On 9/5/2022 1:43 am, Andy Burnelli wrote:
> NY wrote:
>
>> I was quite surprised that discs would get *that* hot, and that brake
>> pads would withstand contact with red-hot metal.
>
> Regarding brake rotor warp (as in "potato chip"), that (almost) never
> happens on rotors that didn't come out of the factory already warped.

When I was doing a lot of brake repairs, and operating a brake lathe, I
came across many warped rotors. One is required, after all, to check
discs and drums for wear, distortion, runout and the like. In my
experience, there were two possible factors involved in warped discs -
overheating of rotors and incorrect sequence tightening of wheel nuts.
Or simply overtightening. And, no, they didn't come out of the factory
already warped. The worst for warping through overtightening were the
integral hub and disc rotor. The separate rotor tended to be more prone
to warping through overheating. Note too, a warped disc will evince
different symptoms to a disc suffering pad deposition. The first car I
owned that suffered from disc warping was a MkII 240 Ford Cortina but I
drove that thing like a rally car back in the days.
>
> Regarding temperatures, the _melting_ point is (almost) impossible to reach
> in braking operations given the type of vehicles we're all talking about.

I managed to reach it on one car I owned back in the early days of disc
brakes. Admittedly, the rotor was sub par on the thickness hence a
reduced heat capacity. It sure melted at the periphery though and was
showing signs of heat stress all over - it was black and blue. ;-)
>
> Regarding pad deposition, it's hard to believe, (even for me), but it takes
> only a small amount (almost impossible to measure directly) of "bump" of
> collected pad chemical "footprint" to build up to the point it's felt while
> braking (usually at highway speeds).
>
> Just as I ask all iKooks for a _single_ fact that backs up their entire
> belief system (and they almost never can answer that simple question), I
> ask anyone who claims their rotors warped what the measurements were.

Who remembers actual numbers from a couple of decades or more back? I
used to measure runout, thickness variation, taper, etc, compare to
specs, then machine. If they wouldn't clean up and still remain within
specs, they would be replaced, and that could be determined from the
measurements.

This was my preferred brake lathe;

https://www.ammcobrake.com/ammco-brake-lathe-model-4000b

Though not that current model.

You need to be very careful these days as some marques feature disc
rotors that cannot be machined. The rotor is considered a disposable
item just as much as the disc pads are. It's the only way by which the
manufacturers can get the friction coefficients up to acceptable levels.
>
> And they don't have them.
> Because...
> Because they simply guessed.
> Why?
>
> Intuition is a terrible thing.

--
Xeno

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

On 9/5/2022 1:46 am, Andy Burnelli wrote:
> Andy Burnelli wrote:
>
>> Intuition is a terrible thing.
>
> Don't even get me started on the "cellphones cause accidents" intuition, by
> the way, as monkeys intuit all sorts of stuff that doesn't show up in
> independent statistics outside {police,insurance,law} politics.
>
> If someone wants to claim "cellphones cause accidents", I only ask them for
> one fact, which they never can produce... and which is the only fact that
> matters.
>
> Marketing and politics takes advantage of people's emotions & intuition.

Distracted drivers using cellphones cause accidents.

--
Xeno

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

On 9/5/2022 3:33 am, Alan wrote:
> On 2022-05-08 8:46 a.m., Andy Burnelli wrote:
>> Andy Burnelli wrote:
>>
>>> Intuition is a terrible thing.
>>
>> Don't even get me started on the "cellphones cause accidents"
>> intuition, by
>> the way, as monkeys intuit all sorts of stuff that doesn't show up in
>> independent statistics outside {police,insurance,law} politics.
>>
>> If someone wants to claim "cellphones cause accidents", I only ask
>> them for
>> one fact, which they never can produce... and which is the only fact that
>> matters.
>>
>> Marketing and politics takes advantage of people's emotions & intuition.
>
> This isn't marketing.
>
> It's quite obvious logic.
>
> Reading text messages is not something you want people to be doing while
> driving.
>
> Writing them on a tiny smartphone onscreen keyboard is insane.
>
> Handsfree phone use with your smart assistant reading messages...
>
> ...sure, that's safe enough.

It is still a *distraction* from the primary function the driver should
be focussed on - driving.

--
Xeno

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

On 2022-05-08 5:09 p.m., Xeno wrote:
> On 9/5/2022 1:43 am, Andy Burnelli wrote:
>> NY wrote:
>>
>>> I was quite surprised that discs would get *that* hot, and that brake
>>> pads would withstand contact with red-hot metal.
>>
>> Regarding brake rotor warp (as in "potato chip"), that (almost) never
>> happens on rotors that didn't come out of the factory already warped.
>
> When I was doing a lot of brake repairs, and operating a brake lathe, I
> came across many warped rotors. One is required, after all, to check
> discs and drums for wear, distortion, runout and the like. In my
> experience, there were two possible factors involved in warped discs -
> overheating of rotors and incorrect sequence tightening of wheel nuts.
> Or simply overtightening. And, no, they didn't come out of the factory
> already warped. The worst for warping through overtightening were the
> integral hub and disc rotor. The separate rotor tended to be more prone
> to warping through overheating. Note too, a warped disc will evince
> different symptoms to a disc suffering pad deposition. The first car I
> owned that suffered from disc warping was a MkII 240 Ford Cortina but I
> drove that thing like a rally car back in the days.
>>
>> Regarding temperatures, the _melting_ point is (almost) impossible to
>> reach
>> in braking operations given the type of vehicles we're all talking about.
>
> I managed to reach it on one car I owned back in the early days of disc
> brakes. Admittedly, the rotor was sub par on the thickness hence a
> reduced heat capacity. It sure melted at the periphery though and was
> showing signs of heat stress all over - it was black and blue.  ;-)
>>
>> Regarding pad deposition, it's hard to believe, (even for me), but it
>> takes
>> only a small amount (almost impossible to measure directly) of "bump" of
>> collected pad chemical "footprint" to build up to the point it's felt
>> while
>> braking (usually at highway speeds).
>>
>> Just as I ask all iKooks for a _single_ fact that backs up their entire
>> belief system (and they almost never can answer that simple question), I
>> ask anyone who claims their rotors warped what the measurements were.
>
> Who remembers actual numbers from a couple of decades or more back? I
> used to measure runout, thickness variation, taper, etc, compare to
> specs, then machine. If they wouldn't clean up and still remain within
> specs, they would be replaced, and that could be determined from the
> measurements.
>
> This was my preferred brake lathe;
>
> https://www.ammcobrake.com/ammco-brake-lathe-model-4000b
>
> Though not that current model.
>
> You need to be very careful these days as some marques feature disc
> rotors that cannot be machined. The rotor is considered a disposable
> item just as much as the disc pads are. It's the only way by which the
> manufacturers can get the friction coefficients up to acceptable levels.

Yup!

My BMW 135i MSport's rotors are like that.

:-)

On 2022-05-08 5:10 p.m., Xeno wrote:
> On 9/5/2022 1:46 am, Andy Burnelli wrote:
>> Andy Burnelli wrote:
>>
>>> Intuition is a terrible thing.
>>
>> Don't even get me started on the "cellphones cause accidents"
>> intuition, by
>> the way, as monkeys intuit all sorts of stuff that doesn't show up in
>> independent statistics outside {police,insurance,law} politics.
>>
>> If someone wants to claim "cellphones cause accidents", I only ask
>> them for
>> one fact, which they never can produce... and which is the only fact that
>> matters.
>>
>> Marketing and politics takes advantage of people's emotions & intuition.
>
> Distracted drivers using cellphones cause accidents.
>

Of course they do.

Arlen is (as usual) utterly ignorant of reality.

On 2022-05-08 5:12 p.m., Xeno wrote:
> On 9/5/2022 3:33 am, Alan wrote:
>> On 2022-05-08 8:46 a.m., Andy Burnelli wrote:
>>> Andy Burnelli wrote:
>>>
>>>> Intuition is a terrible thing.
>>>
>>> Don't even get me started on the "cellphones cause accidents"
>>> intuition, by
>>> the way, as monkeys intuit all sorts of stuff that doesn't show up in
>>> independent statistics outside {police,insurance,law} politics.
>>>
>>> If someone wants to claim "cellphones cause accidents", I only ask
>>> them for
>>> one fact, which they never can produce... and which is the only fact
>>> that
>>> matters.
>>>
>>> Marketing and politics takes advantage of people's emotions & intuition.
>>
>> This isn't marketing.
>>
>> It's quite obvious logic.
>>
>> Reading text messages is not something you want people to be doing
>> while driving.
>>
>> Writing them on a tiny smartphone onscreen keyboard is insane.
>>
>> Handsfree phone use with your smart assistant reading messages...
>>
>> ...sure, that's safe enough.
>
> It is still a *distraction* from the primary function the driver should
> be focussed on - driving.
>

Sure...

....but if you want to go down that road, so is using or even listening
to the radio...

....to say nothing of talking to a passenger.

Sorry, but there are such things in this world as "reasonable limits"

On Mon, 09 May 2022 10:12:01 +1000, Xeno <xenolith@optusnet.com.au> wrote:

> On 9/5/2022 3:33 am, Alan wrote:
>> On 2022-05-08 8:46 a.m., Andy Burnelli wrote:
>>> Andy Burnelli wrote:
>>>
>>>> Intuition is a terrible thing.
>>>
>>> Don't even get me started on the "cellphones cause accidents"
>>> intuition, by
>>> the way, as monkeys intuit all sorts of stuff that doesn't show up in
>>> independent statistics outside {police,insurance,law} politics.
>>>
>>> If someone wants to claim "cellphones cause accidents", I only ask
>>> them for
>>> one fact, which they never can produce... and which is the only fact
>>> that
>>> matters.
>>>
>>> Marketing and politics takes advantage of people's emotions &
>>> intuition.
>> This isn't marketing.
>> It's quite obvious logic.
>> Reading text messages is not something you want people to be doing
>> while driving.
>> Writing them on a tiny smartphone onscreen keyboard is insane.
>> Handsfree phone use with your smart assistant reading messages...
>> ...sure, that's safe enough.
>
> It is still a *distraction* from the primary function the driver should
> be focussed on - driving.
>

So is talking to the pax and listening to the radio.

On 5/8/2022 5:10 PM, Xeno wrote:
> On 9/5/2022 1:46 am, Andy Burnelli wrote:
>> Andy Burnelli wrote:
>>
>>> Intuition is a terrible thing.
>>
>> Don't even get me started on the "cellphones cause accidents"
>> intuition, by
>> the way, as monkeys intuit all sorts of stuff that doesn't show up in
>> independent statistics outside {police,insurance,law} politics.
>>
>> If someone wants to claim "cellphones cause accidents", I only ask
>> them for
>> one fact, which they never can produce... and which is the only fact that
>> matters.
>>
>> Marketing and politics takes advantage of people's emotions & intuition.
>
> Distracted drivers using cellphones cause accidents.

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

According to the the NHTSA, for 2019 in the U.S.:

Total fatal crashes: 33,244
Total fatalities in fatal crashes: 36,096
Fatal crashes caused by distracted driving: 2,895 (9%)
Total fatalities in fatal crashes caused by distracted driving: 3,142 (9%)
Number of cellphone distraction-affected fatal crashes: 387 (13%)
Number of cellphone distraction-affected fatalities: 422 (13%)

So about 87% of distracted driving crashed and fatalities were caused by
factors other than cell phones.

So about 1.2% of fatal crashes (9% x 13%) were caused by drivers
distracted by cell phones.

The NHTSA mentions other distractions that make up the 87%, "eating and
drinking, talking to people in your vehicle, fiddling with the stereo,
entertainment or navigation system."

<https://www.iii.org/fact-statistic/facts-statistics-distracted-driving>

Using a phone while driving is a distraction even when it's being used
hands-free.

Not sure how to address the other 87% of distracted driving fatalities,
or even the portion of the 13% caused by cell phone use since even
hands-free doesn't solve the distracted driving problem. Texting while
driving could be addressed via technology but it would have to
distinguish between drivers and passengers. In the two vehicles we have
owned with built in navigation systems, you can't enter addresses when
the vehicle is moving, which is a real pain when a passenger could be
the one using the system. There were workarounds but they were beyond
the capability of most owners.

Xeno wrote:

> It is still a *distraction* from the primary function the driver should
> be focussed on - driving.

Hi Xeno,

The problem here is that intuition is a terrible thing when it's wrong.

I don't discuss anything with Rod Speed or Alan Baker (or Jock, who is just
Rod Speed by another nym, et. al), but you can comprehend basic logic.

First off, _everyone_ (including me!) would "think" that cellphones are a
_sufficient_ distraction to cause accidents, and, in fact, they do.

Except....

There is zero evidence of that happening, en masse, in the "good" data,
which is the US Census Bureau data from the 1920's to current on traffic
accidents in each state (individually & combined) over the years.

None. zip. nada.

The _only_ place you see this supposed increase in accidents is in the
bullshit data {e.g., news anecdotes, lawyer web pages, insurance company
web pages and police/politician web pages}.

Now maybe lawyers and especially insurance companies know more than does
the US Census Bureau of traffic accidents, but that's not likely. It's far
more likely their data is skewed. So let's ignore their skewed crap at
first (we can always come back to their crap when/if we need to if we want
to).

If we look at the best data there is for US traffic accidents, you find
zero effect from the very clear ownership information of cellphones in the
US which sky rocketed in a decade and yet accident rates didn't change a
blip from their general downward trend that they always had (last I checked
was pre-covid days but _rates_ don't depend on miles driven so I'd expect
no change from covid given cellphone ownership didn't change either).

No adult discussion is possible until you agree on that fact (which I don't
expect anyone to agree with until they check for themselves). Once they do
agree on that fact, then (and only then) we can progress to why.

I think I know _why_ cellphones have zero effect on the overall accident
rate and the reason why I think is that people who will have accidents will
_always_ have accidents (essentially because they're stupid people when it
comes to driving - but let's not go there yet). (There's a reason insurance
companies give discounts to intelligent people.)

The fact is that cellphones _are_ a distraction, and the fact is there are
plenty of bigger and smaller distractions when driving.

I don't expect anyone to understand a word I'm saying above, mainly because
people are stuck on the idea that cellphones _do_ cause accidents enough to
change the rate, but the facts show that just isn't true.

Intuition is a terrible thing when it's wrong.

Anyway, I think the reason the fact is that cellphones didn't change the
accident rate had nothing to do with laws (as people don't follow the law
and even if they did, laws were enacted at different times in different
states and the rates didn't show any change anyway)...

Nope.

The reason, I think cellphones didn't change the rates is that, instead of,
oh, say, the top ten, twenty, or fifty or even a hundred distractions that
"can" happen while driving, cellphones phones simply took the place of one
of them, oh, say, just making this up, say it's number eight.

So what happened is the previous number 8 distraction (say that was crying
babies) just moved to number 9, and the total number of distractions (say
it was 100 before, changed to 101), and that's why there's no change in
accident rates.

In summary, three points I make for intelligent people to discuss.
1. Intuition says they are a distraction and intuition then tells us that
this added distraction should increase accident rates...
2. But fact tells us this isn't happening (and never did).
3. Therefore, if we agree with point 1 and point 2, then it behooves us to
_understand_ why.
--
I don't expect anyone on this newsgroup to own the intelligence to
comprehend what I just said, even fewer than zero to agree with what I just
said - and that's OK. It just means I'm preaching to a blank stare.

Andy Burnelli wrote:

> Intuition is a terrible thing when it's wrong.

BTW, it's the _same_ wrong intuition on the warped rotors, or the intuition
that if you pay more for an iPhone it _must_ be more powerful, etc.

Intuition is a terrible thing.

In the case of cellphone accidents, intuition is a terrible thing, since
the good data on accident rates shows _zero_ effect of cellphone ownership.
--
And those morons hoping to poke holes in my argument need to read my words
as rates are what I'm talking about, and not injuries (which are a
second-order effect), and I'm not talking use because there is no reliable
data on use so all we have that's reliable data is ownership percentages.

Xeno wrote:

>> Marketing and politics takes advantage of people's emotions & intuition.
>
> Distracted drivers using cellphones cause accidents.

Be careful when comprehending what I said, and not what you _think_ I said.

Rain causes accidents.
A good economy causes accidents.
Construction causes accidents.
Hot coffee causes accidents.
Crying babies cause accidents.
Driving while upset causes accidents.
Scratching your ass while driving causes accidents.
.... (list goes on forever)...

The question to ask is where in that list of infinite things that cause
accidents, is where you'd put cellphones, and, then... why didn't doing
that have _any_ effect whatsoever on the accident rate?

What you want if you are a politician or a lawyer or an insurance company
is to talk "accidents" (the more sensational the better).

But what you do if you are a scientist is talk accident rates.

If you want to talk accidents, then I can prove anything you want me to
prove simply because I can find a bacon cheeseburger which caused an
accident.

What you have to show is the _accident rate_ did "something" before,
during, and after the meteoric rise in cellphone ownership percentages.

And you can't.
Not without picking _only_ lawyer web sites, or insurance web sites, or
political bullshit web sites (particularly from police agencies wanting
more money), etc.

But try to find a _single_ USA accident rate set of reliable data that
covers the time period from _before_, during, and _after_ cellphone
ownership has skyrocketed that shows _any_ effect whatsoever of cellphone
ownership on accident rates.

Without that data, you're just guessing.
I don't know if I mentioned it yet but intuition is a terrible thing.
--
Note I don't talke use rates - not because it's not important - as it is -
but the problem is that useage is an unknown. We only have good data on
ownership percentages. Not on usage rates while driving.

Andy Burnelli wrote:

>>> Marketing and politics takes advantage of people's emotions & intuition.
>>
>> Distracted drivers using cellphones cause accidents.
>
> Be careful when comprehending what I said, and not what you _think_ I said.

Bear in mind I made a mistake in what I said since it was off the cuff...

I looked back and I said "accidents" so please accept my apologies in that
I meant the accident rate, as _anything_ causes accidents (even a duck
waddling across the road or fiddling with the radio tuner, etc.).

I type Usenet messages off the cuff, so what I'm saying is nobody has ever
found in the _reliable_ data (not cherry picked lawyer web sites!) any
effect whatsoever on the accident rate before, during, and after cell phone
ownership percentages skyrocketed.

Nobody can discuss why until they agree with that fact.
If you disagree with that fact, all you have to do is provide the data.

But the only data you can find that meets your intuition is that from
insurance companies, legal companies, and government agencies that make
money of ticketing.

Surely if the accident rates did have an effect from cellphone ownership
going from zero to nearly 100% in the USA, then you should see something in
the accident rates, Right?

Notice may argument is very clear.
The accident rate in all the reliable data shows no effect whatsoever.

The question is why.
--
Note I'm well aware every moron on the planet _believes_ that cellphones
must have an effect on the accident rate - but I will ask them to prove it
without having to resort to the three types of skewed sites listed above.

sms wrote:

> According to the the NHTSA, for 2019 in the U.S.:
>
> Total fatal crashes: 33,244
> Total fatalities in fatal crashes: 36,096
> Fatal crashes caused by distracted driving: 2,895 (9%)
> Total fatalities in fatal crashes caused by distracted driving: 3,142 (9%)
> Number of cellphone distraction-affected fatal crashes: 387 (13%)
> Number of cellphone distraction-affected fatalities: 422 (13%)
>
> So about 87% of distracted driving crashed and fatalities were caused by
> factors other than cell phones.
>
> So about 1.2% of fatal crashes (9% x 13%) were caused by drivers
> distracted by cell phones.
>
> The NHTSA mentions other distractions that make up the 87%, "eating and
> drinking, talking to people in your vehicle, fiddling with the stereo,
> entertainment or navigation system."
>
> <https://www.iii.org/fact-statistic/facts-statistics-distracted-driving>
>
> Using a phone while driving is a distraction even when it's being used
> hands-free.
>
> Not sure how to address the other 87% of distracted driving fatalities,
> or even the portion of the 13% caused by cell phone use since even
> hands-free doesn't solve the distracted driving problem. Texting while
> driving could be addressed via technology but it would have to
> distinguish between drivers and passengers. In the two vehicles we have
> owned with built in navigation systems, you can't enter addresses when
> the vehicle is moving, which is a real pain when a passenger could be
> the one using the system. There were workarounds but they were beyond
> the capability of most owners.

Steve is a politician, so I simply call him out on his cherry picked
bullshit above where I doubt Steve is smart enough to realize he used every
bullshitter's trick in the book to make his bullshit argument above.

Remember my main point which is intuition is a terrible thing indeed.
What matters are only the facts.

1. Nobody knows what distraction caused most accidents, as all those
"distracted driving" statistics are bullshit (ask Steve _how_ they gather
that data). HINT: I know how. Does Steve?

2. Almost _all_ accidents are caused by distracted driving, so 9% is
_clearly_ cherry-picked bullshit. It's likely almost 100% (barring
mechanical failures, for example or trees falling off of overpasses or
someone shooting someone etc.).

3. What matters is the accident rate in the USA before, during & after the
meteoric rise of cellphone ownership. HINT: I know that too. Does Steve?

4. Injuries are a second order effect so far removed from accidents that
_anyone_ how resorts to 'fatalities' is _always_ a bullshitter for a huge
number of reasons, not the least of which is that you can't have any
injuries if the accidents don't happen and more to the point that
fatalities are related to a huge number of factors, some of which
cellphones actually reduce (since they speed up ambulance service, for
example - as does traffic routing).

Be careful about anyone bringing fatalities into the discussion since
that's a clear mark of a bullshitter if we're talking about accident rates
given you can't have fatalities if you don't have the accident first.
--
What actually matters is the cellphone _use_ while driving, but NOBODY has
that statistic (and yes, I know how the NHTSA collects that data annually).

Xeno wrote:

>> Regarding brake rotor warp (as in "potato chip"), that (almost) never
>> happens on rotors that didn't come out of the factory already warped.
>
> When I was doing a lot of brake repairs, and operating a brake lathe, I
> came across many warped rotors.

Remember, warp (as in potato chip) is _different_ from runout.
Warp will cause runout but so will a lot of other things cause runout.

> One is required, after all, to check
> discs and drums for wear, distortion, runout and the like.

Let's take those items one by one:
a. wear
b. distortion
c. runout
d. And the like

Which one of those are you considering "warp" because if you say "all of
them" then you're saying everything _is_ warp, and I'm not saying that.

I'm saying warp is something very specific, and it's _not_ runout (which is
something else altogether), and neither is it wear.

I don't know what you mean by "distortion" but that's the closest term you
used to what is warp (as in potato chip).

Warp is checked against known a flat surface, as you're well aware, where
warp, the way I'm using it, means one side (at least) of the rotor is not
laying flat on the test bench (the other side may or may not be parallel as
that's even worse if it's not equivalent).

We should assume solid rotors for simplicity, but I understand that common
vehicular rotors often have two discs separated by fins so there are a few
measurements we can make against a flat bench surface to measure warp.

> In my
> experience, there were two possible factors involved in warped discs -
> overheating of rotors and incorrect sequence tightening of wheel nuts.

Warp (as in potato chip) will certainly cause runout but runout itself
isn't warp.

> Or simply overtightening.

Runout isn't warp.

> And, no, they didn't come out of the factory
> already warped.

I only bring that up because morons always try to find holes in my
scientifically based arguments and that's one of the holes they are
desperate to find.

> The worst for warping through overtightening were the
> integral hub and disc rotor.

Runout isn't warp.

And besides, the simplest cure for what people "call" warp often is a
rebedding procedure which has _zero_ effect on the bolt torque and zero
effect on runout.

> The separate rotor tended to be more prone
> to warping through overheating.

Warp almost never happens and anyone who says it did never mesaured it.
Not even you Xeno.
Nobody does (except people who _understand_ what warp is, as in potato
chip).

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).

> Note too, a warped disc will evince
> different symptoms to a disc suffering pad deposition. \\

Holy Shit. Of course. A truly warped rotor (as in potato chip) is fucked up
beyond belief. No amount of pad rebedding will solve a warped rotor (as in
potato chip).

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
there if the warp (as in potato chip) is appreciable.

> The first car I
> owned that suffered from disc warping was a MkII 240 Ford Cortina but I
> drove that thing like a rally car back in the days.

I'm going to have to call bullshit on the warp (as in potato chip) since
there is zero chance that you measured it (using the proper tools for warp,
which, as you well know, requires a known straight tool).

>>
>> Regarding temperatures, the _melting_ point is (almost) impossible to reach
>> in braking operations given the type of vehicles we're all talking about.
>
> I managed to reach it on one car I owned back in the early days of disc
> brakes. Admittedly, the rotor was sub par on the thickness hence a
> reduced heat capacity. It sure melted at the periphery though and was
> showing signs of heat stress all over - it was black and blue. ;-)

I doubt it. Rotors are made of a variety of steels (e.g., motorcycle rotors
are often stainless steel) but even for the worst quality cast iron rotors,
look up the temperature it takes to melt them.

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).

Look it up.

> Who remembers actual numbers from a couple of decades or more back? I
> used to measure runout, thickness variation, taper, etc, compare to
> specs, then machine.

Yes. I know. But did you measure warp (as in potato chip)?

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).

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).

> 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?

> This was my preferred brake lathe;
> https://www.ammcobrake.com/ammco-brake-lathe-model-4000b
>
> Though not that current model.

If the rotor was truly warped (as in potato chip), I would think the only
feasible solution is to junk it. I'm sure some 'can' be machined to spec,
but I, for one, wouldn't want that rotor on my passenger vehicle.

> You need to be very careful these days as some marques feature disc
> rotors that cannot be machined. The rotor is considered a disposable
> item just as much as the disc pads are. It's the only way by which the
> manufacturers can get the friction coefficients up to acceptable levels.

Did you machine stainless steel rotors?
--
Bear in mind I speak facts first, and then I make assessments based on
those facts. You can't argue with assessments until you agree on the facts
first (or disagree - and then we work on the facts).

On 9/5/2022 7:15 pm, Andy Burnelli wrote:
> Xeno wrote:
>
>>> Regarding brake rotor warp (as in "potato chip"), that (almost) never
>>> happens on rotors that didn't come out of the factory already warped.
>>
>> When I was doing a lot of brake repairs, and operating a brake lathe,
>> I came across many warped rotors.
>
> Remember, warp (as in potato chip) is _different_ from runout.
> Warp will cause runout but so will a lot of other things cause runout.
>
>> One is required, after all, to check discs and drums for wear,
>> distortion, runout and the like.
>
> Let's take those items one by one:
> a. wear
> b. distortion
> c. runout
> d. And the like
>
> Which one of those are you considering "warp" because if you say "all of
> them" then you're saying everything _is_ warp, and I'm not saying that.
>
> I'm saying warp is something very specific, and it's _not_ runout (which is
> something else altogether), and neither is it wear.
>
> I don't know what you mean by "distortion" but that's the closest term you
> used to what is warp (as in potato chip).
>
> Warp is checked against known a flat surface, as you're well aware, where
> warp, the way I'm using it, means one side (at least) of the rotor is not
> laying flat on the test bench (the other side may or may not be parallel as
> that's even worse if it's not equivalent).
>
> We should assume solid rotors for simplicity, but I understand that common
> vehicular rotors often have two discs separated by fins so there are a few
> measurements we can make against a flat bench surface to measure warp.
>
>> In my experience, there were two possible factors involved in warped
>> discs - overheating of rotors and incorrect sequence tightening of
>> wheel nuts.
>
> Warp (as in potato chip) will certainly cause runout but runout itself
> isn't warp.
>
>> Or simply overtightening.
>
> Runout isn't warp.
>
>> And, no, they didn't come out of the factory already warped.
>
> I only bring that up because morons always try to find holes in my
> scientifically based arguments and that's one of the holes they are
> desperate to find.
>
>> The worst for warping through overtightening were the integral hub and
>> disc rotor.
>
> Runout isn't warp.
>
> And besides, the simplest cure for what people "call" warp often is a
> rebedding procedure which has _zero_ effect on the bolt torque and zero
> effect on runout.
>
>> The separate rotor tended to be more prone to warping through
>> overheating.
>
> Warp almost never happens and anyone who says it did never mesaured it.
> Not even you Xeno.
> Nobody does (except people who _understand_ what warp is, as in potato
> chip).
>
> 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
>
>> Note too, a warped disc will evince different symptoms to a disc
>> suffering pad deposition. \\
>
> Holy Shit. Of course. A truly warped rotor (as in potato chip) is fucked up
> beyond belief. No amount of pad rebedding will solve a warped rotor (as in
> potato chip).

I wasn't saying anything about rebedding at all.
>
> 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.

> there if the warp (as in potato chip) is appreciable.
>> The first car I owned that suffered from disc warping was a MkII 240
>> Ford Cortina but I drove that thing like a rally car back in the days.
>
> I'm going to have to call bullshit on the warp (as in potato chip) since
> there is zero chance that you measured it (using the proper tools for warp,
> which, as you well know, requires a known straight tool).

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.
>
>>>
>>> Regarding temperatures, the _melting_ point is (almost) impossible to
>>> reach
>>> in braking operations given the type of vehicles we're all talking
>>> about.
>>
>> I managed to reach it on one car I owned back in the early days of
>> disc brakes. Admittedly, the rotor was sub par on the thickness hence
>> a reduced heat capacity. It sure melted at the periphery though and
>> was showing signs of heat stress all over - it was black and blue.  ;-)
>
> I doubt it. Rotors are made of a variety of steels (e.g., motorcycle rotors

I don't, I saw the evidence.

> 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 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.
>
> Look it up.

No need, I saw the evidence directly.
>
>> Who remembers actual numbers from a couple of decades or more back? I
>> used to measure runout, thickness variation, taper, etc, compare to
>> specs, then machine.
>
> Yes. I know. But did you measure warp (as in potato chip)?

Yes, I did, with a dial indicator. Definitely warp.
>
> 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.
>
> 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.
>
>> 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.
>
>> This was my preferred brake lathe;
>> https://www.ammcobrake.com/ammco-brake-lathe-model-4000b
>>
>> Though not that current model.
>
> If the rotor was truly warped (as in potato chip), I would think the only
> feasible solution is to junk it. I'm sure some 'can' be machined to spec,
> but I, for one, wouldn't want that rotor on my passenger vehicle.
>
>> You need to be very careful these days as some marques feature disc
>> rotors that cannot be machined. The rotor is considered a disposable
>> item just as much as the disc pads are. It's the only way by which the
>> manufacturers can get the friction coefficients up to acceptable levels.
>
> Did you machine stainless steel rotors?

Nope. never saw a stainless steel rotor when I was involved in brakes.
All seemed to have been cast iron of varying grades. That said, I didn't
work on exotic cars nor did I work on motorcycles or aircraft. YMMV.

--
Xeno

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

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.

What does that tell us about the intuition of human beings?

>> Did you machine stainless steel rotors?
>
> Nope. never saw a stainless steel rotor when I was involved in brakes.
> All seemed to have been cast iron of varying grades. That said, I didn't
> work on exotic cars nor did I work on motorcycles or aircraft. YMMV.

On 10/5/2022 1:39 am, 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.

Dial indicator with the disc mounted on a brake lathe is my choice. Much
more accurate and allows you to ascertain exactly where the runout is
and enables the mechanic to differentiate between such things at
thickness variation, taper, hard spots and warp. A long flat edge and
feeler gauges isn't going to get you there. What you also need, in
particular for assessing thickness variation and taper, is a disc
micrometer;

https://www.starrett.com/metrology/product-detail/458BXR

With this micrometer the mechanic can check thickness variation and
taper in the disc running surface as well as groove depth, an asset no
brake mechanic should be without. You can also get disc rotor vernier
calipers which, though not as accurate, will allow the mechanic to get
the job done with a minimum of fuss.

https://m.media-amazon.com/images/I/61ObCDKm14S._AC_SX679_.jpg

A long flat edge and feelers just doesn't cut it if you are looking for
accuracy. You're just not getting meaningful measurements.

> 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"

Well, as I said, I have seen it, felt the symptoms and measured the 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.

Deposition creates a *different* symptom to that caused by warp when
driving. Any good mechanic should be able to differentiate.
>
> 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

Of all those materials, the only one in *common use* is cast iron. The
downside in cars is the increase in unsprung weight. Steel is for racing
cars and they are very prone to warping. Laminated steel is less prone
to warping but this material/type isn't common in production passenger
vehicles. More an aftermarket thing for the racing fraternity. Yje high
carbon iron and ceramics are only to be found on the upper end cars.
>
>> 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."

What is *normal driving*? I used to hammer the brakes on my cars but I
no longer do that - I'm aging gracefully. There is no longer an
imperative to save 5 or 10 seconds on a short journey - I've all the
time in the world these days and I no longer live in a capital city.
I've done the tree/sea change and now live in a small rural/seaside city
of 75,000 people. Drive 1 kilometre from my home and I'm out in the boonies.
>
> 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?

When assessing serviceability of brake components I *never* rely on or
use intuition. I always measure.
>
>>> 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

Warp will *create* runout. It has to.

> 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. :)

The manufacturers specify a *minimum thickness* for rotors. It's but a
simple calculation from *measurements* to work out whether a rotor will
clean up and still be within spec. The is no need to measure, machine,
*remeasure* then discard.

> "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."

With sliding/floating calipers, it is quite common for rotors to get
hotter on one side. It's the nature of the beast. That is why,
particularly on sliders, that one pad wears out before 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).

Not everyone drives their daily driver like a grandpa. I certainly
didn't back in the day.
>
> "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."

It depends......
>
>>> 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).

On 5/9/2022 5:17 PM, Xeno wrote:
> On 10/5/2022 1:39 am, 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.
>
> Dial indicator with the disc mounted on a brake lathe is my choice. Much
> more accurate and allows you to ascertain exactly where the runout is
> and enables the mechanic to differentiate between such things at
> thickness variation, taper, hard spots and warp. A long flat edge and
> feeler gauges isn't going to get you there. What you also need, in
> particular for assessing thickness variation and taper, is a disc
> micrometer;

In the early days of disc brakes, the rotors were heavy and thick and
could be resurfaced multiple times. Brake jobs were pretty inexpensive
since rotors didn't need to be replaced, they were dropped onto a lathe.
Back when I did my own brake jobs I would take the rotors to my
brother-in-law's shop and he would resurface them for me, but you could
also get a machine shop to resurface them for $10 each.

But the mass of thick rotors negatively affected fuel economy so much
thinner rotors began to be used, and they usually can't be resurfaced
even once, they have to be replaced at the same time the brake pads are
replaced. They also warp much easier. It also actually became not that
uncommon to replace warped rotors, but not the pads, since the pads were
fine.

sms wrote:

> But the mass of thick rotors negatively affected fuel economy so much
> thinner rotors began to be used, and they usually can't be resurfaced
> even once, they have to be replaced at the same time the brake pads are
> replaced.

Bullshit.

The time to replace rotors is when they no longer meet the specs, and there
are a few specs that they need to meet (cracks, thickness, gouges, etc.),
but the main spec is the thickness.

I've seen many people say the bullshit you say but the fact is you measure
them, like Xeno and I do, and if they're within specs, you keep them.

It doesn't matter how many brake pads you replaced.

> They also warp much easier. It also actually became not that
> uncommon to replace warped rotors, but not the pads, since the pads were
> fine.

More bullshit.

Read this before you bullshit us please.
<https://ricksfreeautorepairadvice.com/warped-brake-rotors/>

It's impossible for rotors to warp (as in potato chip), and everyone who
says they do, has _never_ measured it, least of all you, Steve.
--
The problem with people like Steve is they don't know how stupid they are.

Xeno wrote:

>> Agreed. All you need is a long flat edge and feeler gauges as a minimum.
>
> Dial indicator with the disc mounted on a brake lathe is my choice.

Hi Xeno,
I respect your knowledge and experience so I won't harp on it with you.
I deal all the time with iKooks who can't handle the facts.

Respect me that I'm highly educated, intelligent, and I speak the facts.
Hence, I simply point to cold hard non-intuitive facts & leave it at that.

<https://ricksfreeautorepairadvice.com/warped-brake-rotors/>
"Calling it brake rotor warp demonstrates a complete misunderstanding
of the metallurgy and the braking process"

<https://trade.mechanic.com.au/news/solved-the-mystery-of-warped-brake-rotors>
"Contrary to popular belief, brake rotors... don't warp, no matter
how aggressively a vehicle is driven."

<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."

<https://www.buybrakes.com/help/why-do-brake-rotors-warp/>
"The thing is, rotors don�t actually permanently warp."
--
Intuition is a terrible thing because it fears facts.

On Mon, 9 May 2022 16:39:09 +0100, Andy Burnelli <spam@nospam.com> wrote:

>My point is that nobody who says warp (as in potato chip) measures that
>warp (as in potato chip),
>
>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.
>
>>> 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
>
>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).
>
>However, you have to respect my knowledge that _reliable_ sources say
>otherwise and that runout isn't warp (as in potato chip)
>
>I even doubt machining could fix any appreciable warp (as in potato chip),
>
>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).
>
>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.
>
>>> Yes. I know. But did you measure warp (as in potato chip)?

>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.
>
>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.
>
>>> 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?
>>
>
>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.
>I respect you. If you can find a _single_ reference on this planet that is
>reliable that can show brake rotors in passenger vehicles truly warping (as
>in potato chip), I promise you I will _read_ that reference you find.
>
>Just as cellphones don't change the accident rate is a completely
>unintuitive fact, brake rotors don't warp (as in potato chip) in passenger
>vehicles.

I agree that rotors don't warp "as in a potato chip."
Rotors do warp "as in a warped rotor."

On 11/5/2022 11:41 am, Vic Smith wrote:
> On Mon, 9 May 2022 16:39:09 +0100, Andy Burnelli <spam@nospam.com> wrote:
>
>
>> My point is that nobody who says warp (as in potato chip) measures that
>> warp (as in potato chip),
>>
>> 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.
>>
>>>> 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
>>
>> 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).
>>
>> However, you have to respect my knowledge that _reliable_ sources say
>> otherwise and that runout isn't warp (as in potato chip)
>>
>> I even doubt machining could fix any appreciable warp (as in potato chip),
>>
>> 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).
>>
>> 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.
>>
>>>> Yes. I know. But did you measure warp (as in potato chip)?
>
>> 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.
>>
>> 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.
>>
>>>> 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?
>>>
>>
>> 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.
>> I respect you. If you can find a _single_ reference on this planet that is
>> reliable that can show brake rotors in passenger vehicles truly warping (as
>> in potato chip), I promise you I will _read_ that reference you find.
>>
>> Just as cellphones don't change the accident rate is a completely
>> unintuitive fact, brake rotors don't warp (as in potato chip) in passenger
>> vehicles.
>
> I agree that rotors don't warp "as in a potato chip."
> Rotors do warp "as in a warped rotor."

Yeah, "as in a potato chip" would be a bit too extreme. OTOH, I have
*measured* warped rotors that were warped sufficiently to have an effect
on the *steering*, even some that were too far gone to machine whilst
still retaining minimum thickness. Note, not seen warping on ventilated
discs that I can recall, just the old solid discs. The ventilated discs
seem rather more robust.

--
Xeno

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

Xeno wrote:

> Yeah, "as in a potato chip" would be a bit too extreme. OTOH, I have
> *measured* warped rotors that were warped sufficiently to have an effect
> on the *steering*, even some that were too far gone to machine whilst
> still retaining minimum thickness. Note, not seen warping on ventilated
> discs that I can recall, just the old solid discs. The ventilated discs
> seem rather more robust.

Again, I'm going to repeat I'm highly educated, intelligent, and I've
researched this subject for years, so just saying "I measured it" is like
saying "I measured the earth and it's still flat, dammit".

Having taken on the iKooks with facts, rest assured I believe a lot of
people strongly believe a lot of things that just aren't the case.

If a vehicle shudders while braking, people intuit that their rotors
warped, and, I don't blame them for thinking that any more than I blame
people for thinking the earth is flat, since it makes sense in terms of the
intuition of a smart monkey - which is the intuition we _all_ have.

Including me.

The only difference with me is I don't trust my intuition.
Most people trust their intuition well neigh more than they do the facts.

Whenever that happens, I simply ask those people to provide facts backing
up their claims, and, rest assured, they never do (because they can't).

Rest assured in most of those cases I _do_ supply the facts, as I did here.
Almost all the time they don't even read the cited references.
Worse, they deny every fact in them _without_ even reading them.

There's no way to carry on an adult conversation with people like that.
As I said from the start, intuition is a terrible thing indeed.

You learn that when you learn quantum physics, for example.
There, intuition is _always_ wrong.

The reason is that we own the intuition of monkeys... all of us.
Including me.

That's why I don't trust my intuition.
I trust in facts.

My intuition says that rotors should get hot and start "warping"; but the
facts say otherwise, just as my intuition says that cellphones must be
causing increased accident rates; but the facts say otherwise.

What I find most interesting is people blame me for their intuition being
wrong, where they should blame evolution for giving humans the intuition of
a monkey.

BTW, with respect to the iKooks, what MARKETING does is play on intuition.
Same with automotive fluids, brake pads, tires, and, yes, rotors.

Intuition is a terrible thing for a whole bunch of reasons, the most
important of which it is almost always wrong - but the next most important
reason is that marketing preys on people's intuition.

If marketing gold plates the letters on the marquee, people "think" it's
better, or, more to the point, if a car simply has DTV caused by pad
deposition, the shop tells them they need new rotors and pads (and maybe
even new calipers and a few other things too).

On the pads, if MARKETING throws in a spec of dust and calls it "ceramic"
people think it too is better (they don't even know what the cold/hot
friction ratings are as that is an unimportant detail to them - all that
matters is that MARKETING called it "ceramic"), and if they put the word
"performance" on a tire, people think it's better too.

The list of false beliefs people own based on a hijack of their intuition
by MARKETING probably will never end, at least until humans evolve further
away from having the intuition necessary to grab a branch that is far away
and intuit that it will hold up their bodies under the force of gravity.

BTW, gravity is _another_ thing people intuit, where it doesn't even exist.
But that's a topic for folks who have a background in space & time were
we're moving in an orthogonal dimension to space at nearly the speed of
light (which is felt by we monkeys as what we call the "force" of gravity).

Anyway, I provided my references, and folks are welcome to read them.
<https://ricksfreeautorepairadvice.com/warped-brake-rotors/>
"Calling it brake rotor warp demonstrates a complete misunderstanding
of the metallurgy and the braking process"

<https://trade.mechanic.com.au/news/solved-the-mystery-of-warped-brake-rotors>
"Contrary to popular belief, brake rotors... don't warp, no matter
how aggressively a vehicle is driven."

<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."

<https://www.buybrakes.com/help/why-do-brake-rotors-warp/>
"The thing is, rotors don't actually permanently warp."

If someone has a reliable reference that speaks of "warp" as if it really
can happen, I'll read it, but rest assured, no reliable references will be
found because it's impossible for rotors to do what people intuit they do.

Doesn't matter if the rotor is solid or not, if they're sold in the USA,
they meet a spec that makes it impossible - as the fluid would boil well
before the rotor could get hot enough, and the rest of the brake system
components would disintegrate well before the rotor ever got hot enough.

In summary, on the topic of rotor "warp", I'll read any reliable reference
that people bring up to back up their intuition, but otherwise, there's no
sense in this as it's like trying to explain to people that the earth isn't
in the center of the solar system if they intuit otherwise and if they
believe their own intuition far more than they believe in actual facts.

Intuition is a terrible thing indeed.
--
I agree with any logical & rational point of view, no matter from whom.

"Vic Smith" <thismailautodeleted@comcast.net> wrote in message
news:2b4m7hp2le1tl7anjbnleua0jiu1qsmfep@4ax.com...
> I agree that rotors don't warp "as in a potato chip."
> Rotors do warp "as in a warped rotor."

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 whole area?
I'd always thought that a warped disc had a wavy surface like a potato chip
(aka potato crisp in the UK) or a vinyl LP - ie where the pads had to move
parallel to the rotor axis to remain in contact with the disc that was not a
perfectly flat plane.

Presumably if the surface becomes glazed in some parts and/or roughened in
some parts that causes different amounts of wear in the different areas,
exacerbating the problem.

What is the advice for avoiding rotor warping? How should one brake
differently to avoid it? I presume using engine braking (selecting a lower
gear) when going down a long hill reduces the amount and/or time that the
pads have to be in contact with the discs. I've also heard it said that if
you hold the car on the footbrake (rather than applying the handbrake or
transmission lock) after braking to a halt, the area of the disc that's in
contact with the hot disc will not be able to cool as much as the rest of
the disc, leading to "rotor warping" - which is another reason (in addition
to dazzling the person behind with your brake lights) for applying the
handbrake whenever you come to a stop. As my driving instructor drummed in
to me: "footbrake to stop the car; handbrake to *stay* stopped" - I can
still "hear" him saying that 40 years later ;-)

On 11/5/2022 7:54 pm, Andy Burnelli wrote:
> Xeno wrote:
>
>> Yeah, "as in a potato chip" would be a bit too extreme. OTOH, I have
>> *measured* warped rotors that were warped sufficiently to have an
>> effect on the *steering*, even some that were too far gone to machine
>> whilst still retaining minimum thickness. Note, not seen warping on
>> ventilated discs that I can recall, just the old solid discs. The
>> ventilated discs seem rather more robust.
>
> Again, I'm going to repeat I'm highly educated, intelligent, and I've
> researched this subject for years, so just saying "I measured it" is like
> saying "I measured the earth and it's still flat, dammit".
>
> Having taken on the iKooks with facts, rest assured I believe a lot of
> people strongly believe a lot of things that just aren't the case.
>
> If a vehicle shudders while braking, people intuit that their rotors
> warped, and, I don't blame them for thinking that any more than I blame

I, for one, know that warped rotors do not necessarily *shudder*. What's
more, I can differentiate between *shudder* and the myriad other
symptoms that manifest themselves from brake faults.

> people for thinking the earth is flat, since it makes sense in terms of the
> intuition of a smart monkey - which is the intuition we _all_ have.
>
> Including me.
>
> The only difference with me is I don't trust my intuition.
> Most people trust their intuition well neigh more than they do the facts.

Intuition, for the most part, *develops* from experience.
>
> Whenever that happens, I simply ask those people to provide facts backing
> up their claims, and, rest assured, they never do (because they can't).
>
> Rest assured in most of those cases I _do_ supply the facts, as I did here.
> Almost all the time they don't even read the cited references.
> Worse, they deny every fact in them _without_ even reading them.
>
> There's no way to carry on an adult conversation with people like that.
> As I said from the start, intuition is a terrible thing indeed.
>
> You learn that when you learn quantum physics, for example. There,
> intuition is _always_ wrong.
> The reason is that we own the intuition of monkeys... all of us.
> Including me.
>
> That's why I don't trust my intuition. I trust in facts.
>
> My intuition says that rotors should get hot and start "warping"; but the
> facts say otherwise, just as my intuition says that cellphones must be
> causing increased accident rates; but the facts say otherwise.

You tell that to the warped rotors I have discarded.
FWIW, when you machine rotor, you can actually *see* the warp right up
until they clean up.
>
> What I find most interesting is people blame me for their intuition being
> wrong, where they should blame evolution for giving humans the intuition of
> a monkey.
>
> BTW, with respect to the iKooks, what MARKETING does is play on intuition.
> Same with automotive fluids, brake pads, tires, and, yes, rotors.
>
> Intuition is a terrible thing for a whole bunch of reasons, the most
> important of which it is almost always wrong - but the next most important
> reason is that marketing preys on people's intuition.
>
> If marketing gold plates the letters on the marquee, people "think" it's
> better, or, more to the point, if a car simply has DTV caused by pad
> deposition, the shop tells them they need new rotors and pads (and maybe
> even new calipers and a few other things too).

I grew up and did my apprenticeship in a relatively poor area. You
couldn't suggest such expensive fixes to people , they couldn't afford
it. You were forced to do what was necessary to make the car serviceable
and *safe* to use.

> On the pads, if MARKETING throws in a spec of dust and calls it "ceramic"
> people think it too is better (they don't even know what the cold/hot
> friction ratings are as that is an unimportant detail to them - all that
> matters is that MARKETING called it "ceramic"), and if they put the word
> "performance" on a tire, people think it's better too.
>
> The list of false beliefs people own based on a hijack of their intuition
> by MARKETING probably will never end, at least until humans evolve further
> away from having the intuition necessary to grab a branch that is far away
> and intuit that it will hold up their bodies under the force of gravity.
>
> BTW, gravity is _another_ thing people intuit, where it doesn't even exist.
> But that's a topic for folks who have a background in space & time were
> we're moving in an orthogonal dimension to space at nearly the speed of
> light (which is felt by we monkeys as what we call the "force" of gravity).
>
> Anyway, I provided my references, and folks are welcome to read them.
> <https://ricksfreeautorepairadvice.com/warped-brake-rotors/>
> "Calling it brake rotor warp demonstrates a complete misunderstanding
>  of the metallurgy and the braking process"
>
> <https://trade.mechanic.com.au/news/solved-the-mystery-of-warped-brake-rotors>
>
> "Contrary to popular belief, brake rotors... don't warp, no matter  how
> aggressively a vehicle is driven."
>
> <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."

I never say that! Pedal pulsations can be caused by *hard spots* on
rotors. Warped disks are more likely to cause symptoms akin to a
*shimmy* in the steering under braking.
>
> <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."
>
> <https://www.buybrakes.com/help/why-do-brake-rotors-warp/>
>  "The thing is, rotors don't actually permanently warp."

That depends on the *actual cause*.
>
> If someone has a reliable reference that speaks of "warp" as if it really
> can happen, I'll read it, but rest assured, no reliable references will be
> found because it's impossible for rotors to do what people intuit they do.
>
> Doesn't matter if the rotor is solid or not, if they're sold in the USA,
> they meet a spec that makes it impossible - as the fluid would boil well
> before the rotor could get hot enough, and the rest of the brake system
> components would disintegrate well before the rotor ever got hot enough.

Hmmm, I only needed to replace my periphery melted rotor. Everything
else worked just as well as before and I didn't even get *brake fade*.
My intuition is telling me something.
>
> In summary, on the topic of rotor "warp", I'll read any reliable reference
> that people bring up to back up their intuition, but otherwise, there's no
> sense in this as it's like trying to explain to people that the earth isn't
> in the center of the solar system if they intuit otherwise and if they
> believe their own intuition far more than they believe in actual facts.
>
> Intuition is a terrible thing indeed.

--
Xeno

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