
>> attain
>> in a passenger vehicle (again, I'm not talking about the space shuttle
>> here).
>> "The heating and cooling that people refer to when discussing  'warped
>> brake rotors' would cause cracking, not warping."
>>
>> There are half a dozen materials rotors are made of though, so we'd
>> have to
>> look up the melting point of each of them to be more precise about
>> melting.
>> 1. cast iron
>> 2. steel
>> 3. stainless steel
>> 4. laminated steel
>> 5. high carbon iron (e.g., Sparta CX3.5)
>> 6. ceramic
>>
>>> The car showed *symptoms* of warp, the rotors, when measured showed
>>> *evidence* of warp. I drove the car, I felt the symptoms, I measured
>>> the rotor warp.
>>
>> I'll leave it at that since I respect your experience.
>>
>> Read this please, though (it's just one random hit of many of course):
>> *What causes warped brake rotors?*
>> <https://ricksfreeautorepairadvice.com/warped-brake-rotors/>
>> "brake rotors DO NOT WARP from  normal driving or even race track use.
>>   Yes, you read that correctly. A typical street vehicle can't possibly
>>   generate enough heat to warp a brake rotor."
>>
>> All the quotes in this one post are from that reference, but I can easily
>> find more because I know what I know and most people are intuitive.
>>
>> Did I mention yet that intuition is a terrible thing?
>>
>>>> I doubt it. Rotors are made of a variety of steels (e.g., motorcycle
>>>> rotors
>>>
>>> I don't, I saw the evidence.
>>
>> Again, I respect your experience.
>> However, you have to respect my knowledge that _reliable_ sources say
>> otherwise and that runout isn't warp (as in potato chip) and that if
>> rebedding worked, it wasn't warp (as in potato chip) after all.
>> "Even if you're traveling straight down the side of a mountain with
>> your brakes applied the entire way. Your brake pads will fade and
>> start to disintegrate long before you come close to heating your
>> rotors enough to soften them to the point where they could possibly warp"
>>
>> I even doubt machining could fix any appreciable warp (as in potato
>> chip), and even if it did, I wouldn't want any rotors from _that_
>> shop. :)
>> "In addition, if your brake system is working properly, it's applying
>> equal pressure to both sides of the rotor which means BOTH SIDES are
>> heating at the same rate. To warp a brake rotor, you must have more
>> heat on one side of the rotor than the other."
>>
>>>> are often stainless steel) but even for the worst quality cast iron
>>>> rotors,
>>>> look up the temperature it takes to melt them.
>>>
>>> Automotive rotors were pretty much all cast iron back in the era
>>> concerned. And the rotor did *melt* at the periphery, as I stated. It
>>> had been damn hot all over but the periphery was clearly melted.
>>
>> I'm not going to argue with you on that as cast iron has a relatively low
>> melting point where our question is can a rotor typically get to that
>> point
>> on a passenger vehicle whose owner suspects his rotor warped (as in
>> potato
>> chip).
>>
>> "To get cast iron hot enough to soften the metal you'd need to generate
>>   almost 2,300�F range. There isn't a factory stock automotive brake
>>   system in the world that's capable of generating that kind of heat.
>>   In fact, you would experience brake pad fade, pad disintegration,
>>   brake fluid boiling and rotor discoloration long before you  reached
>> 1,000�F."
>>
>>>> I'm not saying it's impossible. But I doubt it happens for normal
>>>> passenger
>>>> vehicles (I'm not talking space shuttle stuff or fighter plane stuff).
>>>
>>> Nor am I. I wasn't and never have been an aviation mechanic.
>>
>> The only thing I harp on is I've never met a person who claimed it was
>> "warp" (as in potato chip) who actually measured it, and, worse, the
>> remedy
>> often is something (like rebedding) which couldn't possibly have fixed
>> warp
>> (as in potato chip).
>>
>> Worse than even that, is all the reliable sources say passenger vehicle
>> rotors can't warp (as in potato chip) simply because brakes can't
>> generate
>> enough heat.
>>
>>>> Look it up.
>>>
>>> No need, I saw the evidence directly.
>>
>> I knew what I'd find in brake warp when I just looked it up as I did my
>> research long ago (just as I did with cellphone caused accident rates).
>>
>> Most people work solely on intuition.
>> Humans have the intuition of evolved monkeys.
>>
>> Intuition serves humans well... sometimes.
>> But not always.
>>
>> Read this _one_ reference for a starting point on fixing that intuition.
>> <https://ricksfreeautorepairadvice.com/warped-brake-rotors/>
>>
>> If you don't like it, find another (there are plenty).
>>
>>>> Yes. I know. But did you measure warp (as in potato chip)?
>>>
>>> Yes, I did, with a dial indicator. Definitely warp.
>>
>> "To pass the J2928 rotor test, rotors must withstand at least  150
>> heat cycles on a dynamometer without cracking or showing  any
>> structural or dimensional failure. "
>>
>>>> You can't measure warp without a known straight surface to compare
>>>> against.
>>>> A mic won't measure warp.
>>>> A dial gauge won't measure warp (unless it's a special setup).
>>>
>>> It was a special setup - a brake lathe. Runout and warp shows up very
>>> clearly when the hub and rotor assembly is correctly mounted.
>>
>> Note that the link I am giving you has information from the brake rotor
>> manufacturers who themselves claim that their rotors can't warp (as in
>> potato chip) in passenger vehicles under _any_ circumstances.
>>
>> Raybestos video titled "Rotors Can't Warp":
>> <https://youtu.be/LVRVe1cEBDI>
>>
>>>> HINT: I've never seen anyone who did who said their rotors warped
>>>> when what
>>>> really happened was something else (e.g., runout or pad deposition).
>>>
>>> Depending on the site, runout can be a symptom of warp. You verify it
>>> as warp by checking both sides.
>>
>> I'm not going to harp on the issue other than to repeat my salient
>> points.
>> a. Rotors don't warp (as in potato chip) in passenger vehicles. Period.
>> b. People who _say_ they did, didn't measure warp (as in potato chip).
>> c. The temperatures needed are unattainable in passenger vehicles.
>>
>>>>> If they wouldn't clean up and still remain within specs, they would
>>>>> be replaced, and that could be determined from the measurements.
>>>>
>>>> I seriously doubt an actual warp (as in potato chip) could be
>>>> machined, but
>>>> if it's only slight, then maybe, but what fool would want rotors
>>>> that were
>>>> actually warped (as in potato chip) even after they were machined?
>>>
>>> Well, these days the rule is discard and renew, don't machine.
>>> Procedures have changed.
>>
>> OK. But I can _easily_ find industry references that say rotors can't
>> warp
>> (as in potato chip) simply because they are designed _not_ to warp (as in
>> potato chip), and, because the temperatures to cause warp (as in potato
>> chip) are unattainable.
>
> <https://youtu.be/glIik3KHcOs>
>
> What's that if it's not warp, Arlen?

On 2022-05-11 6:39 p.m., Xeno wrote:
> On 12/5/2022 5:58 am, Alan wrote:
>> On 2022-05-09 8:39 a.m., Andy Burnelli wrote:

>>> OK. But I can _easily_ find industry references that say rotors can't
>>> warp
>>> (as in potato chip) simply because they are designed _not_ to warp
>>> (as in
>>> potato chip), and, because the temperatures to cause warp (as in potato
>>> chip) are unattainable.
>>
>> <https://youtu.be/glIik3KHcOs>
>>
>> What's that if it's not warp, Arlen?
>
> Looks a lot like *warp* to me.  ;-)
>
> I don't think I would be bothered even starting to machine that one -
> binned!
>

The comment that goes with it very nicely matches yours:

'"No such thing as warped brake rotors." I've heard that saying spread
around quite a bit. "What you're experiencing is merely uneven brake
pad transfer." While pad transfer is a phenomenon that exists and one
that I've encountered, I spent 8 years as an automotive technician and
witnessed warped rotors regularly, this case being one of the worst. Be
assured I setup the brake lathe properly and no tricks were done to make
this appear any sort of way. I even double and triple checked my setup
to prove to myself that this rotor was indeed as warped as you are seeing.'

On 12/5/2022 10:33 am, Andy Burnelli wrote:
> sms wrote:
>
>> "Back in the olden days" I kept a spare set of rotors so when I was
>> doing a brake job I didn't have to stop and take the rotors to be
>> machined in the middle of the work. I'd then take the rotors that I
>> removed to be put on a lathe (for free since my relative had a repair
>> shop) and they'd be ready for the next brake job in 25,000 miles or so.
>>
>> But back then discs were thick and heavy and could be machined
>> multiple times before they were too thin. Nowadays rotors are so thin
>> they can usually not be machined even once, but they've also become
>> less expensive (when adjusted for inflation).
>
> I wonder if _anyone_ here realizes _why_ there's a minimum thickness spec?
>
> HINT: It's not what everyone intuits (e.g., it's not for heat dissipation).

It is actually so the rotor can *hold more heat*. It's all about
*heating capacity*, not to cooling. You gain SFA extra surface
dissipation area when you increase the disc thickness. With a thin
(below spec) rotor, you reach brake fade temperatures much more quickly
- it's related to the above point. Also, the thinner the disc, the
greater the likelihood of warping related to strength and heat holding
capacity..

--
Xeno

Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On 12/5/2022 11:44 am, Alan wrote:
> On 2022-05-11 6:39 p.m., Xeno wrote:
>> On 12/5/2022 5:58 am, Alan wrote:
>>> On 2022-05-09 8:39 a.m., Andy Burnelli wrote:
>
>>>> OK. But I can _easily_ find industry references that say rotors
>>>> can't warp
>>>> (as in potato chip) simply because they are designed _not_ to warp
>>>> (as in
>>>> potato chip), and, because the temperatures to cause warp (as in potato
>>>> chip) are unattainable.
>>>
>>> <https://youtu.be/glIik3KHcOs>
>>>
>>> What's that if it's not warp, Arlen?
>>
>> Looks a lot like *warp* to me.  ;-)
>>
>> I don't think I would be bothered even starting to machine that one -
>> binned!
>>
>
> The comment that goes with it very nicely matches yours:
>
> '"No such thing as warped brake rotors."  I've heard that saying spread
> around quite a bit.  "What you're experiencing is merely uneven brake
> pad transfer."  While pad transfer is a phenomenon that exists and one
> that I've encountered, I spent 8 years as an automotive technician and
> witnessed warped rotors regularly, this case being one of the worst.  Be
> assured I setup the brake lathe properly and no tricks were done to make
> this appear any sort of way.  I even double and triple checked my setup
> to prove to myself that this rotor was indeed as warped as you are seeing.'

Yep, as oft stated, I've felt it, seen it, measured it, machined it.

--
Xeno

Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

Xeno wrote:

> That said, my only experience of warped rotors is with the
> non-ventilated variety.

People who think rotors warp also firmly believe the earth is flat.
There is no discernible difference between those two belief systems.

They're both imaginary; they're both strongly held; & they're both wrong.
All the professionals, in this case, Raybestos Training, say so.

*Warped Rotor Myth Training Video, by Raybestos Brand Brakes*
<https://www.facebook.com/RaybestosBrandBrakes/videos/warped-rotor-myth/2174044739282278/>
"Two months ago this vehicle was brought into a shop with a
complaint of pedal pulsation during breaking. The technician
diagnosed the vehicle as warped rotors and replaced the rotors.

Within a short period of time after that replacement,
the vehicle came back again with the same complaint of
pedal pulsation.

Today what we are going to do is dispel the myth of
warped rotors and show you the diagnosis procedure
to help eliminate pedal pulsation.

Many technicians will diagnose pedal pulsation as warped rotors.
Let's dispel that myth right now. *Rotors do not warp.*

*To warp a rotor you physically have to change the*
*metallurgy of that rotor. To change the metallurgy*
*of a rotor, you're running in excess of 2,300 degrees.*

_There is no brake system that runs 2,300 degrees._

Let's take this apart and see what the issues are
that causes the thickness variation.

Typically, every time a vehicle comes into a shop
with a complaint of pedal pulsation, the technician
looks at it as warped rotors. As I mentioned before
*rotors don't warp* but what causes a pedal pulsation
is disk thickness variation.

Disk thickness variation is caused by excessive
lateral runout. Let's take a look at this rotor
and see if we can identify some areas that have
caused this condition.

When we look at the rotor, you can see some black
marks in the rotor. Typically what that is, is
friction transfer from ceramic brake pads.

Ceramic brake pads lay down a coating of friction
material. That has been laid down unevenly which
ends up being thickness variation, causing pedal pulsation.

When you turn the rotor around the other area you
want to look at is the mounting area.

We can see a big rust buildup on the hub area.

As you can see on this hub there's a lot of rust
buildup. This rust can cause excessive lateral
runout which induces thickness variation.

Let's get this cleaned up. Then we can either
replace the rotor or machine it."

Note I'm quoting _reliable_ sources, not bullshit youtube videos
from some teenager in NJ who can't mount a rotor on a lathe straight.

The fact remains that rotors don't warp.
Anyone who believes they do also likely believes the earth is flat.

Most people persist in owning completely imaginary belief systems.
Like I've been saying, intuition is a terrible thing indeed.

Let's stop this nonsense since no amount of facts, logic, and
reason will convince some people the earth isn't flat.

Most people believe their intuition only, & not in any facts.
--
The problem with voting is that the people who own strongly
held imaginary belief systems vastly outnumber the rest of us.

On 2022-05-11 10:17 p.m., Andy Burnelli wrote:
> Xeno wrote:
>
>> That said, my only experience of warped rotors is with the
>> non-ventilated variety.
>
> People who think rotors warp also firmly believe the earth is flat.
> There is no discernible difference between those two belief systems.
>
> They're both imaginary; they're both strongly held; & they're both wrong.
> All the professionals, in this case, Raybestos Training, say so.

Dude:

You've been told by a professional in the field and you've been
presented video evidence.

You're a complete and utter ass.

On 12/5/2022 3:17 pm, Andy Burnelli wrote:
> Xeno wrote:
>
>> That said, my only experience of warped rotors is with the
>> non-ventilated variety.
>
> People who think rotors warp also firmly believe the earth is flat.
> There is no discernible difference between those two belief systems.
>
> They're both imaginary; they're both strongly held; & they're both wrong.
> All the professionals, in this case, Raybestos Training, say so.
>
> *Warped Rotor Myth Training Video, by Raybestos Brand Brakes*
> <https://www.facebook.com/RaybestosBrandBrakes/videos/warped-rotor-myth/2174044739282278/>
>
> "Two months ago this vehicle was brought into a shop with a complaint of
> pedal pulsation during breaking. The technician diagnosed the vehicle as
> warped rotors and replaced the rotors.
> Within a short period of time after that replacement,
> the vehicle came back again with the same complaint of pedal pulsation.
> Today what we are going to do is dispel the myth of warped rotors and
> show you the diagnosis procedure to help eliminate pedal pulsation.
>
> Many technicians will diagnose pedal pulsation as warped rotors. Let's
> dispel that myth right now. *Rotors do not warp.*
> *To warp a rotor you physically have to change the* *metallurgy of that
> rotor. To change the metallurgy*
> *of a rotor, you're running in excess of 2,300 degrees.*
> _There is no brake system that runs 2,300 degrees._
> Let's take this apart and see what the issues are that causes the
> thickness variation.
>
> Typically, every time a vehicle comes into a shop with a complaint of
> pedal pulsation, the technician looks at it as warped rotors. As I
> mentioned before *rotors don't warp* but what causes a pedal pulsation
> is disk thickness variation.
> Disk thickness variation is caused by excessive lateral runout. Let's
> take a look at this rotor
> and see if we can identify some areas that have caused this condition.
> When we look at the rotor, you can see some black marks in the rotor.
> Typically what that is, is friction transfer from ceramic brake pads.
>
> Ceramic brake pads lay down a coating of friction
> material. That has been laid down unevenly which
> ends up being thickness variation, causing pedal pulsation.

You can get thickness variation in a rotor that has *no* pad material
deposition. The most typical cause is the creation of *hard spots* in
the rotor that typically wear *less* than the rest of the rotor. Those
hard spots are created by the rotor being *overheated*.

The problem with hard spots that cause thickness variation is that you
are often unable to *machine* the rotor. What happens when your lathe
tool hits the hard spot is it deflects and rides over the hard spot. In
these cases the rotor can only be *ground*. Of course few brake shops
are equipped to grind rotors and the cost would be prohibitive given the
general cost of a new rotor. The problem anyway with hard spots is that
unless you go deep enough to remove the hardened area, the problem will
recur. Also, by then the rotor will likely be *undersize*.

> When you turn the rotor around the other area you
> want to look at is the mounting area.
> We can see a big rust buildup on the hub area.
>
> As you can see on this hub there's a lot of rust
> buildup. This rust can cause excessive lateral
> runout which induces thickness variation.
> Let's get this cleaned up. Then we can either replace the rotor or
> machine it."
>
> Note I'm quoting _reliable_ sources, not bullshit youtube videos
> from some teenager in NJ who can't mount a rotor on a lathe straight.

I beg to differ. Had you ever done any rotor machining with a decent
brake lathe, you would know that it is very difficult to screw it up.
That disc on one of the videos was quite clearly warped. On another, the
machining process clearly showed the warpage as it cleaned up. I too
have seen this exact same thing very often when I have been machining
rotors.
>
> The fact remains that rotors don't warp.
> Anyone who believes they do also likely believes the earth is flat.
>
> Most people persist in owning completely imaginary belief systems.
> Like I've been saying, intuition is a terrible thing indeed.
>
> Let's stop this nonsense since no amount of facts, logic, and reason
> will convince some people the earth isn't flat.
>
> Most people believe their intuition only, & not in any facts.

I believe in what I see, what I feel, what I measure, etc. And I have
seen warped rotors, I have cleaned up and put back into service lightly
warped rotors and I have rejected rotors too far gone to clean up. And
yes, I have seen all the other types of rotor faults too and, what's
more, I can differentiate.

--
Xeno

Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On 2022-05-12 12:23 a.m., Xeno wrote:
> On 12/5/2022 3:17 pm, Andy Burnelli wrote:
>> Xeno wrote:
>>
>>> That said, my only experience of warped rotors is with the
>>> non-ventilated variety.
>>
>> People who think rotors warp also firmly believe the earth is flat.
>> There is no discernible difference between those two belief systems.
>>
>> They're both imaginary; they're both strongly held; & they're both wrong.
>> All the professionals, in this case, Raybestos Training, say so.
>>
>> *Warped Rotor Myth Training Video, by Raybestos Brand Brakes*
>> <https://www.facebook.com/RaybestosBrandBrakes/videos/warped-rotor-myth/2174044739282278/>
>>
>> "Two months ago this vehicle was brought into a shop with a complaint
>> of pedal pulsation during breaking. The technician diagnosed the
>> vehicle as warped rotors and replaced the rotors.
>> Within a short period of time after that replacement,
>> the vehicle came back again with the same complaint of pedal pulsation.
>> Today what we are going to do is dispel the myth of warped rotors and
>> show you the diagnosis procedure to help eliminate pedal pulsation.
>>
>> Many technicians will diagnose pedal pulsation as warped rotors. Let's
>> dispel that myth right now. *Rotors do not warp.*
>> *To warp a rotor you physically have to change the* *metallurgy of
>> that rotor. To change the metallurgy*
>> *of a rotor, you're running in excess of 2,300 degrees.*
>> _There is no brake system that runs 2,300 degrees._
>> Let's take this apart and see what the issues are that causes the
>> thickness variation.
>>
>> Typically, every time a vehicle comes into a shop with a complaint of
>> pedal pulsation, the technician looks at it as warped rotors. As I
>> mentioned before *rotors don't warp* but what causes a pedal pulsation
>> is disk thickness variation.
>> Disk thickness variation is caused by excessive lateral runout. Let's
>> take a look at this rotor
>> and see if we can identify some areas that have caused this condition.
>> When we look at the rotor, you can see some black marks in the rotor.
>> Typically what that is, is friction transfer from ceramic brake pads.
>>
>> Ceramic brake pads lay down a coating of friction
>> material. That has been laid down unevenly which
>> ends up being thickness variation, causing pedal pulsation.
>
> You can get thickness variation in a rotor that has *no* pad material
> deposition. The most typical cause is the creation of *hard spots* in
> the rotor that typically wear *less* than the rest of the rotor. Those
> hard spots are created by the rotor being *overheated*.
>
> The problem with hard spots that cause thickness variation is that you
> are often unable to *machine* the rotor. What happens when your lathe
> tool hits the hard spot is it deflects and rides over the hard spot. In
> these cases the rotor can only be *ground*. Of course few brake shops
> are equipped to grind rotors and the cost would be prohibitive given the
> general cost of a new rotor. The problem anyway with hard spots is that
> unless you go deep enough to remove the hardened area, the problem will
> recur. Also, by then the rotor will likely be *undersize*.
>
>
>> When you turn the rotor around the other area you
>> want to look at is the mounting area.
>> We can see a big rust buildup on the hub area.
>>
>> As you can see on this hub there's a lot of rust
>> buildup. This rust can cause excessive lateral
>> runout which induces thickness variation.
>> Let's get this cleaned up. Then we can either replace the rotor or
>> machine it."
>>
>> Note I'm quoting _reliable_ sources, not bullshit youtube videos
>> from some teenager in NJ who can't mount a rotor on a lathe straight.
>
> I beg to differ. Had you ever done any rotor machining with a decent
> brake lathe, you would know that it is very difficult to screw it up.
> That disc on one of the videos was quite clearly warped. On another, the
> machining process clearly showed the warpage as it cleaned up. I too
> have seen this exact same thing very often when I have been machining
> rotors.
>>
>> The fact remains that rotors don't warp.
>> Anyone who believes they do also likely believes the earth is flat.
>>
>> Most people persist in owning completely imaginary belief systems.
>> Like I've been saying, intuition is a terrible thing indeed.
>>
>> Let's stop this nonsense since no amount of facts, logic, and reason
>> will convince some people the earth isn't flat.
>>
>> Most people believe their intuition only, & not in any facts.
>
> I believe in what I see, what I feel, what I measure, etc. And I have
> seen warped rotors, I have cleaned up and put back into service lightly
> warped rotors and I have rejected rotors too far gone to clean up. And
> yes, I have seen all the other types of rotor faults too and, what's
> more, I can differentiate.
>

And Arlen will continue to insist that his "education" (which he won't
substantiate) trumps your real-world experience and knowledge.

Alan <nuh-uh@nope.com> wrote:
> On 2022-05-12 12:23 a.m., Xeno wrote:
>> On 12/5/2022 3:17 pm, Andy Burnelli wrote:
>>> Xeno wrote:
>>>
>>>> That said, my only experience of warped rotors is with the
>>>> non-ventilated variety.
>>>
>>> People who think rotors warp also firmly believe the earth is flat.
>>> There is no discernible difference between those two belief systems.
>>>
>>> They're both imaginary; they're both strongly held; & they're both wrong.
>>> All the professionals, in this case, Raybestos Training, say so.
>>>
>>> *Warped Rotor Myth Training Video, by Raybestos Brand Brakes*
>>> <https://www.facebook.com/RaybestosBrandBrakes/videos/warped-rotor-myth/2174044739282278/>
>>>
>>>
>>> "Two months ago this vehicle was brought into a shop with a complaint
>>> of pedal pulsation during breaking. The technician diagnosed the
>>> vehicle as warped rotors and replaced the rotors.
>>> Within a short period of time after that replacement,
>>> the vehicle came back again with the same complaint of pedal pulsation.
>>> Today what we are going to do is dispel the myth of warped rotors and
>>> show you the diagnosis procedure to help eliminate pedal pulsation.
>>>
>>> Many technicians will diagnose pedal pulsation as warped rotors. Let's
>>> dispel that myth right now. *Rotors do not warp.*
>>> *To warp a rotor you physically have to change the* *metallurgy of
>>> that rotor. To change the metallurgy*
>>> *of a rotor, you're running in excess of 2,300 degrees.*
>>> _There is no brake system that runs 2,300 degrees._
>>> Let's take this apart and see what the issues are that causes the
>>> thickness variation.
>>>
>>> Typically, every time a vehicle comes into a shop with a complaint of
>>> pedal pulsation, the technician looks at it as warped rotors. As I
>>> mentioned before *rotors don't warp* but what causes a pedal pulsation
>>> is disk thickness variation.
>>> Disk thickness variation is caused by excessive lateral runout. Let's
>>> take a look at this rotor
>>> and see if we can identify some areas that have caused this condition.
>>> When we look at the rotor, you can see some black marks in the rotor.
>>> Typically what that is, is friction transfer from ceramic brake pads.
>>>
>>> Ceramic brake pads lay down a coating of friction
>>> material. That has been laid down unevenly which
>>> ends up being thickness variation, causing pedal pulsation.
>>
>> You can get thickness variation in a rotor that has *no* pad material
>> deposition. The most typical cause is the creation of *hard spots* in
>> the rotor that typically wear *less* than the rest of the rotor. Those
>> hard spots are created by the rotor being *overheated*.
>>
>> The problem with hard spots that cause thickness variation is that you
>> are often unable to *machine* the rotor. What happens when your lathe
>> tool hits the hard spot is it deflects and rides over the hard spot. In
>> these cases the rotor can only be *ground*. Of course few brake shops
>> are equipped to grind rotors and the cost would be prohibitive given the
>> general cost of a new rotor. The problem anyway with hard spots is that
>> unless you go deep enough to remove the hardened area, the problem will
>> recur. Also, by then the rotor will likely be *undersize*.
>>
>>
>>> When you turn the rotor around the other area you
>>> want to look at is the mounting area.
>>> We can see a big rust buildup on the hub area.
>>>
>>> As you can see on this hub there's a lot of rust
>>> buildup. This rust can cause excessive lateral
>>> runout which induces thickness variation.
>>> Let's get this cleaned up. Then we can either replace the rotor or
>>> machine it."
>>>
>>> Note I'm quoting _reliable_ sources, not bullshit youtube videos
>>> from some teenager in NJ who can't mount a rotor on a lathe straight.
>>
>> I beg to differ. Had you ever done any rotor machining with a decent
>> brake lathe, you would know that it is very difficult to screw it up.
>> That disc on one of the videos was quite clearly warped. On another, the
>> machining process clearly showed the warpage as it cleaned up. I too
>> have seen this exact same thing very often when I have been machining
>> rotors.
>>>
>>> The fact remains that rotors don't warp.
>>> Anyone who believes they do also likely believes the earth is flat.
>>>
>>> Most people persist in owning completely imaginary belief systems.
>>> Like I've been saying, intuition is a terrible thing indeed.
>>>
>>> Let's stop this nonsense since no amount of facts, logic, and reason
>>> will convince some people the earth isn't flat.
>>>
>>> Most people believe their intuition only, & not in any facts.
>>
>> I believe in what I see, what I feel, what I measure, etc. And I have
>> seen warped rotors, I have cleaned up and put back into service lightly
>> warped rotors and I have rejected rotors too far gone to clean up. And
>> yes, I have seen all the other types of rotor faults too and, what's
>> more, I can differentiate.
>>
>
> And Arlen will continue to insist that his "education" (which he won't
> substantiate) trumps your real-world experience and knowledge.
>

Maybe we’ll get to see some more of his book pictures.

On Wed, 11 May 2022 21:49:37 +0100, Andy Burnelli <spam@nospam.com> wrote:

>Vic Smith wrote:
>
snip
>> You'll probably find this study interesting:
>> https://link.springer.com/article/10.1007/s11665-012-0397-7#article-info
>> Let me know what you think of it.
>
>Nice catch. Right down my line.
>
snip
> At that point I started to read how they ran their experiment,
> but let's not summarize that here as I don't see anything wrong
> with what they did (nor am I'm qualified to critique them).
Here's what I took from the study.
"In particular, brake judder has been an important issue in vehicle comfort in recent
years, and various methodologies for reducing this low-frequency vibration have been used
(Ref 6-8). It is known that disk warping or uneven disk thicknesses induce pulsation during
brake applications."
Also noteworthy to me are the affiliations of the authors:
Department of Materials Science and Engineering, Korea University.
R&D Division, Hyundai Motor Company and Kia Motors Corporation.

I recall you asked for an example of a reputable cite stating warped rotors exist, and this
cite certainly qualifies.
As an aside, I'm not suggesting that warped rotors are a common occurrence. I've only
encountered it once. No doubt warp is a catchall for pad deposition and hard spots of
rotors. But it does occur. My opinion is it is a manufacturing defect caused by improper
heat treating during production of the rotor. Having spent 3-4 years as a heat treater in
a mass production environment I'm aware there are many ways that process can be fubarred.
I'm not surprised. My two cents.

Xeno wrote:

> I believe in what I see, what I feel, what I measure, etc. And I have
> seen warped rotors, I have cleaned up and put back into service lightly
> warped rotors and I have rejected rotors too far gone to clean up. And
> yes, I have seen all the other types of rotor faults too and, what's
> more, I can differentiate.

Hi Xeno,
Let's cut our losses as you will _never_ read any reference I've provided.

I provided, what, oh, maybe about a dozen reliable references that back up
my point of view, and you provided, oh, um, what? Zero, right?

You think I didn't know that was going to happen, oh, maybe a decade ago?
There's a reason I said that we own the intuition of monkeys, Xeno.

And there's a reason I said that this intuition is a terrible thing indeed.
People who trust only in their intuition are only right by pure chance.

It's people who trust in facts who are right more often than they're wrong.
And you don't want to see any facts (you didn't even _read_ them, in fact).

That means it's impossible to carry on an adult conversation with you on
this topic. It's like asking someone to stop believing in the Easter Bunny.

Let's just leave it at that because I can provide ten thousand factual
references that the earth isn't flat and there will _still_ be people like
you and Steve and Alan Baker who will emphatically claim it _is_ flat.

Not only that it's flat, but they'll find some 30-second YouTube video of a
twelve year old kid in NJ who, with just a yardstick, "proved" it's flat.

So let's cut our losses.
You think the earth is flat, and you have Alan Baker on your side.
Steve too.

All I have on my side is every reputable brake expert in the industry.
I won't provide you with any more facts because you don't want to see them.
--
HINT: Even the iKooks have long ago plonked Alan Baker, so for you to agree
with him on everything he says is not looking to good for you, Xeno.

On 12/5/2022 7:37 pm, Andy Burnelli wrote:
> Xeno wrote:
>
>> I believe in what I see, what I feel, what I measure, etc. And I have
>> seen warped rotors, I have cleaned up and put back into service
>> lightly warped rotors and I have rejected rotors too far gone to clean
>> up. And yes, I have seen all the other types of rotor faults too and,
>> what's more, I can differentiate.
>
> Hi Xeno,
> Let's cut our losses as you will _never_ read any reference I've provided.
>
> I provided, what, oh, maybe about a dozen reliable references that back up
> my point of view, and you provided, oh, um, what? Zero, right?
>
> You think I didn't know that was going to happen, oh, maybe a decade ago?
> There's a reason I said that we own the intuition of monkeys, Xeno.
>
> And there's a reason I said that this intuition is a terrible thing indeed.
> People who trust only in their intuition are only right by pure chance.
>
> It's people who trust in facts who are right more often than they're wrong.
> And you don't want to see any facts (you didn't even _read_ them, in fact).
>
> That means it's impossible to carry on an adult conversation with you on
> this topic. It's like asking someone to stop believing in the Easter Bunny.
>
> Let's just leave it at that because I can provide ten thousand factual
> references that the earth isn't flat and there will _still_ be people like
> you and Steve and Alan Baker who will emphatically claim it _is_ flat.
>
> Not only that it's flat, but they'll find some 30-second YouTube video of a
> twelve year old kid in NJ who, with just a yardstick, "proved" it's flat.
>
> So let's cut our losses.
> You think the earth is flat, and you have Alan Baker on your side.
> Steve too.
>
> All I have on my side is every reputable brake expert in the industry.
> I won't provide you with any more facts because you don't want to see them.

I have real world experience with disc brakes on my side, that's enough!

--
Xeno

Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On 12/5/2022 7:06 pm, Vic Smith wrote:
> On Wed, 11 May 2022 21:49:37 +0100, Andy Burnelli <spam@nospam.com> wrote:
>
>> Vic Smith wrote:
>>
> snip
>>> You'll probably find this study interesting:
>>> https://link.springer.com/article/10.1007/s11665-012-0397-7#article-info
>>> Let me know what you think of it.
>>
>> Nice catch. Right down my line.
>>
> snip
>> At that point I started to read how they ran their experiment,
>> but let's not summarize that here as I don't see anything wrong
>> with what they did (nor am I'm qualified to critique them).
>
> Here's what I took from the study.
> "In particular, brake judder has been an important issue in vehicle comfort in recent
> years, and various methodologies for reducing this low-frequency vibration have been used
> (Ref 6-8). It is known that disk warping or uneven disk thicknesses induce pulsation during
> brake applications."

And it also can cause shimmy without pulsations or judder. That I have
definitely experienced and on my own car.

> Also noteworthy to me are the affiliations of the authors:
> Department of Materials Science and Engineering, Korea University.
> R&D Division, Hyundai Motor Company and Kia Motors Corporation.
>
> I recall you asked for an example of a reputable cite stating warped rotors exist, and this
> cite certainly qualifies.
> As an aside, I'm not suggesting that warped rotors are a common occurrence. I've only
> encountered it once. No doubt warp is a catchall for pad deposition and hard spots of
> rotors. But it does occur. My opinion is it is a manufacturing defect caused by improper

A lot of people, when doing diagnosis, cannot differentiate the
symptoms. At the end of the day, the process of *measuring* and
*machining* clears up beyond any shadow of doubt as to what the problem is.

> heat treating during production of the rotor. Having spent 3-4 years as a heat treater in
> a mass production environment I'm aware there are many ways that process can be fubarred.
> I'm not surprised. My two cents.

--
Xeno

Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

Vic Smith wrote:

> Here's what I took from the study.

You do know that cast gray iron _melts_ at about 2,300�F, right?
<https://ricksfreeautorepairadvice.com/warped-brake-rotors/>
"To get cast iron hot enough to soften the metal you'd need to generate
almost 2,300�F range. There isn't a factory stock automotive brake
system in the world that's capable of generating that kind of heat.
In fact, you would experience brake pad fade, pad disintegration,
brake fluid boiling and rotor discoloration long before you
reached 1,000�F."

And, let's be clear about the boiling point of brake fluid, Vic.
<https://www.dixcel.co.jp/en/subcontent/literature/literature02.html>
DOT 3 >401�F (new) & 284�F (1-2 years old)
DOT 4 >446�F (new) & 311�F (1-2 years old)
DOT 5.1 >500�F (new) & 356�F (1-2 years old)
DOT 5 >500�F (new) & 356�F (1-2 years old)

Having said that, you do realize the test disks used in that experiment
were not "normal" in that the prior heat treatment was for five & ten hours
at 1,076�F and then furnace cooled to 572�F at the rate of 104�F per hour
for about five more hours, and then air cooled to room temperature for a
few more hours _before_ testing on the dynamometer, right?

*How often do _your_ brake rotors spend ten hours at a thousand degrees?*

They tested those cast iron rotors under those rather extreme conditions
because they were scientists & engineers who were studying the effects of
various manufacturing conditions for improving cast materials, and because
they were interested in crafting what they called a "prescreening process"
for disk selection at the early stages of brake system development.

It's almost certainly good science, but it's not a real-world test, Vic.
HINT: _A brake system would be marshmallows under those conditions._
--
*The Effect of Residual Stress on the Distortion of Gray Iron Brake Disks*
<https://link.springer.com/article/10.1007/s11665-012-0397-7#article-info>

On 5/11/2022 6:29 PM, Xeno wrote:
> On 12/5/2022 6:01 am, Alan wrote:

>> <https://www.youtube.com/watch?v=DiuwzN2mQuA&t=122s>
>
> Yep, done that, seen the warp, many, many times!
>
> I liked the way he did that final non-directional finish. I used to do
> it the hard way, that looked easy in comparison.

Good video

Andy Burnelli/Arlen Holder/Dean Hoffman/Nil/Robin Goodfellow/more is
wrong of course™.

Those look like pretty thick rotors. The warping had to be pretty minor
in order to machine them flat. Most of the rotors these days are too
thin to machine and are just replaced as part of brake job.

There is one train of thought that turning sufficiently thick, flat,
non-warped, rotors, is unnecessary and that after a short while the pads
will break in to match the minor imperfections in the rotor, with just a
little extra wear on the pads. "If your rotor surface is smooth there is
generally no need to have them turned. If, however, you have warping, or
rough spots they should be turned, or replaced if need be. This is
easily detected if you have a solid, non-pulsing braking action when you
press down on the pedal,"
<https://www.carsdirect.com/car-repair/when-should-you-turn-brake-rotors>.

sms wrote:

> <https://www.carsdirect.com/car-repair/when-should-you-turn-brake-rotors>.

People like Steve are no different than people who believe the earth is flat.
Steve actually _believes_ what he writes.... and yet...
And yet... and yet... Steve doesn't even _read_ what the experts say about it.

As a result, Steve will _never_ (ever!) find a reputable expert to back up his
claims that the earth is, dammit, flat.

But... he can _always_ find a salesperson selling bullshit to back him up.
Which is what Steve did in this thread (and with his four URLs):
<https://www.cartalk.com/blogs/dear-car-talk/warped-brake-discs-are-bad-news>
<https://brakeexperts.com/what-causes-brake-rotors-to-warp/>
<https://www.sandiegouniontribune.com/cars/click-and-clack/story/2019-05-02/warped-rotors-give-this-pony-the-shakes>
<https://www.carsdirect.com/car-repair/when-should-you-turn-brake-rotors>.

Notice Steve can't find even a _single_ expert backing up his claims
that the earth is flat simply because he found people who said so.

Below is what Steve is completely unaware of (it's from _all_ the experts).
==================
*Warped Rotor Myth Training Video, by Raybestos Brand Brakes*
<https://www.facebook.com/RaybestosBrandBrakes/videos/warped-rotor-myth/2174044739282278/>
Many technicians will diagnose pedal pulsation as warped rotors.
Let's dispel that myth right now. *Rotors do not warp.*

*To warp a rotor you physically have to change the*
*metallurgy of that rotor. To change the metallurgy*
*of a rotor, you're running in excess of 2,300 degrees.*

_There is no brake system that runs 2,300 degrees._
==================
<https://ricksfreeautorepairadvice.com/warped-brake-rotors/>
"To get cast iron hot enough to soften the metal you'd need to generate
almost 2,300�F range. There isn't a factory stock automotive brake
system in the world that's capable of generating that kind of heat.
In fact, you would experience brake pad fade, pad disintegration,
brake fluid boiling and rotor discoloration long before you
reached 1,000�F."
==================
Let's be clear we're "mostly" talking cast iron rotors here:
1. cast iron (2,300�F)
2. steel
3. stainless steel
4. laminated steel
5. high carbon iron (e.g., Sparta CX3.5)
6. ceramic

And, let's be clear about the boiling point of brake fluid.
<https://www.dixcel.co.jp/en/subcontent/literature/literature02.html>
DOT 3 >401�F (new) & 284�F (1-2 years old)
DOT 4 >446�F (new) & 311�F (1-2 years old)
DOT 5.1 >500�F (new) & 356�F (1-2 years old)
DOT 5 >500�F (new) & 356�F (1-2 years old)
==================
*Stop the "Warped" Rotors Myth and Service Brakes the Right Way*
<https://www.brakeandfrontend.com/warped-rotors-myth/>
Rotors are cast in extreme heat at three to five times greater
than the most aggressive braking situation. Physically 'warping'
a rotor would require a similar application of extreme heat,
which is impossible."
==================
*The 'Warped' Brake Disc & Other Myths of the Braking System*
<https://centricparts.com/getmedia/bd69395a-b65c-481d-93f7-b26b1bd0638d/Centric_and_APC_Technical_Whitepaper_B1-Warped-Brake-Disc-8-2018_1.pdf>
<https://www.ipdusa.com/Articles/528/The-Warped-Brake-Disc-and-Other-Myths-of-the-Braking-System>
"In more than 40 years of professional racing, including the
Shelby/Ford GT 40s - one of the most intense brake development
programs in history - I have never seen a warped brake disc."
==================
<https://www.brakeandfrontend.com/brake-rotors-dont-warp-the-earth-is-not-flat/>
"By declaring a customer's brake pedal pulsation complaint is caused
by warped rotors is like saying the earth is flat. Both are cases where
the observation of the person is based on a tiny piece of evidence
that is false in nature and application."
==================
<https://www.crossdrilledrotors.ca/blog/part-one-rotors-dont-warp>
"Brake rotors do not warp from heat, even when driven by the
most aggressive traffic officer."
==================
*The Mystery of Warped Brake Rotors*
<https://trade.mechanic.com.au/news/solved-the-mystery-of-warped-brake-rotors>
"Contrary to popular belief, brake rotors, and especially brake rotors
supplied by a reputable manufacturer such as DBA don't warp, no matter
how aggressively a vehicle is driven. Yet, as we know, brake pedal
pulsation caused by out-of-true brake rotors is a fairly common problem
that is almost invariably attributed to warped rotors, which is almost
invariably confirmed by excessive amounts of rotor run out that is easy
to "prove" with a dial gauge."
==================
*Why Do Brake Rotors Warp?*
<https://www.buybrakes.com/help/why-do-brake-rotors-warp/>
"The thing is, rotors don't actually permanently warp. It may feel that
way when braking, but what really happens is that they become irregular
due to excessive lateral run out of the rotor face. You can feel through
the brake pedal as little as .002" of run out. This amount of run out is
far smaller than you can see. In other words, rotors always remain true,
but they can wear out irregularly for several reasons."
1. Lug torque
2. Hub rust
3. Hub runout
==================
*Brake Rotors Warp From Heat -- Myth Busted*
<https://www.hansonsubaru.com/service/information/brake-myths.htm>
"there's simply no way that a brake rotor can get hot enough to warp
or deform on an ordinary passenger car."
==================
*Nuts & Bolts: Warped Rotor Myth*
<https://www.motortrend.com/how-to/1808-nuts-and-bolts-warped-rotor-myth/>
"It's exceedingly rare to actually warp a rotor. Instead, the cause
of the shudder you feel through the pedal is an uneven buildup
of brake pad material on the rotor itself. As little as 0.0004 inch
can be felt through the pedal & 0.001 inch can be downright annoying"
==================
**Everything You Need to Know About High-Tech Rotors**
<https://www.motortrend.com/how-to/understanding-disc-brake-rotors/>
"The most persistent myth about rotors is that they warp. It takes a
lot of heat, the kind of heat used in the casting process, to actually
warp a rotor. The two common problems that cause pedal pulsation are
lateral run-out and disc thickness variation. Lateral run-out is
typically caused by run-out from the hub face, wheel bearing, uneven
lug nut torque, or a buildup of rust and corrosion between wheel and hub.
Disc thickness variation is most often caused by excess pad transfer,
the very thin layer of pad material that bonds to the rotor surface,
and uneven wear from an improperly mounted caliper. "
==================
*Warped Brake Rotors - Vibrating Reality or Internet Myth?*
<https://blog.fcpeuro.com/warped-brake-rotors-vibrating-reality-or-internet-myth>
"Traditionally, this was blamed on warped rotors, and the prescription
was to either get the rotors machined or to replace the rotors.
Technically this wasn't wrong, but it's not completely right either.
To understand what is going on, lets examine how the brake pads
and rotors interact. It's not as simple as it seems on the surface,
and relies on complex interaction between friction materials.
Technically yes, the rotor is warped because the buildup of pad deposits
is a few thousandths of an inch thick. To restore proper smooth braking
performance, the uneven deposits need to be removed, and a fresh uniform
layer of friction material needs to be laid down."
==================
*Stop the "Warped" Rotors Myth and Service Brakes the Right Way*
<https://www.brakeandfrontend.com/warped-rotors-myth/>
"Myths take hold �because either A) they seem completely logical or
B) they are so often repeated that they just become common knowledge.
The warped rotor myth is a little bit of both. A rotor that
contributed to a pulsation condition certainly appears 'warped.'
Plus, everyone says it - even technicians that know the rotor isn't
really warped will say it as shorthand. Rotors are cast in extreme heat
at three to five times greater than the most aggressive braking
situation. Physically 'warping' a rotor would require a similar
application of extreme heat, which is impossible."
==================
*Six Brake Rotor Myths Debunked*
<https://www.onallcylinders.com/2017/05/19/6-biggest-brake-rotor-myths-debunked/>
Brake Rotors Warp - Rotors don't warp.
Back in the 1970s, in what was probably a scene right out of the
movie Dazed and Confused, someone came up with a theory about
brake-rotor "warping," and it totally stuck. Why? Probably because,
in layman's terms, it makes sense.
But then real life happens and this faulty explanation doesn't
hold up to scientific scrutiny.
What is often described as "warping" is actually the presence of
two separate phenomena that can happen in isolation or in combination
with each other, and neither has anything to do with warping.
These phenomena are:
a. Brake torque variation (BTV), and
b. Disc thickness variation (DTV)
==================
*The myth of warped brake discs*
<https://alconkits.com/technical-info/brake-tech/56-the-myth-of-warped-brake-discs>
"Have you ever heard someone say they had warped brake discs?
Typically someone had the discs resurfaced to cure the problem
and after a relatively short time the roughness or vibration came back.
In almost every case, this problem is not caused by a warped discs,
but that the brake pad material transferred unevenly to the surface
of the disc. This uneven deposition results in thickness variation
or run-out due to hot spotting that occurred at elevated temperatures."
==================
<https://ricksfreeautorepairadvice.com/warped-brake-rotors/>
"Calling it brake rotor warp demonstrates a complete misunderstanding
of the metallurgy and the braking process"
==================
--
People like Steve are no different than people who believe the earth is flat.

On 2022-05-12 4:01 p.m., Andy Burnelli wrote:
> sms wrote:
>
>> <https://www.carsdirect.com/car-repair/when-should-you-turn-brake-rotors>.
>>
>
> People like Steve are no different than people who believe the earth is
> flat.
> Steve actually _believes_ what he writes.... and yet... And yet... and
> yet... Steve doesn't even _read_ what the experts say about it.
>
> As a result, Steve will _never_ (ever!) find a reputable expert to back
> up his
> claims that the earth is, dammit, flat.
>
> But... he can _always_ find a salesperson selling bullshit to back him up.
> Which is what Steve did in this thread (and with his four URLs):
> <https://www.cartalk.com/blogs/dear-car-talk/warped-brake-discs-are-bad-news>
>
> <https://brakeexperts.com/what-causes-brake-rotors-to-warp/>
> <https://www.sandiegouniontribune.com/cars/click-and-clack/story/2019-05-02/warped-rotors-give-this-pony-the-shakes>
>
> <https://www.carsdirect.com/car-repair/when-should-you-turn-brake-rotors>.
>
> Notice Steve can't find even a _single_ expert backing up his claims
> that the earth is flat simply because he found people who said so.

Empiricism trumps your bullshit, Arlen:

'In the past people here have said that rotors don't "warp". That
shaking or shuddering during braking is caused by brake pad deposits.
This is on my lathe right now. You can see the spots where the bit is
not even touching the rotor. Definitely NOT pad deposits. The bits are
missing the rotor on opposite sides like you would think it would if a
rotor was warped. Thoughts?'

<https://bobistheoilguy.com/forums/threads/warped-rotor-pics.309555/>

Xeno wrote:

> I have real world experience with disc brakes on my side, that's enough!

You didn't have to tell me that.
I knew it.

Your real-world experience is very helpful sometimes.
As it was with the tire wear on mountain roads.

I appreciate that.
I won't delve further on the brake rotor warp issue.
--
My only caution is that you side with Alan Baker which doesn't bode well
for your ability to discern logic (nobody even responds to Alan but Steve).

On 2022-05-12 5:12 p.m., Andy Burnelli wrote:
> Xeno wrote:
>
>> I have real world experience with disc brakes on my side, that's enough!
>
> You didn't have to tell me that.
> I knew it.
>
> Your real-world experience is very helpful sometimes.
> As it was with the tire wear on mountain roads.
>
> I appreciate that.
> I won't delve further on the brake rotor warp issue.

Because you lack the integrity to admit you were wrong.

On 5/12/2022 4:37 AM, Andy Burnelli wrote:
> Xeno wrote:
>
>> I believe in what I see, what I feel, what I measure, etc.
>> And I have seen warped rotors, I have cleaned up and put
>> back into service lightly warped rotors and I have
>> rejected rotors too far gone to clean up. And yes, I have
>> seen all the other types of rotor faults too and, what's
>> more, I can differentiate.
>
> Hi Xeno,
> Let's cut our losses as you will _never_ read any reference
> I've provided.
>
> I provided, what, oh, maybe about a dozen reliable
> references that back up
> my point of view, and you provided, oh, um, what? Zero, right?
>
> You think I didn't know that was going to happen, oh, maybe
> a decade ago?
> There's a reason I said that we own the intuition of
> monkeys, Xeno.
>
> And there's a reason I said that this intuition is a
> terrible thing indeed.
> People who trust only in their intuition are only right by
> pure chance.
>
> It's people who trust in facts who are right more often than
> they're wrong.
> And you don't want to see any facts (you didn't even _read_
> them, in fact).
>
> That means it's impossible to carry on an adult conversation
> with you on
> this topic. It's like asking someone to stop believing in
> the Easter Bunny.
>
> Let's just leave it at that because I can provide ten
> thousand factual
> references that the earth isn't flat and there will _still_
> be people like
> you and Steve and Alan Baker who will emphatically claim it
> _is_ flat.
>
> Not only that it's flat, but they'll find some 30-second
> YouTube video of a
> twelve year old kid in NJ who, with just a yardstick,
> "proved" it's flat.
>
> So let's cut our losses.
> You think the earth is flat, and you have Alan Baker on your
> side.
> Steve too.
>
> All I have on my side is every reputable brake expert in the
> industry.
> I won't provide you with any more facts because you don't
> want to see them.

f you're so certain about that why not offer to pay parts
and service charges for a warped brake rotor?

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

On 2022-05-12 5:27 p.m., AMuzi wrote:
> On 5/12/2022 4:37 AM, Andy Burnelli wrote:
>> Xeno wrote:
>>
>>> I believe in what I see, what I feel, what I measure, etc.
>>> And I have seen warped rotors, I have cleaned up and put
>>> back into service lightly warped rotors and I have
>>> rejected rotors too far gone to clean up. And yes, I have
>>> seen all the other types of rotor faults too and, what's
>>> more, I can differentiate.
>>
>> Hi Xeno,
>> Let's cut our losses as you will _never_ read any reference
>> I've provided.
>>
>> I provided, what, oh, maybe about a dozen reliable
>> references that back up
>> my point of view, and you provided, oh, um, what? Zero, right?
>>
>> You think I didn't know that was going to happen, oh, maybe
>> a decade ago?
>> There's a reason I said that we own the intuition of
>> monkeys, Xeno.
>>
>> And there's a reason I said that this intuition is a
>> terrible thing indeed.
>> People who trust only in their intuition are only right by
>> pure chance.
>>
>> It's people who trust in facts who are right more often than
>> they're wrong.
>> And you don't want to see any facts (you didn't even _read_
>> them, in fact).
>>
>> That means it's impossible to carry on an adult conversation
>> with you on
>> this topic. It's like asking someone to stop believing in
>> the Easter Bunny.
>>
>> Let's just leave it at that because I can provide ten
>> thousand factual
>> references that the earth isn't flat and there will _still_
>> be people like
>> you and Steve and Alan Baker who will emphatically claim it
>> _is_ flat.
>>
>> Not only that it's flat, but they'll find some 30-second
>> YouTube video of a
>> twelve year old kid in NJ who, with just a yardstick,
>> "proved" it's flat.
>>
>> So let's cut our losses.
>> You think the earth is flat, and you have Alan Baker on your
>> side.
>> Steve too.
>>
>> All I have on my side is every reputable brake expert in the
>> industry.

Where "reputable" is redefined as "agrees with me".

>> I won't provide you with any more facts because you don't
>> want to see them.
>
> f you're so certain about that why not offer to pay parts and service
> charges for a warped brake rotor?

Very good question.

:-)

AMuzi wrote:

> If you're so certain about that why not offer to pay parts
> and service charges for a warped brake rotor?

If that's supposed to be a question, I readily admit I don't know what
you're asking.

Can you please rephrase the question so that I can understand what you're
asking me to respond to?

Thanks!