That's the part I don't buy Matt.  How fast are those rotors turning at
highway speed?  How does this deposit occur from one circumfrential location
to another?  If imprinting was as real a factor as this guy suggests, every
single car that has ever put a mile on a road would have suffered this after
the first stop at the end of a highway exit ramp.  It's a great sounding
theory for a guy's web site, but it's bull - at least as he presents it.

I've never mounted a rotor on a lathe as I never had a lathe.  I've
always used a dial indicator with the rotor on the car as that is THE
most accurate way to check for warp.  And thickness variation is checked
just as easily on a car as well.  And thickness variation would cause
much more severe pulsing anyway.  Warp just moves the calipers side to
side in their mount.  Since they are designed to move this way anyway,
this doesn't cause much problem.  The severe pulsing is caused from
variations in friction as the rotor turns and this is either from
variations in coefficient of friction around the circumference of the
rotor or from variations in clamping force around the circumference.
The former is caused by uneven pad material deposition or nonuniform
changes in the metal properties as described in the article.  The latter
is caused by uneven thickness of the rotor (also extremely rare).  Warp
just about never happens and even if it did, it would cause very slight
vibration and would NOT cause the car to shudder as will the other two
problems.

No problem, brain farts happen.  However, I have to admit when I hear
someone use the incorrect nomenclature it causes me to question the
veracity of their message.

Very little is required.  All it takes is enough to change the
coefficient of friction from one circumferential location to another.
One pad imprint can do it.  It is a little bit like oil.  It takes a
very thin film to radically change the coefficient of friction of a surface.

Matt

Matt - you get too hung up on little things and overlook the obvious.  Claim
what you will, but if you've never mounted and turned a rotor I'm not going
to spend any time arguing about what "could" be happening.  I'm happy to let
you believe what you read on a web site as the hidden answer to rotor
problems, and I'll simply bumble along fixing cars in my ignorance.  I'm
really not going to spend a lot of time trying to satisfy your needs for
empiracle evidence to refute something you read.

And I do stand corrected on this point, in that I should have said dial
indicator.  Don't know how the word caliper slipped in there unless it was
in the front of my mind - this being a brake discussion.  Regardless, if
you'd have worked on pulsing pedal problems you'd certainly have verified
warped rotors with an indicator.

Let me challenge that article this way Matt - how much depositing and
imprinting is necessary to cause a noticeable pulse in the pedal?  How much
to create wild pulsing at highway speed?  How  does this buildup occur in
such varying depths around a 10" disk that is turning at highway speeds with
(near) constant brake pressure, while 5 hard stops is all it takes to clean
it up?

A dial caliper can't easily measure run-out and a lathe doesn't measure
anything, so I basically don't believe you have ever checked a brake
rotor.  A caliper could measure thickness variation, but not warpage.  A
dial indicator in conjunction with a lathe could measure warpage, but
only if the rotor was installed true in the lathe and that wouldn't be
easy.  The least little off-axis mounting would look like warpage when
the lathe was spun.

Easiest is to just spin the rotor on the car with a magnetic mount dial
indicator.

Matt

Did you not read what I wrote?

Whatever you say.

No, they were not "verifiably" warped if you didn't measure them.

Except that rotors don't warp in general.  :-)

Matt

I too have "fixed" an occassional pulsing pedal this way, but it's the
exception.  That's not fixing a warped rotor which has many more times
proven the case for me.  Whether I tested them with a dial caliper or put
them on a lathe, they were verifiably warped.  It's very common with a lot
of the cheap aftermarket rotors out there.  Trying to make these rotors
better with brake cycles won't work.

It's ok to disagree - you know I'm fine with that.  I would only tweak your
closing comment by suggesting what I do - when faced with pulsing, first try
to clear the problem with braking techniques as you referenced.  When that
does not fix the problem, simple be aware that rotors do warp, and when
buying new don't go cheap.  Going better does not cost that much more but
works much better.  Good quality  rotors and ceramic pads.  And don't be
alarmed by warped rotors - it's more and more common as manufacturers
cheapen up the rotors they build with.

I haven't measured many with a dial indicator, but I've never yet found
one warped significantly.  And I've had a couple of "warped" rotors that
were "fixed" with 5-10 hard stops to redistribute the pad material.  A
mechanically warped disk would not get better with additional heating
cycles.

We'll have to agree to disagree.  However, I suggest that anyone who
thinks their disks are warped should take the time to check them with a
dial indicator.  I'll bet most times they will find no warpage.

Matt

I read that as well Matt.  Completely contradicts my experience.

If you have some data, I'm all ears.  However, until then, I believe
this gentleman...

http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

It also matches my experience.

Matt

Actually, a lot of aftermarket, and even some OEM rotors will warp from the
heat from semi-metallic pads.  The break-in stuff is more hyperbole than
reality, as is the theory of hard braking.  What really addresses this
problem best is a quality set of rotors and ceramic pads.

You may also want to check your driving habits and pad break-in
procedure as rotors rarely actually warp.  The pulsing is often a result
of uneven deposition of brake pad material onto the rotor.  This can
often be corrected with a few 5-10 really hard stops to heat up the
rotor and redistribute the material.  Also, try not to stop hard and
then hold the brakes for any period of time as that will cause pad
imprinting.  Try to let the car roll slowly ahead after a hard stop
rather than standing on the brakes afterward.

Matt

2008 sonat

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Don

I recently rented an almost new Camry and thought it was not onl
boring but dangerous.  This 4 cylinder had a hard time getting goin
if starting out on a small hill and the suspension is very soft an
wavy.  So I can understand why you are not happy with the Camry

I have a 2002 Sonata V6 and it has been a pretty good car and I a
hoping for 150K miles before the end.  It now has 74,000 miles on it
There is nothing major wrong with the car that I know of but littl
things are starting to malfunction like the gas door doesn't ope
when the switch is depressed

One big issue:  the brake rotors keep warping and Hyundai refuses t
fix them under warranty even though it was still covered under th
bumper-to-bumper.  That was a bad decision by Hyundai America.  
have now replaced the rotors and pads with high performance model
and hope that solves the problem

Next time I will buy a Honda which has yielded better performance an
reliability for me in the past. Good luck

no real problem. but wonder what you think about the 2007 & 2008 sonata
V6.  drive a camry and thinking about selling it and getting a 2007 or
2008 sonata V6. retired but work for hertz part time and of all the cars
we have in the $20000.00 to $25000.00 price range the sonata V6  is the
most fun to drive. handles great and lots and lots of power when you
need it with pretty good gas mileage. just wondered if you think the
sonata is on par with the camry and hold up in the long term. any real
problems  with the sonata or complaints from owners? my camry is a 2006
le 4cyl. great car but oh so  boring.   thanks   DAVE