Technical aspects of automobiles

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

I found out from another thread that brake rotors can’t warp and it seems
nobody on this planet can really (reliably) tell the difference between
brake friction materials (because there are no standards whatsoever)
according to
http://www.performanceoiltechnology.com/brakingsystems.htm

So, since I have horrible brake-induced wobble in my Toyota 4Runner, how
DOES anyone  buy the right parts given there are no regulations or
standards to protect us?

We may as well close our eyes and choose randomly for all the lack of
standards. Which leaves me to my most important question, having to trust
in your judgement and experience (which I don’t have).

Where would YOU buy a good quality rotors & pads for a Toyota 4Runner?

Stu

.
posted by admin in Без рубрики and have Comments (24)

24 Responses to “Can anyone tell the difference between rotors and pads (truthfully)?”

  1. admin says:

    "Hugo Schmeisser" <inva…@invalid.c0m> wrote in news:v–
    dndBXpOSYOJvZRVn…@magma.ca:

    >> I found out from another thread that brake rotors can’t warp
    > There are many causes of brake pedal pulsation.
    > http://www.babcox.com/editorial/bf/bf100326.htm

    Wow!
    That was the most excellent brake-pedal pulsation article I have ever
    seen.

    I had googled – but I hadn’t seen this article. I read it over and over
    and over. Thank you thank you thank you.  I learned quite a few new
    things today from that Babcox braking article.

    One is that I have been measuring runout all wrong! For example, I
    didn’t clean BEHIND the rotors before measuring the runout. And, I
    didn’t have the dial guage stem at an oblique angle to the rotor and
    pointing in the direction of rotartion (I had put it perpendicular)! The
    Babcox article suggests that the repeatable "blip" I experienced might
    be simply due to vibration induced by that erroneous perpendicular
    placement. The article also explained that thickness variation is
    generally the ultimate precursor of the severe high-speed brake pedal
    pulsation I’m experiencing. By thinking warped rotors, I was heading off
    in the wrong direction.

    Likewise with the friction material and rotor recommendations. Given
    there are no known friction material standards, and believing the
    performance oil article at
    http://www.performanceoiltechnology.com/brakingsystems.htm, I can come
    to the conclusion that one can’t believe the parts guy who says "these
    are ceramic", "these are semi metallic", etc. as it’s all just
    advertising!

    For example, the manufacturers can call the SAME friction material
    either:
     * Non Asbestos Organic Friction Material (NAO)
     * Semi-Metallic friction material
     * Low-Metallic friction material
     * Cerami-Metallic friction material
     * Corrector Lining
     * Euro-Met
       and more.

    Since all those names are for the same set of brake pads, it’s pretty
    clear the advertisers have had a field day with we poor mechanics.

    So, what am I going to do?

    1. Test runout again with the dial guage pointed at an angle and this
    time I will first remove the rotors, clean BEHIND the rotors, index the
    rotors by high spot and low spot and hub runout and torque down three of
    the six lug nuts, rotating three times to get the lowest runout.

    2. If runout is outside of 4Runner specifications (0.028 inches), I’ll
    purchase new rotors and pads and hardware (even though the pads are fine
    even after more than 50,000 miles).

    I’ll ONLY buy OEM pads and rotors (anything else seems like a gamble
    since there are no standards for the performance of those materials nor
    can we even believe simple material designations such as "ceramic" vs
    "metallic"). That really leaves nothing but OEM as the right choice.

    In general, I go Internet (remembering the punitive almost 9% uncle
    sam). For my 1988 Nissan Maxima, there is a great dealership in another
    state that all Nissan owners use who charges at least 20% to 40% less
    than any dealership (including shipping). There’s no other way to go for
    a Nissan as he’s truly the do it yourselfer’s friend so much more than
    the local dealership ever will be.

    Do Toyota home mechanics have a similar the-only-right-choice Internet-
    aware mechanic’s friend dealership like Nissan has?

  2. admin says:

    - Hide quoted text — Show quoted text -

    "hob" <dehob…@comcast.net> wrote in message news:…
    > "Stuart A. Bronstein" <spamt…@lexregia.com> wrote in message
    > news:FEwNf.36318$Jd.11501@newssvr25.news.prodigy.net…
    > > I found out from another thread that brake rotors can’t warp

    > Wrong – been certified as a brake expert in Federal and State courts,
    having
    > designed and built many kinds of brakes as well as brake testing machines
    > for Detroit and Japan, and have done hobby work on race cars for 35
    years –
    > rotors warp out of plane.
    >    And I have pulled off a fair number of rotor plates that were
    definitely
    > warped.

    > From your cite:

    > "The problem with this diagnosis and repair procedure is that first of all
    > is that brake rotors do not warp. "

    > Wrong.  They do, especially the ones that have offset bells. How can that
    be
    > if the website says it can’t?

    > Again, from your cite, as they state one sentence beyond where they say it
    > does not exist.:

    > "Brake rotor disc thickness variation or excessive lateral runout, as well
    > as drums that are out of round can cause vibrations and pulsations in the
    > brake pedal and/or steering wheel.  Brake lining material transfer onto
    the
    > rotor can also have an effect on this as well."

    > Check out what they said about the rotor in their excerpts above- "it’s
    not
    > warped, it really just has its faces warped out of plane"  yes, BS
    > doubletalk is what you saw on that site.
    >   " It’s not a duck, its really a mallard or its a bird with a green head
    > that has webbed feet and quacks":

    > 1) "Brake rotor disc thickness variation" means the planes of the rotor
    face
    > are no longer flat with reference to each other, and if beyond allowable
    > limits, each the face of the rotor has warped out of the permitted plane
    > with respect to each other.  That is called warp. (of the rotor face
    plane,
    > the part the shoes contact).

    > 2) "Excessive lateral runout" means the plane of the rotor face is no
    longer
    > in the range of allowed plane, when measured by a runout gauge mounted
    > externally to the rotor, and thus the face of the rotor has warped out of
    > permitted plane.
    >   (to make a runout measurement – mount rotor in trued solid axle, set
    > preloaded gauge on face, and turn rotor one turn while checking gauge to
    get
    > max and min: subtract to get total runout)
    >     "Excessive lateral runout" can be due to excessive "brake rotor disc
    > thickness variation" or bent mounts or twisted rotor.

    >   Rotors are made thin so they can be light and keep fleet/vehicle mpg
    down.
    > Even a first year engineering student can tell you how hard  braking with
    > the linkage turned hard over bends (warps) the rotor bell.
    >   (imagine 2 tons moving forward trying to go over a tire turned sideways
    > with the brake pads locked onto the rotor, a rotor designed for transfer
    of
    > force into floating claipers and transversely into the axle.
    >   Guess how the force gets from the 2 ton moving vehicle mass into the
    tire
    > tread in a turn– through the shoes gripping the rotor and back into the
    > axle – forces across the rotor plane, unlike straight ahead braking, where
    > the forces are in the rotor plane)

    >  Any experienced engineer will tell you that if there is a problem and it
    > goes way when you replace a part, the problem is gone.
    >   Was the problem the root cause and will it return? Well, if it wasn’t
    part
    > of the problem, the problem would still be there in some form.
    >    However, if it is only part of the problem, the problem will later
    > manifest the same symptoms (E.g, if the driver brakes hard in corners,
    part
    > of the problem, the rotors will again bend/wear the faces so that in time
    > the plane of the rotor surfaces are no longer within tolerance, Before the
    > driver got in and warped the new rotors, the new rotors were just fine)

    >  ( Logically, when you change the rotor and then the problem goes away,
    the
    > problem is gone.)

    > and it seems
    > > nobody on this planet can really (reliably) tell the difference between
    > > brake friction materials (because there are no standards whatsoever)
    > > according to
    > > http://www.performanceoiltechnology.com/brakingsystems.htm

    > the man ought to read the specs in the vehicle manuals, which do indeed
    list
    > tolerances for rotors. And he ought to get some in depth background first.
    >    The internet is full of half-aware self-promoters with partially
    applied
    > theories.    And AMSOIL, no less.

    > FWIW –  match mounting is a way to limit costly close tolerance machining
    in
    > many mating parts- you make hundreds of parts all alike, and then measure
    > them – some will be way off and get tossed, most will be within tolerance
    > and used according to their tolerance, and some may even be perfect.  It’s
    > cheaper than making each one perfect.

    > I’ll put this quote from them in here for the experienced engineers to get
    a
    > chcukle

    > "DTV is when the rotor thickness is not the same all the way around the
    > rotor. DTV is typically caused by lateral runout.  DTV can only be
    measured
    > with very specialized laboratory testing equipment or with special on
    > vehicle capacitance probes."

    > right…. ( or like a shop caliper or shop "mic", as noted in the
    > maintenance manuals.)

    >  Quote – "This [DTV] phenomenon is what many technicians refer to as
    > "warping", however they actually think the rotor warped and needs
    > replacement."

    >  OK, so what they are saying is that the rotor isn’t warped ( and so the
    > rotor is true?) and the face of the rotor plane has just warped, and so
    they
    > are saying that
    >    instead of the rotor needing replacing because the thickness varies,
    the
    > rotor needs replacing because the thickness varies and the esoteric DTV
    > measurements are lab things .(or you could just get refacing done at a
    brake
    > shop, if enough material is left).

    > enough of quoting their home-spun humor….

    > > So, since I have horrible brake-induced wobble in my Toyota 4Runner, how
    > > DOES anyone  buy the right parts given there are no regulations or
    > > standards to protect us?

    > There are regulations – Check out the following standards for brake
    > materials:  DE3A, BEEP,  NHTSA FMVSS-105

    > > We may as well close our eyes and choose randomly for all the lack of
    > > standards. Which leaves me to my most important question, having to
    trust
    > > in your judgement and experience (which I don’t have).

    > > Where would YOU buy a good quality rotors & pads for a Toyota 4Runner?

    > From Toyota –
    >   why?  aftermarket pads have few, if any standards.  New-car brake pads
    > (OEM) have to meet NHTSA standards, and thus actually do stop better, are
    > more reliable, and the dust around the kids and dogs is less hazardous.

    > nuff free stuff

    > > Stu

  3. admin says:

    Stuart A. Bronstein wrote:
    > I found out from another thread that brake rotors can’t warp and it seems
    > nobody on this planet can really (reliably) tell the difference between
    > brake friction materials (because there are no standards whatsoever)
    > according to
    > http://www.performanceoiltechnology.com/brakingsystems.htm

    I’ve never encountered that problem (telling pads from rotors).  The
    pads just seem to fit naturally inside the caliper.  And rotors seem to

    belong attached to an spindle or axle.  Never tried to interchange
    them.

    Sounds like you must have screwed up a brake job big time.  Maybe you
    shouldn’t try brake jobs in your driveway, but trust them to someone
    with the tools and knowlege.

    > So, since I have horrible brake-induced wobble in my Toyota 4Runner, how
    > DOES anyone  buy the right parts given there are no regulations or
    > standards to protect us?

    I’ve never had a problem using pads and rotors from the dealer, or from

    the local auto parts store (not one of those national chains).

    > We may as well close our eyes and choose randomly for all the lack of
    > standards. Which leaves me to my most important question, having to trust
    > in your judgement and experience (which I don’t have).

    Well, you may choose to close your eyes and buy something as important
    as brake parts from random sources, but I sure won’t.

    I have to ask…are you shilling for that oily website listed above?

  4. admin says:

    hob wrote:
    > > Even a first year engineering student can tell you how hard  braking with
    > > the linkage turned hard over bends (warps) the rotor bell.

    That’s just plain silly.

    > >   (imagine 2 tons moving forward trying to go over a tire turned sideways
    > > with the brake pads locked onto the rotor, a rotor designed for transfer
    > of
    > > force into floating claipers and transversely into the axle.

    The caliper can move freely from side to side (floating calipers). There
    is no side load at all due to steering.

    > >   Guess how the force gets from the 2 ton moving vehicle mass into the
    > tire
    > > tread in a turn– through the shoes gripping the rotor and back into the
    > > axle – forces across the rotor plane, unlike straight ahead braking, where
    > > the forces are in the rotor plane)

    This is fantasy. The wheel is mounted solid to the axle with the rotor
    sandwiched between. Even if the axle would deflect it couldn’t possibly
    deflect enough to exceed the side travel of the calipers. If the car is
    sliding sideways the brakes see no load at all because there would be no
    force to turn the wheels.
            Heat build up is usually what causes rotors to warp. You don’t even
    have to put the rotor on a car just toss it in a fire and it will warp.
    Rust in the ventilation passages can also warp rotors. And frozen
    calipers can also warp rotors – not so much because of uneven force
    loads but uneven heat loads.

    > >  Any experienced engineer will tell you that if there is a problem and it
    > > goes way when you replace a part, the problem is gone.
    > >   Was the problem the root cause and will it return? Well, if it wasn’t
    > part
    > > of the problem, the problem would still be there in some form.
    > >    However, if it is only part of the problem, the problem will later
    > > manifest the same symptoms (E.g, if the driver brakes hard in corners,
    > part
    > > of the problem, the rotors will again bend/wear the faces so that in time
    > > the plane of the rotor surfaces are no longer within tolerance, Before the
    > > driver got in and warped the new rotors, the new rotors were just fine)

    This is nonsense. Excessive braking can result in warped rotors, but
    braking on turns has nothing to do with it.

    -jim

    - Hide quoted text — Show quoted text -

    > >  ( Logically, when you change the rotor and then the problem goes away,
    > the
    > > problem is gone.)

    > > and it seems
    > > > nobody on this planet can really (reliably) tell the difference between
    > > > brake friction materials (because there are no standards whatsoever)
    > > > according to
    > > > http://www.performanceoiltechnology.com/brakingsystems.htm

    > > the man ought to read the specs in the vehicle manuals, which do indeed
    > list
    > > tolerances for rotors. And he ought to get some in depth background first.
    > >    The internet is full of half-aware self-promoters with partially
    > applied
    > > theories.    And AMSOIL, no less.

    > > FWIW –  match mounting is a way to limit costly close tolerance machining
    > in
    > > many mating parts- you make hundreds of parts all alike, and then measure
    > > them – some will be way off and get tossed, most will be within tolerance
    > > and used according to their tolerance, and some may even be perfect.  It’s
    > > cheaper than making each one perfect.

    > > I’ll put this quote from them in here for the experienced engineers to get
    > a
    > > chcukle

    > > "DTV is when the rotor thickness is not the same all the way around the
    > > rotor. DTV is typically caused by lateral runout.  DTV can only be
    > measured
    > > with very specialized laboratory testing equipment or with special on
    > > vehicle capacitance probes."

    > > right…. ( or like a shop caliper or shop "mic", as noted in the
    > > maintenance manuals.)

    > >  Quote – "This [DTV] phenomenon is what many technicians refer to as
    > > "warping", however they actually think the rotor warped and needs
    > > replacement."

    > >  OK, so what they are saying is that the rotor isn’t warped ( and so the
    > > rotor is true?) and the face of the rotor plane has just warped, and so
    > they
    > > are saying that
    > >    instead of the rotor needing replacing because the thickness varies,
    > the
    > > rotor needs replacing because the thickness varies and the esoteric DTV
    > > measurements are lab things .(or you could just get refacing done at a
    > brake
    > > shop, if enough material is left).

    > > enough of quoting their home-spun humor….

    > > > So, since I have horrible brake-induced wobble in my Toyota 4Runner, how
    > > > DOES anyone  buy the right parts given there are no regulations or
    > > > standards to protect us?

    > > There are regulations – Check out the following standards for brake
    > > materials:  DE3A, BEEP,  NHTSA FMVSS-105

    > > > We may as well close our eyes and choose randomly for all the lack of
    > > > standards. Which leaves me to my most important question, having to
    > trust
    > > > in your judgement and experience (which I don’t have).

    > > > Where would YOU buy a good quality rotors & pads for a Toyota 4Runner?

    > > From Toyota –
    > >   why?  aftermarket pads have few, if any standards.  New-car brake pads
    > > (OEM) have to meet NHTSA standards, and thus actually do stop better, are
    > > more reliable, and the dust around the kids and dogs is less hazardous.

    > > nuff free stuff

    > > > Stu

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  5. admin says:

    "Hugo Schmeisser" <inva…@invalid.c0m> wrote in news:762dnaOjgI7dBprZRVn-
    i…@magma.ca:

    >> Do Toyota home mechanics have a similar the-only-right-choice
    >> Internet- aware mechanic’s friend dealership?
    > This is the only one I’m personally aware of:
    > http://www.1sttoyotaparts.com/

    Hello Hugo,
    Time and time again, you’re the voice of reason with answers!

    I checked prices today for new OEM rotors & I was amazed at the results!
    I called three local dealers and a half dozen Internet suppliers.
    Predictably, the dealers were at list or above list ($107 per rotor).
    One local Toyota dealer was way off base at $123 per OEM rotor.

    Likewise the lowest Internet dealership was about $72 dollars.
    But a few were at or near the local dealers’ prices for OEM rotors.

    The http://www.1sttoyotaparts.com was close (at $76 dollars) to the lowest price.
    So, I now have my two preferred Internet-aware Toyota dealers that I can
    now deal with forever without having to perform much further research (I
    want to keep THEM in business by giving them my business!).

    Thanks for being the voice of reason and answering the question asked.
    Because of you, we now have a good answer for everyone!

    Stu

  6. admin says:

    > This is nonsense. Excessive braking can result in warped rotors, but
    > braking on turns has nothing to do with it.

    According to this article (probably the best on the Internet)
    http://www.babcox.com/editorial/bf/bf100326.htm

    "Many technicians are under the impression that a "warped" rotor is one
    that has too much runout. They also attribute this "warping" to why the
    brake pedal pulsates. This is not true. Runout will NOT cause pedal
    pulsation in most cases."

    So, I’m back to being confused about whether or not brake rotor
    pulsation is really caused by "warped" rotors or not. It seems not.

    But we learn more every day about brakes so time will tell for all.
    Stu

    jim <"sjedgingN0sp"@m…@mwt.net> wrote in
    news:1141434475_67@sp6iad.superfeed.net:

    - Hide quoted text — Show quoted text -

    > hob wrote:

    >> > Even a first year engineering student can tell you how hard
    >> > braking with the linkage turned hard over bends (warps) the rotor
    >> > bell.

    > That’s just plain silly.

    >> >   (imagine 2 tons moving forward trying to go over a tire turned
    >> >   sideways
    >> > with the brake pads locked onto the rotor, a rotor designed for
    >> > transfer
    >> of
    >> > force into floating claipers and transversely into the axle.

    > The caliper can move freely from side to side (floating calipers).
    > There is no side load at all due to steering.

    >> >   Guess how the force gets from the 2 ton moving vehicle mass into
    >> >   the
    >> tire
    >> > tread in a turn– through the shoes gripping the rotor and back
    >> > into the axle – forces across the rotor plane, unlike straight
    >> > ahead braking, where the forces are in the rotor plane)

    > This is fantasy. The wheel is mounted solid to the axle with the rotor
    > sandwiched between. Even if the axle would deflect it couldn’t
    > possibly deflect enough to exceed the side travel of the calipers. If
    > the car is sliding sideways the brakes see no load at all because
    > there would be no force to turn the wheels.
    >      Heat build up is usually what causes rotors to warp. You don’t
    >      even
    > have to put the rotor on a car just toss it in a fire and it will
    > warp. Rust in the ventilation passages can also warp rotors. And
    > frozen calipers can also warp rotors – not so much because of uneven
    > force loads but uneven heat loads.

    >> >  Any experienced engineer will tell you that if there is a problem
    >> >  and it
    >> > goes way when you replace a part, the problem is gone.
    >> >   Was the problem the root cause and will it return? Well, if it
    >> >   wasn’t
    >> part
    >> > of the problem, the problem would still be there in some form.
    >> >    However, if it is only part of the problem, the problem will
    >> >    later
    >> > manifest the same symptoms (E.g, if the driver brakes hard in
    >> > corners,
    >> part
    >> > of the problem, the rotors will again bend/wear the faces so that
    >> > in time the plane of the rotor surfaces are no longer within
    >> > tolerance, Before the driver got in and warped the new rotors, the
    >> > new rotors were just fine)

    > This is nonsense. Excessive braking can result in warped rotors, but
    > braking on turns has nothing to do with it.

    > -jim

    >> >  ( Logically, when you change the rotor and then the problem goes
    >> >  away,
    >> the
    >> > problem is gone.)

    >> > and it seems
    >> > > nobody on this planet can really (reliably) tell the difference
    >> > > between brake friction materials (because there are no standards
    >> > > whatsoever) according to
    >> > > http://www.performanceoiltechnology.com/brakingsystems.htm

    >> > the man ought to read the specs in the vehicle manuals, which do
    >> > indeed
    >> list
    >> > tolerances for rotors. And he ought to get some in depth background
    >> > first.
    >> >    The internet is full of half-aware self-promoters with partially
    >> applied
    >> > theories.    And AMSOIL, no less.

    >> > FWIW –  match mounting is a way to limit costly close tolerance
    >> > machining
    >> in
    >> > many mating parts- you make hundreds of parts all alike, and then
    >> > measure them – some will be way off and get tossed, most will be
    >> > within tolerance and used according to their tolerance, and some
    >> > may even be perfect.  It’s cheaper than making each one perfect.

    >> > I’ll put this quote from them in here for the experienced engineers
    >> > to get
    >> a
    >> > chcukle

    >> > "DTV is when the rotor thickness is not the same all the way around
    >> > the rotor. DTV is typically caused by lateral runout.  DTV can only
    >> > be
    >> measured
    >> > with very specialized laboratory testing equipment or with special
    >> > on vehicle capacitance probes."

    >> > right…. ( or like a shop caliper or shop "mic", as noted in the
    >> > maintenance manuals.)

    >> >  Quote – "This [DTV] phenomenon is what many technicians refer to
    >> >  as
    >> > "warping", however they actually think the rotor warped and needs
    >> > replacement."

    >> >  OK, so what they are saying is that the rotor isn’t warped ( and
    >> >  so the
    >> > rotor is true?) and the face of the rotor plane has just warped,
    >> > and so
    >> they
    >> > are saying that
    >> >    instead of the rotor needing replacing because the thickness
    >> >    varies,
    >> the
    >> > rotor needs replacing because the thickness varies and the esoteric
    >> > DTV measurements are lab things .(or you could just get refacing
    >> > done at a
    >> brake
    >> > shop, if enough material is left).

    >> > enough of quoting their home-spun humor….

    >> > > So, since I have horrible brake-induced wobble in my Toyota
    >> > > 4Runner, how DOES anyone  buy the right parts given there are no
    >> > > regulations or standards to protect us?

    >> > There are regulations – Check out the following standards for brake
    >> > materials:  DE3A, BEEP,  NHTSA FMVSS-105

    >> > > We may as well close our eyes and choose randomly for all the
    >> > > lack of standards. Which leaves me to my most important question,
    >> > > having to
    >> trust
    >> > > in your judgement and experience (which I don’t have).

    >> > > Where would YOU buy a good quality rotors & pads for a Toyota
    >> > > 4Runner?

    >> > From Toyota –
    >> >   why?  aftermarket pads have few, if any standards.  New-car brake
    >> >   pads
    >> > (OEM) have to meet NHTSA standards, and thus actually do stop
    >> > better, are more reliable, and the dust around the kids and dogs is
    >> > less hazardous.

    >> > nuff free stuff

    >> > > Stu

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  7. admin says:

    Steve <n…@spam.thanks> wrote in news:GtGdnQg7oIAmUJXZ4p2dnA@texas.net:

    >> how DOES anyone  buy the right parts given there are no regulations
    >> or standards to protect us?

    > Buy from a reputable vendor who carries reputable brands (Bendix,
    > Raybestos, etc.)

    Easier said than done.

    It was already shown that the manufacturers of aftermarket parts don’t have
    to follow any standards (not even FMVSS 105 & FMVSS 135 braking performance
    standards).

    Worse, they don’t even have to follow naming conventions (eg ceramics and
    semi-metallics are the same pads if they want them to be called that).

    Even a reputable Ford dealership sells crappy Pinto’s in addition to the
    good cars and so does the "reputable vendor".

    The only real solution is to know what we’re buying; and it seems that the
    only way to really know what we’re buying is to go OEM.

    There is no other way is what I’ve concluded after a week’s worth of
    research to the contrary.

    Stu

  8. admin says:

    "hob" <dehob…@comcast.net> wrote in
    news:v5Sdnf-LU7B5LpXZnZ2dnUVZ_v6dnZ2d@comcast.com:

    > From your cite:
    > "The problem with this diagnosis and repair procedure is that first of
    > all is that brake rotors do not warp. "

    Hi Hob,

    Thanks for the wonderful detail to help all of us learn more to truly
    understand and accurately diagnose the real cause of brake shudder.

    In a way, I’m sorry I referred to that one article which said brake
    rotors don’t warp
    (http://www.performanceoiltechnology.com/brakingsystems.htm) because
    other items in that article make us suspect they’re biased somewhat.

    However, this expert article is probably the best treatise on automotive
    brake pedal pulsation causes on the entire Internet
    (http://www.babcox.com/editorial/bf/bf100326.htm) which basically says
    the same thing!

    …."Many technicians are under the impression that a "warped" rotor is
    one that has too much runout. They also attribute this "warping" to why
    the brake pedal pulsates. This is not true…."

    So, just like we can’t get colds & flu from being cold & wet (yet every
    mom & pop out there thinks we do), brake rotors (apparently) don’t warp,
    yet every do it yourself garage mechanic thinks they do.

    I’m glad we can have this dialog to help all of us (me included) better
    understand the cause and effect of brake pedal pulsation at high speed.

    Stu

    "hob" <dehob…@comcast.net> wrote in
    news:v5Sdnf-LU7B5LpXZnZ2dnUVZ_v6dnZ2d@comcast.com:

    - Hide quoted text — Show quoted text -

    > "Stuart A. Bronstein" <spamt…@lexregia.com> wrote in message
    > news:FEwNf.36318$Jd.11501@newssvr25.news.prodigy.net…
    >> I found out from another thread that brake rotors can’t warp

    > Been certified as a brake expert in Federal and State courts,
    > having designed and built many kinds of brakes as well as brake
    > testing machines for Detroit and Japan, and have done hobby work on
    > race cars for 35 years – rotors warp out of plane.
    >    And I have pulled off a fair number of rotor plates that were
    >    definitely
    > warped.

    > From your cite:

    > "The problem with this diagnosis and repair procedure is that first of
    > all is that brake rotors do not warp. "

    > Wrong.  They do, especially the ones that have offset bells. How can
    > that be if the website says it can’t?

    > Again, from your cite, as they state one sentence beyond where they
    > say it does not exist.:

    > "Brake rotor disc thickness variation or excessive lateral runout, as
    > well as drums that are out of round can cause vibrations and
    > pulsations in the brake pedal and/or steering wheel.  Brake lining
    > material transfer onto the rotor can also have an effect on this as
    > well."

    > Check out what they said about the rotor in their excerpts above-
    > "it’s not warped, it really just has its faces warped out of plane"
    > yes, BS doubletalk is what you saw on that site.
    >   " It’s not a duck, its really a mallard or its a bird with a green
    >   head
    > that has webbed feet and quacks":

    > 1) "Brake rotor disc thickness variation" means the planes of the
    > rotor face are no longer flat with reference to each other, and if
    > beyond allowable limits, each the face of the rotor has warped out of
    > the permitted plane with respect to each other.  That is called warp.
    > (of the rotor face plane, the part the shoes contact).

    > 2) "Excessive lateral runout" means the plane of the rotor face is no
    > longer in the range of allowed plane, when measured by a runout gauge
    > mounted externally to the rotor, and thus the face of the rotor has
    > warped out of permitted plane.
    >   (to make a runout measurement – mount rotor in trued solid axle, set
    > preloaded gauge on face, and turn rotor one turn while checking gauge
    > to get max and min: subtract to get total runout)
    >     "Excessive lateral runout" can be due to excessive "brake rotor
    >     disc
    > thickness variation" or bent mounts or twisted rotor.

    >   Rotors are made thin so they can be light and keep fleet/vehicle mpg
    >   down.
    > Even a first year engineering student can tell you how hard  braking
    > with the linkage turned hard over bends (warps) the rotor bell.
    >   (imagine 2 tons moving forward trying to go over a tire turned
    >   sideways
    > with the brake pads locked onto the rotor, a rotor designed for
    > transfer of force into floating claipers and transversely into the
    > axle.
    >   Guess how the force gets from the 2 ton moving vehicle mass into the
    >   tire
    > tread in a turn– through the shoes gripping the rotor and back into
    > the axle – forces across the rotor plane, unlike straight ahead
    > braking, where the forces are in the rotor plane)

    >  Any experienced engineer will tell you that if there is a problem and
    >  it
    > goes way when you replace a part, the problem is gone.
    >   Was the problem the root cause and will it return? Well, if it
    >   wasn’t part
    > of the problem, the problem would still be there in some form.
    >    However, if it is only part of the problem, the problem will later
    > manifest the same symptoms (E.g, if the driver brakes hard in corners,
    > part of the problem, the rotors will again bend/wear the faces so that
    > in time the plane of the rotor surfaces are no longer within
    > tolerance, Before the driver got in and warped the new rotors, the new
    > rotors were just fine)

    >  ( Logically, when you change the rotor and then the problem goes
    >  away, the
    > problem is gone.)

    > and it seems
    >> nobody on this planet can really (reliably) tell the difference
    >> between brake friction materials (because there are no standards
    >> whatsoever) according to
    >> http://www.performanceoiltechnology.com/brakingsystems.htm

    > the man ought to read the specs in the vehicle manuals, which do
    > indeed list tolerances for rotors. And he ought to get some in depth
    > background first.
    >    The internet is full of half-aware self-promoters with partially
    >    applied
    > theories.    And AMSOIL, no less.

    > FWIW –  match mounting is a way to limit costly close tolerance
    > machining in many mating parts- you make hundreds of parts all alike,
    > and then measure them – some will be way off and get tossed, most will
    > be within tolerance and used according to their tolerance, and some
    > may even be perfect.  It’s cheaper than making each one perfect.

    > I’ll put this quote from them in here for the experienced engineers to
    > get a chcukle

    > "DTV is when the rotor thickness is not the same all the way around
    > the rotor. DTV is typically caused by lateral runout.  DTV can only be
    > measured with very specialized laboratory testing equipment or with
    > special on vehicle capacitance probes."

    > right…. ( or like a shop caliper or shop "mic", as noted in the
    > maintenance manuals.)

    >  Quote – "This [DTV] phenomenon is what many technicians refer to as
    > "warping", however they actually think the rotor warped and needs
    > replacement."

    >  OK, so what they are saying is that the rotor isn’t warped ( and so
    >  the
    > rotor is true?) and the face of the rotor plane has just warped, and
    > so they are saying that
    >    instead of the rotor needing replacing because the thickness
    >    varies, the
    > rotor needs replacing because the thickness varies and the esoteric
    > DTV measurements are lab things .(or you could just get refacing done
    > at a brake shop, if enough material is left).

    > enough of quoting their home-spun humor….

    >> So, since I have horrible brake-induced wobble in my Toyota 4Runner,
    >> how DOES anyone  buy the right parts given there are no regulations
    >> or standards to protect us?

    > There are regulations – Check out the following standards for brake
    > materials:  DE3A, BEEP,  NHTSA FMVSS-105

    >> We may as well close our eyes and choose randomly for all the lack of
    >> standards. Which leaves me to my most important question, having to
    >> trust in your judgement and experience (which I don’t have).

    >> Where would YOU buy a good quality rotors & pads for a Toyota
    >> 4Runner?

    > From Toyota –
    >   why?  aftermarket pads have few, if any standards.  New-car brake
    >   pads
    > (OEM) have to meet NHTSA standards, and thus actually do stop better,
    > are more reliable, and the dust around the kids and dogs is less
    > hazardous.

    > nuff free stuff

    >> Stu

  9. admin says:

    "Stuart A. Bronstein" wrote:

    > > This is nonsense. Excessive braking can result in warped rotors, but
    > > braking on turns has nothing to do with it.

    > According to this article (probably the best on the Internet)
    > http://www.babcox.com/editorial/bf/bf100326.htm

    > "Many technicians are under the impression that a "warped" rotor is one
    > that has too much runout. They also attribute this "warping" to why the
    > brake pedal pulsates. This is not true. Runout will NOT cause pedal
    > pulsation in most cases."

    This is sort of true but misleading. If the 2 sides of the disc stay
    parallel, there won’t be any pulsation even if there is warpage. This
    may often be the case when the runout is small. Most rotors have
    ventilation slots between the disc surfaces this makes it unlikely that
    the surfaces stay nice and parallel when the warp is large.
            If you have pulsation when braking on dry pavement then it is coming
    from the disks not running true. This can develop in numerous ways. For
    instance due to impurities in the metal or other reasons part of the
    disk surface can become much harder than the rest. As a result the disk
    will wear unevenly. Now you might choose to not call this "warping", but
    the result is the same the disc surface doesn’t run true and causes
    pulsation in the brake pedal.

    > So, I’m back to being confused about whether or not brake rotor
    > pulsation is really caused by "warped" rotors or not. It seems not.

     Excluding pulsation due to ABS and malfunctioning ABS the only thing
    that can cause pulsation in the brake pedal is a disk or drum that is
    not running true. Stuck calipers can greatly magnify a small amount of
    runout in a disk. So the problem may be more than the runout. But if the
    discs/drums are running perfectly true you won’t have any pulsation in
    the pedal.

            And incidentally, brake shudder and pulsation in the brake pedal are
    not the same thing. If everything besides the rotors are generally in
    good condition you can have a pulsation in the brake pedal alone. That
    is, a passenger wouldn’t notice anything at all. If you get a shudder
    when you hit the brakes it may also be felt in the brake pedal or it
    might not. A shudder or vibration might not even be a brake problem or
    only partly a brake problem. Bad suspension components, out of balance
    tires or out of round tires could all cause a vibration that is
    triggered by applying the brakes. It is possible to have a condition
    where the whole car shakes violently when the brakes are applied without
    any pulsation in the brake pedal.

    -jim

    -jim

    -jim

    - Hide quoted text — Show quoted text -

    > But we learn more every day about brakes so time will tell for all.
    > Stu

    > jim <"sjedgingN0sp"@m…@mwt.net> wrote in
    > news:1141434475_67@sp6iad.superfeed.net:

    > > hob wrote:

    > >> > Even a first year engineering student can tell you how hard
    > >> > braking with the linkage turned hard over bends (warps) the rotor
    > >> > bell.

    > > That’s just plain silly.

    > >> >   (imagine 2 tons moving forward trying to go over a tire turned
    > >> >   sideways
    > >> > with the brake pads locked onto the rotor, a rotor designed for
    > >> > transfer
    > >> of
    > >> > force into floating claipers and transversely into the axle.

    > > The caliper can move freely from side to side (floating calipers).
    > > There is no side load at all due to steering.

    > >> >   Guess how the force gets from the 2 ton moving vehicle mass into
    > >> >   the
    > >> tire
    > >> > tread in a turn– through the shoes gripping the rotor and back
    > >> > into the axle – forces across the rotor plane, unlike straight
    > >> > ahead braking, where the forces are in the rotor plane)

    > > This is fantasy. The wheel is mounted solid to the axle with the rotor
    > > sandwiched between. Even if the axle would deflect it couldn’t
    > > possibly deflect enough to exceed the side travel of the calipers. If
    > > the car is sliding sideways the brakes see no load at all because
    > > there would be no force to turn the wheels.
    > >      Heat build up is usually what causes rotors to warp. You don’t
    > >      even
    > > have to put the rotor on a car just toss it in a fire and it will
    > > warp. Rust in the ventilation passages can also warp rotors. And
    > > frozen calipers can also warp rotors – not so much because of uneven
    > > force loads but uneven heat loads.

    > >> >  Any experienced engineer will tell you that if there is a problem
    > >> >  and it
    > >> > goes way when you replace a part, the problem is gone.
    > >> >   Was the problem the root cause and will it return? Well, if it
    > >> >   wasn’t
    > >> part
    > >> > of the problem, the problem would still be there in some form.
    > >> >    However, if it is only part of the problem, the problem will
    > >> >    later
    > >> > manifest the same symptoms (E.g, if the driver brakes hard in
    > >> > corners,
    > >> part
    > >> > of the problem, the rotors will again bend/wear the faces so that
    > >> > in time the plane of the rotor surfaces are no longer within
    > >> > tolerance, Before the driver got in and warped the new rotors, the
    > >> > new rotors were just fine)

    > > This is nonsense. Excessive braking can result in warped rotors, but
    > > braking on turns has nothing to do with it.

    > > -jim

    > >> >  ( Logically, when you change the rotor and then the problem goes
    > >> >  away,
    > >> the
    > >> > problem is gone.)

    > >> > and it seems
    > >> > > nobody on this planet can really (reliably) tell the difference
    > >> > > between brake friction materials (because there are no standards
    > >> > > whatsoever) according to
    > >> > > http://www.performanceoiltechnology.com/brakingsystems.htm

    > >> > the man ought to read the specs in the vehicle manuals, which do
    > >> > indeed
    > >> list
    > >> > tolerances for rotors. And he ought to get some in depth background
    > >> > first.
    > >> >    The internet is full of half-aware self-promoters with partially
    > >> applied
    > >> > theories.    And AMSOIL, no less.

    > >> > FWIW –  match mounting is a way to limit costly close tolerance
    > >> > machining
    > >> in
    > >> > many mating parts- you make hundreds of parts all alike, and then
    > >> > measure them – some will be way off and get tossed, most will be
    > >> > within tolerance and used according to their tolerance, and some
    > >> > may even be perfect.  It’s cheaper than making each one perfect.

    > >> > I’ll put this quote from them in here for the experienced engineers
    > >> > to get
    > >> a
    > >> > chcukle

    > >> > "DTV is when the rotor thickness is not the same all the way around
    > >> > the rotor. DTV is typically caused by lateral runout.  DTV can only
    > >> > be
    > >> measured
    > >> > with very specialized laboratory testing equipment or with special
    > >> > on vehicle capacitance probes."

    > >> > right…. ( or like a shop caliper or shop "mic", as noted in the
    > >> > maintenance manuals.)

    > >> >  Quote – "This [DTV] phenomenon is what many technicians refer to
    > >> >  as
    > >> > "warping", however they actually think the rotor warped and needs
    > >> > replacement."

    > >> >  OK, so what they are saying is that the rotor isn’t warped ( and
    > >> >  so the
    > >> > rotor is true?) and the face of the rotor plane has just warped,
    > >> > and so
    > >> they
    > >> > are saying that
    > >> >    instead of the rotor needing replacing because the thickness
    > >> >    varies,
    > >> the
    > >> > rotor needs replacing because the thickness varies and the esoteric
    > >> > DTV measurements are lab things .(or you could just get refacing
    > >> > done at a
    > >> brake
    > >> > shop, if enough material is left).

    > >> > enough of quoting their home-spun humor….

    > >> > > So, since I have horrible brake-induced wobble in my Toyota
    > >> > > 4Runner, how DOES anyone  buy the right parts given there are no
    > >> > > regulations or standards to protect us?

    > >> > There are regulations – Check out the following standards for brake
    > >> > materials:  DE3A, BEEP,  NHTSA FMVSS-105

    > >> > > We may as well close our eyes and choose randomly for all the
    > >> > > lack of standards. Which leaves me to my most important question,
    > >> > > having to
    > >> trust
    > >> > > in your judgement and experience (which I don’t have).

    > >> > > Where would YOU buy a good quality rotors & pads for a Toyota
    > >> > > 4Runner?

    > >> > From Toyota –
    > >> >   why?  aftermarket pads have few, if any standards.  New-car brake
    > >> >   pads
    > >> > (OEM) have to meet NHTSA standards, and thus actually do stop
    > >> > better, are more reliable, and the dust around the kids and dogs is
    > >> > less hazardous.

    > >> > nuff free stuff

    > >> > > Stu

    > > —-== Posted via Newsfeeds.Com – Unlimited-Unrestricted-Secure Usenet
    > > News==—- http://www.newsfeeds.com The #1 Newsgroup Service in the
    > > World! 120,000+ Newsgroups —-= East and West-Coast Server Farms –
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  10. admin says:

    "Stuart A. Bronstein" <spamt…@lexregia.com> wrote in message
    news:nvaOf.43710$H71.22542@newssvr13.news.prodigy.com…

    > > This is nonsense. Excessive braking can result in warped rotors, but
    > > braking on turns has nothing to do with it.

    > According to this article (probably the best on the Internet)
    > http://www.babcox.com/editorial/bf/bf100326.htm

    > "Many technicians are under the impression that a "warped" rotor is one
    > that has too much runout. They also attribute this "warping" to why the
    > brake pedal pulsates. This is not true. Runout will NOT cause pedal
    > pulsation in most cases."

    Runout WILL cause pulsation.  Even though the caliper is free to move, it
    has mass, and to move it takes energy.  The quicker it has to move, the more
    pronounced is the effect. Force is still equal to mass time acceleration.

    And you WILL feel it in the pedal.  And by truing the rotor, it will go
    away.

    And when you get some idiot with a torque stick/torque wrench installing
    a wheel, WILL likely return.

  11. admin says:

    On Sat, 04 Mar 2006 06:31:47 GMT, "Stuart A. Bronstein"

    - Hide quoted text — Show quoted text -

    <spamt…@lexregia.com> wrote:
    >> This is nonsense. Excessive braking can result in warped rotors, but
    >> braking on turns has nothing to do with it.

    >According to this article (probably the best on the Internet)
    >http://www.babcox.com/editorial/bf/bf100326.htm

    >"Many technicians are under the impression that a "warped" rotor is one
    >that has too much runout. They also attribute this "warping" to why the
    >brake pedal pulsates. This is not true. Runout will NOT cause pedal
    >pulsation in most cases."

    >So, I’m back to being confused about whether or not brake rotor
    >pulsation is really caused by "warped" rotors or not. It seems not.

    >But we learn more every day about brakes so time will tell for all.
    >Stu

    Confused?  Why?  Fucking take your car in and have the rotors
    machined, and when the pulsation stops, you can fucking bet it is
    because the pads now have a flat surface to grip.

    *************************
    Dave

  12. admin says:

    "Stuart A. Bronstein" <spamt…@lexregia.com> wrote in
    news:nvaOf.43710$H71.22542@newssvr13.news.prodigy.com:

    >> This is nonsense. Excessive braking can result in warped rotors, but
    >> braking on turns has nothing to do with it.

    > According to this article (probably the best on the Internet)
    > http://www.babcox.com/editorial/bf/bf100326.htm

    > "Many technicians are under the impression that a "warped" rotor is
    > one that has too much runout. They also attribute this "warping" to
    > why the brake pedal pulsates. This is not true. Runout will NOT cause
    > pedal pulsation in most cases."

    > So, I’m back to being confused about whether or not brake rotor
    > pulsation is really caused by "warped" rotors or not. It seems not.

    > But we learn more every day about brakes so time will tell for all.

    If that is the best on the web then it must be true.

    Well, no it isn’t.

    In a perfect world a warped rotor would not cause pulsations.

    However, a warped rotor will rapidly wear at the high spots (wear tends
    to occur in brakes off position), which will rapidly create DTV (Disc
    thickness variation) which will cause BTV (brake torque variation) even
    in a perfect car.

    But, the callipers don’t slide smoothly in the real world, so I suspect
    you’ll pick up a warped rotor via the pedal  even if there is no DTV.

    So, now you can get them to correct that article.

    Cheers

    Greg Locock

  13. admin says:

    DTJ <n…@nowhere.com> wrote in news:g17k02pllgnipo1po1p6o9u9olc54hkj4o@
    4ax.com:

    >>According to this article (probably the best on the Internet)
    >>http://www.babcox.com/editorial/bf/bf100326.htm

    >>"Many technicians … attribute "warping" to why the
    >>brake pedal pulsates. This is not true.
    > Confused?  Why?  Fucking take your car in and have the rotors
    > machined, and when the pulsation stops, you can fucking bet it is
    > because the pads now have a flat surface to grip.

    Hi Dave,

    According to more than one well-informed article, that’s exactly what most
    technicians do, and, that’s exactly the wrong approach.
     http://www.babcox.com/editorial/bf/bf100326.htm

    I am just looking to find the proper way to resolve this problem long term
    and, just the uneducated technician who thinks high octane gas is "better"
    gas, there’s a lot of ignorance posing as fact out there.

    I’m simply trying to properly diagnose, isolate, and repair my first case
    of brake pedal pulsation at highway speeds on a Toyota 4Runner truck.

    I’m realizing neither machining the rotors nor simply replacing them will
    solve the problem, long term. I’m getting closer to the answer though, with
    your help, and I hope those who read this thread in the future benefit.

    Stu

  14. admin says:

    Stuart A. Bronstein wrote:

    snip

    - Hide quoted text — Show quoted text -

    > According to more than one well-informed article, that’s exactly what
    > most technicians do, and, that’s exactly the wrong approach.
    > http://www.babcox.com/editorial/bf/bf100326.htm

    > I am just looking to find the proper way to resolve this problem long
    > term and, just the uneducated technician who thinks high octane gas
    > is "better" gas, there’s a lot of ignorance posing as fact out there.

    > I’m simply trying to properly diagnose, isolate, and repair my first
    > case of brake pedal pulsation at highway speeds on a Toyota 4Runner
    > truck.

    > I’m realizing neither machining the rotors nor simply replacing them
    > will solve the problem, long term. I’m getting closer to the answer
    > though, with your help, and I hope those who read this thread in the
    > future benefit.

    > Stu

    It seems to me you’ve found one article that you want to believe over all
    the other articles available, as well as the advice from learned
    technicians, based on their education and experience. Many of these techs
    I’ve read in this thread are either experts in the field of brakes or are
    Master Diagnostic Technicians, which would lead one to believe the majority
    opinion of these is true.
    Are you possibly overanalyzing your situation?
    davidj92

  15. admin says:

    "Stuart A. Bronstein" wrote:
    > I’m realizing neither machining the rotors nor simply replacing them will
    > solve the problem, long term.

    What do you mean by "long term". As far as I can tell you are resisting
    the idea of fixing your brakes because eventually they will require
    fixing again. If you are hard on the brakes you can expect to have to
    repair them quite often. If you put your mind to it you can easily wear
    your brakes out in days.
            Nevertheless, if you develop a pulsation in the brakes and you replace
    the pads and rotors you can reasonably expect that to fix the problem
    and it should last as long as the originals did if you drive the same as
    before. Anybody who knows what they are doing will also make sure the
    calipers and pistons are clean, that they move freely and are generally
    in good working order and if not they should be fixed also.
            In most cases buying replacement rotors costs the same or very little
    more than having the rotors turned so just buy the rotors and you won’t
    have to worry about the rotors not being turned properly. That should
    address most of the worries from the article you are so fond of.

    -jim

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  16. admin says:

    "davidj92" <davidj92REM…@sigecom.net> wrote in
    news:l9GdndF_XfPAvpbZRVn-gw@sigecom.net:

    > It seems to me you’ve found one article that you want to believe over
    > all the other articles available … [you should] believe the majority
    > opinion … is true.

    Hi David,

    Actually I found many articles, some with conflicting ideas.

    For example, some say we should replace with softer brake pads, others
    say we should always true brand new rotors, other say never true rotors
    off the vehicle, others say use the parking brake instead of the pedal
    when stopped at a light due to cooling differences, etc.

    The majority is often wrong, by the way. The majority will tell you, in
    and of itself, that high octane gas is "better" gas just like the
    majority of chiropracters will tell you your spine needs "adjustment".

    There is only one truth, and I’m simply searching for that one truth.

    Here’s a quick summary to date of some of those articles
    Stu

    What causes high-speed brake induced shimmy?

    Vibration felt in the steering wheel only when the brakes are
    applied is not a front end alignment problem, but a brake problem.
    http://www.trustmymechanic.com/besttires.html

    The steering wheel is vibrating because the front brake
    rotors are warped (we call this vibration "shimmy").
    http://www.trustmymechanic.com/brakewarp.html

    Cold judder occurs primarily as a result of a non-uniform
    circumferential rotor (friction ring) thickness, which causes a
    cyclic variation in the brake torque output during braking (1 –
    2). These microscopic variations in the cross-sectional thickness
    of the disc brake rotor, axiomatically referred to as Disc Thickness
    Variations (D.T.V. or R.T.V. (Rotor Thickness Variation)) may arise
    during rotor manufacture as a product of the machining process
    (typical manufactured D.T.V. < 7 m), or, as laboratory and field
    trial testing have demonstrated, may be generated throughout their
    lifetime in-service.  
    http://www.eurac-group.com/technote4.htm

    Warping can be caused by excessive heat build up, which softens the
    metal …  however with most ventilated discs … the sensation of
    warped brakes (wheel shimmy under braking) most often is a matter of
    a brake pad material operating outside of its designed temperature
    range and it has left a thick(er) than normal deposit in one area
    of the disc surface, creating a "sticky" spot that will grab every
    revolution of the disk.  In cars with automatic transmissions the
    driver applies brakes when the car is stopped … the brake pads
    remain in contact with the disc and the discs will cool unevenly
    … leading to warping.  
    http://en.wikipedia.org/wiki/Disk_brake

    Wheel shimmy during braking is often caused by thickness variation
    of the rotor disc. If the rotor has runout, a thin spot will develop
    by the continuous touch touch touch as the rotor turns while the
    brakes are not applied. When this thickness variation increases to
    approximately 0.007 inch, the pulsation can be felt by the driver.
    http://en.wikipedia.org/wiki/Disk_brake

    The accepted cause of brake-induced vibrations is disc thickness
    variation.  Disc thickness variation generated by off-brake running,
    uneven transfer of lining material to the disc surface, disc
    corrosion, and distortion of the disc under thermal loading. The
    variations in rotor disc thickness cause the brake fluid pressure
    in the caliper to fluctuate, resulting in torque variations.
    http://support.mscsoftware.com/cgi-bin/kb_files/Ford_Brake_Roughness_
    2001_NAUC.pdf

    Pre-loaded wheel bearings have no end play to "absorb" hub and rotor
    run-out.  Hence, almost 100% of any axial run-out of the hub and
    brake rotor are transmitted to the brake pads. This axial run-out or
    wobble in the rotor causes the brake pads to wear the rotor unevenly
    over time, producing two sections of the rotor, 180 degrees apart,
    where the rotor thickness becomes thinner than the other two sections.
    This difference in thickness is called Disk Thickness Variation or DTV.
    http://www.rtitech.com/latheinfo.htm

    In general, any run-out greater than 0.002" (50 microns) will
    lead to an increase in DTV of about 0.0004" (10 microns) in about
    3000-5000 miles. In most cars, when DTV reaches 0.0004" (10 microns)
    or only 4 ten-thousandths of an inch, the driver will complain of
    pedal pulsation, steering wheel shimmy, or brake shudder. The most
    important fact to consider here is that the installation of the
    wheel will almost always increase hub/rotor run-out by 0.001-0.0015"
    (25-40 microns), even if the lug nuts are carefully torqued.
    http://www.rtitech.com/latheinfo.htm

  17. admin says:

    jim <"sjedgingN0sp"@m…@mwt.net> wrote in
    news:1141580792_2413@sp6iad.superfeed.net:

    > What do you mean by "long term". …
    > Anybody who knows what they are doing will also make sure
    > the calipers and pistons are clean, that they move freely and are
    > generally in good working order and if not they should be fixed also.
    > In most cases buying replacement rotors costs the same or very
    > little more than having the rotors turned so just buy the rotors

    Hi Jim,

    You are the words of wisdom.
    – I will replace the rotors (I already ordered them from the best Toyota
    Internet dealership in the USA according to these newsgroups).
    – I will replace the pads and hardware too (already ordered them too).
    – I agree it is important to check that the four pistons in each caliper
    are moving freely as the disc thickness variation (DTV) is what caused the
    runout in the first place (not heating & cooling warpage).

    I’m not just interested in fixing my brakes (otherwise I’d just take them
    to any mechanic on the block). I’m interested in learning why it happened
    and how to prevent it from happening in the future.  And how to diagnose
    the problem properly.

    For example, if I follow your (correct) advice to check caliper and piston
    movement, it begs the question (which is NOT in the shop manuals)!

    How does one check that the front 2 calipers & 8 pistons move freely?

    Stu

  18. admin says:

    On many vehicles, such as my ’94 Jeep Grand Cherokee, it is important to
    torque the front wheel lugs to a specified point, on my Jeep it is 90
    foot/pounds.  If this isn’t done, my rotors warp in a very short time…

    "Stuart A. Bronstein" <spamt…@lexregia.com> wrote in message
    news:m_FOf.56512$dW3.24778@newssvr21.news.prodigy.com…

    - Hide quoted text — Show quoted text -

    > "davidj92" <davidj92REM…@sigecom.net> wrote in
    > news:l9GdndF_XfPAvpbZRVn-gw@sigecom.net:

    >> It seems to me you’ve found one article that you want to believe over
    >> all the other articles available … [you should] believe the majority
    >> opinion … is true.

    > Hi David,

    > Actually I found many articles, some with conflicting ideas.

    > For example, some say we should replace with softer brake pads, others
    > say we should always true brand new rotors, other say never true rotors
    > off the vehicle, others say use the parking brake instead of the pedal
    > when stopped at a light due to cooling differences, etc.

    > The majority is often wrong, by the way. The majority will tell you, in
    > and of itself, that high octane gas is "better" gas just like the
    > majority of chiropracters will tell you your spine needs "adjustment".

    > There is only one truth, and I’m simply searching for that one truth.

    > Here’s a quick summary to date of some of those articles
    > Stu

    > What causes high-speed brake induced shimmy?

    > Vibration felt in the steering wheel only when the brakes are
    > applied is not a front end alignment problem, but a brake problem.
    > http://www.trustmymechanic.com/besttires.html

    > The steering wheel is vibrating because the front brake
    > rotors are warped (we call this vibration "shimmy").
    > http://www.trustmymechanic.com/brakewarp.html

    > Cold judder occurs primarily as a result of a non-uniform
    > circumferential rotor (friction ring) thickness, which causes a
    > cyclic variation in the brake torque output during braking (1 –
    > 2). These microscopic variations in the cross-sectional thickness
    > of the disc brake rotor, axiomatically referred to as Disc Thickness
    > Variations (D.T.V. or R.T.V. (Rotor Thickness Variation)) may arise
    > during rotor manufacture as a product of the machining process
    > (typical manufactured D.T.V. < 7 m), or, as laboratory and field
    > trial testing have demonstrated, may be generated throughout their
    > lifetime in-service.
    > http://www.eurac-group.com/technote4.htm

    > Warping can be caused by excessive heat build up, which softens the
    > metal …  however with most ventilated discs … the sensation of
    > warped brakes (wheel shimmy under braking) most often is a matter of
    > a brake pad material operating outside of its designed temperature
    > range and it has left a thick(er) than normal deposit in one area
    > of the disc surface, creating a "sticky" spot that will grab every
    > revolution of the disk.  In cars with automatic transmissions the
    > driver applies brakes when the car is stopped … the brake pads
    > remain in contact with the disc and the discs will cool unevenly
    > … leading to warping.
    > http://en.wikipedia.org/wiki/Disk_brake

    > Wheel shimmy during braking is often caused by thickness variation
    > of the rotor disc. If the rotor has runout, a thin spot will develop
    > by the continuous touch touch touch as the rotor turns while the
    > brakes are not applied. When this thickness variation increases to
    > approximately 0.007 inch, the pulsation can be felt by the driver.
    > http://en.wikipedia.org/wiki/Disk_brake

    > The accepted cause of brake-induced vibrations is disc thickness
    > variation.  Disc thickness variation generated by off-brake running,
    > uneven transfer of lining material to the disc surface, disc
    > corrosion, and distortion of the disc under thermal loading. The
    > variations in rotor disc thickness cause the brake fluid pressure
    > in the caliper to fluctuate, resulting in torque variations.
    > http://support.mscsoftware.com/cgi-bin/kb_files/Ford_Brake_Roughness_
    > 2001_NAUC.pdf

    > Pre-loaded wheel bearings have no end play to "absorb" hub and rotor
    > run-out.  Hence, almost 100% of any axial run-out of the hub and
    > brake rotor are transmitted to the brake pads. This axial run-out or
    > wobble in the rotor causes the brake pads to wear the rotor unevenly
    > over time, producing two sections of the rotor, 180 degrees apart,
    > where the rotor thickness becomes thinner than the other two sections.
    > This difference in thickness is called Disk Thickness Variation or DTV.
    > http://www.rtitech.com/latheinfo.htm

    > In general, any run-out greater than 0.002" (50 microns) will
    > lead to an increase in DTV of about 0.0004" (10 microns) in about
    > 3000-5000 miles. In most cars, when DTV reaches 0.0004" (10 microns)
    > or only 4 ten-thousandths of an inch, the driver will complain of
    > pedal pulsation, steering wheel shimmy, or brake shudder. The most
    > important fact to consider here is that the installation of the
    > wheel will almost always increase hub/rotor run-out by 0.001-0.0015"
    > (25-40 microns), even if the lug nuts are carefully torqued.
    > http://www.rtitech.com/latheinfo.htm

  19. admin says:

    On Sun, 05 Mar 2006 18:21:06 GMT, "Stuart A. Bronstein"

    - Hide quoted text — Show quoted text -

    <spamt…@lexregia.com> wrote:
    >"davidj92" <davidj92REM…@sigecom.net> wrote in
    >news:l9GdndF_XfPAvpbZRVn-gw@sigecom.net:

    >> It seems to me you’ve found one article that you want to believe over
    >> all the other articles available … [you should] believe the majority
    >> opinion … is true.

    >Hi David,

    >Actually I found many articles, some with conflicting ideas.

    >For example, some say we should replace with softer brake pads, others
    >say we should always true brand new rotors, other say never true rotors
    >off the vehicle, others say use the parking brake instead of the pedal
    >when stopped at a light due to cooling differences, etc.

    >The majority is often wrong, by the way. The majority will tell you, in
    >and of itself, that high octane gas is "better" gas just like the
    >majority of chiropracters will tell you your spine needs "adjustment".

    >There is only one truth, and I’m simply searching for that one truth.

    >Here’s a quick summary to date of some of those articles
    >Stu

    >What causes high-speed brake induced shimmy?

    Generally the last 3 articles pretty well nail it, while many of the
    others contain truth.

    Rotor quality is one BIG variable – and todays rotors are not "aged"
    before finishing. The "green" castings relieve after machining – so
    often arive out of true from the factory.
    Warpage, in itself, seldom causes pedal pulsation OR steering shimmy
    unless it is quite sizeable. Thickness variation causes problems even
    if very close in tolerance.
    Vented rotors often have "callapse" problems, where several "fins"
    move in tolerance as the rotor ages, or in use.
    Particularly in the "salt belt" todays pads often cause a "glaze" on
    the rotors, which traps moisture and pits the rotor away. When it
    pits, the oxide layer expands behind the glaze, clausing "blisters"
    that cause pulsations.

    Machining the rotor temporarily solves the problem, but reduced
    thickness and mass makes warpage more likely.

    As for surfacing new rotors, SOME need surfacing. On Car machining
    will usually give you a truer disk – but since runout is NOT the big
    problem, off-car machining on a good lathe will sometimes give better
    parallellism than on-car machining, where vibrations can have an
    effect.
    Pad composition is one thing you CAN change to prevent or greatly
    reduce break pulsation problems. Anything with an iron metallic is
    going to cause problems in salt-belt areas. Brass metallic is MUCH
    better, from early Toyota experience, and carbon metallic or ceramic
    pads have proven to be a great improvement in my experience with later
    model Ford and GM vehicles.

    Carbon Metallic pads on my 90 Aerostar improved rotor life by over
    400%, and pad life by 100% over factory parts. Brake effectiveness was
    also GREATLY improved – allowing me to actually lock the front wheels
    on dry pavement, which was absolutely impossible with the factory
    pads.

    - Hide quoted text — Show quoted text -

    >Vibration felt in the steering wheel only when the brakes are
    >applied is not a front end alignment problem, but a brake problem.
    >http://www.trustmymechanic.com/besttires.html

    >The steering wheel is vibrating because the front brake
    >rotors are warped (we call this vibration "shimmy").
    >http://www.trustmymechanic.com/brakewarp.html

    >Cold judder occurs primarily as a result of a non-uniform
    >circumferential rotor (friction ring) thickness, which causes a
    >cyclic variation in the brake torque output during braking (1 –
    >2). These microscopic variations in the cross-sectional thickness
    >of the disc brake rotor, axiomatically referred to as Disc Thickness
    >Variations (D.T.V. or R.T.V. (Rotor Thickness Variation)) may arise
    >during rotor manufacture as a product of the machining process
    >(typical manufactured D.T.V. < 7 m), or, as laboratory and field
    >trial testing have demonstrated, may be generated throughout their
    >lifetime in-service.  
    >http://www.eurac-group.com/technote4.htm

    >Warping can be caused by excessive heat build up, which softens the
    >metal …  however with most ventilated discs … the sensation of
    >warped brakes (wheel shimmy under braking) most often is a matter of
    >a brake pad material operating outside of its designed temperature
    >range and it has left a thick(er) than normal deposit in one area
    >of the disc surface, creating a "sticky" spot that will grab every
    >revolution of the disk.  In cars with automatic transmissions the
    >driver applies brakes when the car is stopped … the brake pads
    >remain in contact with the disc and the discs will cool unevenly
    >… leading to warping.  
    >http://en.wikipedia.org/wiki/Disk_brake

    >Wheel shimmy during braking is often caused by thickness variation
    >of the rotor disc. If the rotor has runout, a thin spot will develop
    >by the continuous touch touch touch as the rotor turns while the
    >brakes are not applied. When this thickness variation increases to
    >approximately 0.007 inch, the pulsation can be felt by the driver.
    >http://en.wikipedia.org/wiki/Disk_brake

    >The accepted cause of brake-induced vibrations is disc thickness
    >variation.  Disc thickness variation generated by off-brake running,
    >uneven transfer of lining material to the disc surface, disc
    >corrosion, and distortion of the disc under thermal loading. The
    >variations in rotor disc thickness cause the brake fluid pressure
    >in the caliper to fluctuate, resulting in torque variations.
    >http://support.mscsoftware.com/cgi-bin/kb_files/Ford_Brake_Roughness_
    >2001_NAUC.pdf

    >Pre-loaded wheel bearings have no end play to "absorb" hub and rotor
    >run-out.  Hence, almost 100% of any axial run-out of the hub and
    >brake rotor are transmitted to the brake pads. This axial run-out or
    >wobble in the rotor causes the brake pads to wear the rotor unevenly
    >over time, producing two sections of the rotor, 180 degrees apart,
    >where the rotor thickness becomes thinner than the other two sections.
    >This difference in thickness is called Disk Thickness Variation or DTV.
    >http://www.rtitech.com/latheinfo.htm

    >In general, any run-out greater than 0.002" (50 microns) will
    >lead to an increase in DTV of about 0.0004" (10 microns) in about
    >3000-5000 miles. In most cars, when DTV reaches 0.0004" (10 microns)
    >or only 4 ten-thousandths of an inch, the driver will complain of
    >pedal pulsation, steering wheel shimmy, or brake shudder. The most
    >important fact to consider here is that the installation of the
    >wheel will almost always increase hub/rotor run-out by 0.001-0.0015"
    >(25-40 microns), even if the lug nuts are carefully torqued.
    >http://www.rtitech.com/latheinfo.htm

    *** Free account sponsored by SecureIX.com ***
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  20. admin says:

    - Hide quoted text — Show quoted text -

    "Stuart A. Bronstein" wrote:

    > jim <"sjedgingN0sp"@m…@mwt.net> wrote in
    > news:1141580792_2413@sp6iad.superfeed.net:
    > > What do you mean by "long term". …
    > > Anybody who knows what they are doing will also make sure
    > > the calipers and pistons are clean, that they move freely and are
    > > generally in good working order and if not they should be fixed also.
    > > In most cases buying replacement rotors costs the same or very
    > > little more than having the rotors turned so just buy the rotors

    > Hi Jim,

    > You are the words of wisdom.
    > – I will replace the rotors (I already ordered them from the best Toyota
    > Internet dealership in the USA according to these newsgroups).
    > – I will replace the pads and hardware too (already ordered them too).
    > – I agree it is important to check that the four pistons in each caliper
    > are moving freely as the disc thickness variation (DTV) is what caused the
    > runout in the first place (not heating & cooling warpage).

    Well, I’m not sure I trust your analysis. It is quite likely that in one
    way or another heat was a major factor that led to the problem
    developing.  That  put another way, if you drive so that the brakes
    never get hot it’s likely they will last a very long time. All the
    energy in a car moving at 70 mph goes into the brakes when you make a
    sudden stop. You don’t want to put your hand on the discs after doing
    that. And if your rotors are truly not the same thickness that didn’t
    happen all at once – it happened over time and quite a number of things
    could have started the process most all of them related to heat,
    followed by rust, salt and dirt.
             I assume you feel that your brakes needed replacement sooner than they
    should have. That points to the driver as the most likely cause. Some
    drivers regularly have to replace brakes every 10000 miles others can
    get 100000 miles (altho that may be hard to do where salt plays a big
    role in the deterioration of brakes). Also, some cars tend to have
    brakes that last longer and take more abuse than others.

    > I’m not just interested in fixing my brakes (otherwise I’d just take them
    > to any mechanic on the block). I’m interested in learning why it happened
    > and how to prevent it from happening in the future.  And how to diagnose
    > the problem properly.

    > For example, if I follow your (correct) advice to check caliper and piston
    > movement, it begs the question (which is NOT in the shop manuals)!

    > How does one check that the front 2 calipers & 8 pistons move freely?

    In order to change the brake pads and rotors you need to move the
    calipers and pistons to their wide open position of there travel. You
    should be able to tell if they are able to move normally. Rust of course
    is what usually causes sticking problems. Disc brake pistons don’t have
    much clearance so it doesn’t take much to jam them up.

    —-== Posted via Newsfeeds.Com – Unlimited-Unrestricted-Secure Usenet News==—-
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  21. admin says:

    "jim" <"sjedgingN0sp"@m…@mwt.net> wrote in message

    news:1141434475_67@sp6iad.superfeed.net…

    > hob wrote:

    > > > Even a first year engineering student can tell you how hard  braking
    with
    > > > the linkage turned hard over bends (warps) the rotor bell.

    > That’s just plain silly.

    It is only silly to those without brake engineering experience who assume
    transverse forces into the rotor disc are negligible, or who attend pretty
    weak schools.

       I have designed and built several of the machines that test wheels,
    tires, and linkages on motor vehicles for Ford and GM, and I can assure you
    that there are forces imparted transversely to the rotor disc when the
    linkage is not straight ahead and the brakes are applied.
      Hi-speed photos of wheels heeling in hard braking turns show that that
    cute little axle shaft holding on the wheel is aided in resisting total
    failure by the caliper-and-disk.  Looking at an accident where the wheel is
    turned off the vehicle centerline axis at impact clearly shows the disk
    assembly damage.

      The rotor bell on a jeep wrangler is an excellent example for
    illustration.  Its linkage allows a greater angle off the vehicle axis than
    on-road passenger vehicles, and the rotor is mounted off the axis of the
    rotor disc. The mounting flange connecting the bell to the axle is
    relatively thin material that is expected to deflect enough so as not to
    reach the proportional limit.
      Notice the size of the hold-down bolts and key-slider of the caliper
    relative to the size of the axle and consider the moments imparted into the
    axle-caliper-pin-rotor disk loop.
       When the caliper is turned sideways to the direction of vehicle travel
    and engaged, the momentum and resultant forces are no longer in the plane of
    the rotor disk face, but rather across, and they become moments across the
    bolts and keys, reacted into the face of the rotor (and across the face of
    the disc itself) and the axle.
       Hard turns and heavy braking will definitely warp that disk out of plane

    The manifestation of transverse load is more pronounced in offset rotor
    discs and with off-road where the greater limits lock to lock allow greater.

    - Hide quoted text — Show quoted text -

    > > >   (imagine 2 tons moving forward trying to go over a tire turned
    sideways
    > > > with the brake pads locked onto the rotor, a rotor designed for
    transfer
    > > of
    > > > force into floating claipers and transversely into the axle.

    > The caliper can move freely from side to side (floating calipers). There
    > is no side load at all due to steering.

    > > >   Guess how the force gets from the 2 ton moving vehicle mass into the
    > > tire
    > > > tread in a turn– through the shoes gripping the rotor and back into
    the
    > > > axle – forces across the rotor plane, unlike straight ahead braking,
    where
    > > > the forces are in the rotor plane)

    > This is fantasy. The wheel is mounted solid to the axle with the rotor
    > sandwiched between.

    You apparently are not familiar with force analysis.  Any material receiving
    a force deflects, the amount of deflection depending on the geometry, the
    input force, and the material.
       There is no such thing as "solid" in engineering, there is only relative
    deflection.

       The wheel is is mounted to the axle through a flexible bolt pattern and
    the axle is a small diameter shaft that does deflect.  A lot less straight
    ahead than when turning.
        It particularly deflects when the moment it sees is increased from the
    weight and braking dynamic force acting in a plane parallel to the vehicle
    axis an inch from the axle shaft mount arm in straight-ahead braking;
       increased due to
       1) the increased moment due to the wheel turned across the direction of
    travel which causes the moment from the tread gripping the road to no longer
    be "next to " the mounting plane in the plane of the wheel, but rather
    across the plane of the disc:  twenty times as great because of the
    tread-to-mount distance of a transversely directed
    (turned-to-plane-of-travel) force at the tread compared to the tread-to
    mount-distance of an axially directed (straight-ahead-travel)force.
    and
      2) a greater dynamic braking input (greater from the leading turned wheel
    getting more of the vehicle-braking dynamic forces from the resultant
    moment, similar to the front wheels having more force than the rear in a
    straight-shead stop)

    Even if the axle would deflect it couldn’t possibly

    > deflect enough to exceed the side travel of the calipers. If the car is
    > sliding sideways the brakes see no load at all because there would be no
    > force to turn the wheels.
    > Heat build up is usually what causes rotors to warp.

    Materials science one – heating steel does not warp steel- it removes
    residual stresses of manufacture – annealing, etc. -and makes a more stable
    part.

      However, it is easier to bend a heated piece of metal than a cool one –
    and any forces across the plane of the heated disc are more prone to
    deforming the disc.

     If you wish to warp a rotor, put in the force when the rotor is heated.
    Heating a rotor will only warp it if it has residual stresses from
    manufacturing that were not removed before truing.

    You don’t even

    > have to put the rotor on a car just toss it in a fire and it will warp.

     Not if you keep the face-plane vertical.

    > Rust in the ventilation passages can also warp rotors. And frozen
    > calipers can also warp rotors – not so much because of uneven force
    > loads but uneven heat loads.

    Not because of uneven heat loads per se, but because the calipers wear the
    disc face unevenly.
      A rotor that has frozen calipers will heat a "high spot" on one side of
    the disc, and that high spot is easier to abrade when hot, so indirectly the
    heat allowing more wear can contribute – but it is not the heat itself.

    - Hide quoted text — Show quoted text -

    > > >  Any experienced engineer will tell you that if there is a problem and
    it
    > > > goes way when you replace a part, the problem is gone.
    > > >   Was the problem the root cause and will it return? Well, if it
    wasn’t
    > > part
    > > > of the problem, the problem would still be there in some form.
    > > >    However, if it is only part of the problem, the problem will later
    > > > manifest the same symptoms (E.g, if the driver brakes hard in corners,
    > > part
    > > > of the problem, the rotors will again bend/wear the faces so that in
    time
    > > > the plane of the rotor surfaces are no longer within tolerance, Before
    the
    > > > driver got in and warped the new rotors, the new rotors were just
    fine)

    > This is nonsense. Excessive braking can result in warped rotors, but
    > braking on turns has nothing to do with it.

    See above.  And hard braking during turns is the main cause of passenger
    vehicle rotor damage.

    - Hide quoted text — Show quoted text -

    > -jim

    > > >  ( Logically, when you change the rotor and then the problem goes
    away,
    > > the
    > > > problem is gone.)

    > > > and it seems
    > > > > nobody on this planet can really (reliably) tell the difference
    between
    > > > > brake friction materials (because there are no standards whatsoever)
    > > > > according to
    > > > > http://www.performanceoiltechnology.com/brakingsystems.htm

    > > > the man ought to read the specs in the vehicle manuals, which do
    indeed
    > > list
    > > > tolerances for rotors. And he ought to get some in depth background
    first.
    > > >    The internet is full of half-aware self-promoters with partially
    > > applied
    > > > theories.    And AMSOIL, no less.

    > > > FWIW –  match mounting is a way to limit costly close tolerance
    machining
    > > in
    > > > many mating parts- you make hundreds of parts all alike, and then
    measure
    > > > them – some will be way off and get tossed, most will be within
    tolerance
    > > > and used according to their tolerance, and some may even be perfect.
    It’s
    > > > cheaper than making each one perfect.

    > > > I’ll put this quote from them in here for the experienced engineers to
    get
    > > a
    > > > chcukle

    > > > "DTV is when the rotor thickness is not the same all the way around
    the
    > > > rotor. DTV is typically caused by lateral runout.  DTV can only be
    > > measured
    > > > with very specialized laboratory testing equipment or with special on
    > > > vehicle capacitance probes."

    > > > right…. ( or like a shop caliper or shop "mic", as noted in the
    > > > maintenance manuals.)

    > > >  Quote – "This [DTV] phenomenon is what many technicians refer to as
    > > > "warping", however they actually think the rotor warped and needs
    > > > replacement."

    > > >  OK, so what they are saying is that the rotor isn’t warped ( and so
    the
    > > > rotor is true?) and the face of the rotor plane has just warped, and
    so
    > > they
    > > > are saying that
    > > >    instead of the rotor needing replacing because the thickness
    varies,
    > > the
    > > > rotor needs replacing because the thickness varies and the esoteric
    DTV
    > > > measurements are lab things .(or you could just get refacing done at a
    > > brake
    > > > shop, if enough material is left).

    > > > enough of quoting their home-spun humor….

    > > > > So, since I have horrible brake-induced wobble in my Toyota 4Runner,
    how
    > > > > DOES anyone  buy the right parts given there are no regulations or
    > > > > standards to protect us?

    > > > There are regulations – Check out the following standards for brake
    > > > materials:  DE3A, BEEP,  NHTSA FMVSS-105

    > > > > We may as well close our eyes and choose randomly for all the lack
    of
    > > > > standards. Which leaves me to my most important question, having to
    > > trust
    > > > > in your judgement and experience (which I don’t have).

    > > > > Where would YOU buy a good quality rotors & pads for a Toyota
    4Runner?

    > > > From Toyota –
    > > >   why?  aftermarket pads have few, if any standards.  New-car brake
    pads
    > > > (OEM) have to meet NHTSA standards, and thus actually do stop better,
    are
    > > > more reliable, and the dust around the kids and dogs is less
    hazardous.

    > > > nuff free stuff

    > > > > Stu

    > —-== Posted via Newsfeeds.Com –

    read more »

  22. admin says:

    - Hide quoted text — Show quoted text -

    hob wrote:

    > "jim" <"sjedgingN0sp"@m…@mwt.net> wrote in message
    > news:1141434475_67@sp6iad.superfeed.net…

    > > hob wrote:

    > > > > Even a first year engineering student can tell you how hard  braking
    > with
    > > > > the linkage turned hard over bends (warps) the rotor bell.

    > > That’s just plain silly.

    > It is only silly to those without brake engineering experience who assume
    > transverse forces into the rotor disc are negligible, or who attend pretty
    > weak schools.

    >    I have designed and built several of the machines that test wheels,
    > tires, and linkages on motor vehicles for Ford and GM, and I can assure you
    > that there are forces imparted transversely to the rotor disc when the
    > linkage is not straight ahead and the brakes are applied.

    Frankly I doubt your credentials. But in the event that you are who you
    claim you clearly have not grasp the subject of this thread. No one is
    interested in what happens to the rotors when there is a catastrophic
    axle failure.

    >   Hi-speed photos of wheels heeling in hard braking turns show that that
    > cute little axle shaft holding on the wheel is aided in resisting total
    > failure by the caliper-and-disk.  Looking at an accident where the wheel is
    > turned off the vehicle centerline axis at impact clearly shows the disk
    > assembly damage.

    Well yes, if the axle gets bent that much so that the calipers are force
    to the end of their travel then the rotors absorb the load. But so what.
    That’s hardly got anything to do with someone who needs a brake job. You
    are talking about someone who has totaled their car.

            `I agree if the side load is enough to deflect the axle so that the
    brake assembly is caused to slide to the end of its travel then there is
    definitely a load on the calipers and rotors. But until the axle
    deflects that much there will be very little load on the disk because
    the calipers are designed to slide sideways. And if your axle does
    deflect that much you have a lot more serious problems than just a
    rotor. But for normal drivers under normal driving conditions this
    doesn’t play any role in why rotors don’t run true and develop uneven
    wear patterns which is the subject of the thread.

    -jim

    - Hide quoted text — Show quoted text -

    >   The rotor bell on a jeep wrangler is an excellent example for
    > illustration.  Its linkage allows a greater angle off the vehicle axis than
    > on-road passenger vehicles, and the rotor is mounted off the axis of the
    > rotor disc. The mounting flange connecting the bell to the axle is
    > relatively thin material that is expected to deflect enough so as not to
    > reach the proportional limit.
    >   Notice the size of the hold-down bolts and key-slider of the caliper
    > relative to the size of the axle and consider the moments imparted into the
    > axle-caliper-pin-rotor disk loop.
    >    When the caliper is turned sideways to the direction of vehicle travel
    > and engaged, the momentum and resultant forces are no longer in the plane of
    > the rotor disk face, but rather across, and they become moments across the
    > bolts and keys, reacted into the face of the rotor (and across the face of
    > the disc itself) and the axle.
    >    Hard turns and heavy braking will definitely warp that disk out of plane

    > The manifestation of transverse load is more pronounced in offset rotor
    > discs and with off-road where the greater limits lock to lock allow greater.

    > > > >   (imagine 2 tons moving forward trying to go over a tire turned
    > sideways
    > > > > with the brake pads locked onto the rotor, a rotor designed for
    > transfer
    > > > of
    > > > > force into floating claipers and transversely into the axle.

    > > The caliper can move freely from side to side (floating calipers). There
    > > is no side load at all due to steering.

    > > > >   Guess how the force gets from the 2 ton moving vehicle mass into the
    > > > tire
    > > > > tread in a turn– through the shoes gripping the rotor and back into
    > the
    > > > > axle – forces across the rotor plane, unlike straight ahead braking,
    > where
    > > > > the forces are in the rotor plane)

    > > This is fantasy. The wheel is mounted solid to the axle with the rotor
    > > sandwiched between.

    > You apparently are not familiar with force analysis.  Any material receiving
    > a force deflects, the amount of deflection depending on the geometry, the
    > input force, and the material.
    >    There is no such thing as "solid" in engineering, there is only relative
    > deflection.

    >    The wheel is is mounted to the axle through a flexible bolt pattern and
    > the axle is a small diameter shaft that does deflect.  A lot less straight
    > ahead than when turning.
    >     It particularly deflects when the moment it sees is increased from the
    > weight and braking dynamic force acting in a plane parallel to the vehicle
    > axis an inch from the axle shaft mount arm in straight-ahead braking;
    >    increased due to
    >    1) the increased moment due to the wheel turned across the direction of
    > travel which causes the moment from the tread gripping the road to no longer
    > be "next to " the mounting plane in the plane of the wheel, but rather
    > across the plane of the disc:  twenty times as great because of the
    > tread-to-mount distance of a transversely directed
    > (turned-to-plane-of-travel) force at the tread compared to the tread-to
    > mount-distance of an axially directed (straight-ahead-travel)force.
    > and
    >   2) a greater dynamic braking input (greater from the leading turned wheel
    > getting more of the vehicle-braking dynamic forces from the resultant
    > moment, similar to the front wheels having more force than the rear in a
    > straight-shead stop)

    > Even if the axle would deflect it couldn’t possibly
    > > deflect enough to exceed the side travel of the calipers. If the car is
    > > sliding sideways the brakes see no load at all because there would be no
    > > force to turn the wheels.

    > > Heat build up is usually what causes rotors to warp.

    > Materials science one – heating steel does not warp steel- it removes
    > residual stresses of manufacture – annealing, etc. -and makes a more stable
    > part.

    >   However, it is easier to bend a heated piece of metal than a cool one –
    > and any forces across the plane of the heated disc are more prone to
    > deforming the disc.

    >  If you wish to warp a rotor, put in the force when the rotor is heated.
    > Heating a rotor will only warp it if it has residual stresses from
    > manufacturing that were not removed before truing.

    > You don’t even
    > > have to put the rotor on a car just toss it in a fire and it will warp.

    >  Not if you keep the face-plane vertical.

    > > Rust in the ventilation passages can also warp rotors. And frozen
    > > calipers can also warp rotors – not so much because of uneven force
    > > loads but uneven heat loads.

    > Not because of uneven heat loads per se, but because the calipers wear the
    > disc face unevenly.
    >   A rotor that has frozen calipers will heat a "high spot" on one side of
    > the disc, and that high spot is easier to abrade when hot, so indirectly the
    > heat allowing more wear can contribute – but it is not the heat itself.

    > > > >  Any experienced engineer will tell you that if there is a problem and
    > it
    > > > > goes way when you replace a part, the problem is gone.
    > > > >   Was the problem the root cause and will it return? Well, if it
    > wasn’t
    > > > part
    > > > > of the problem, the problem would still be there in some form.
    > > > >    However, if it is only part of the problem, the problem will later
    > > > > manifest the same symptoms (E.g, if the driver brakes hard in corners,
    > > > part
    > > > > of the problem, the rotors will again bend/wear the faces so that in
    > time
    > > > > the plane of the rotor surfaces are no longer within tolerance, Before
    > the
    > > > > driver got in and warped the new rotors, the new rotors were just
    > fine)

    > > This is nonsense. Excessive braking can result in warped rotors, but
    > > braking on turns has nothing to do with it.

    > See above.  And hard braking during turns is the main cause of passenger
    > vehicle rotor damage.

    > > -jim

    > > > >  ( Logically, when you change the rotor and then the problem goes
    > away,
    > > > the
    > > > > problem is gone.)

    > > > > and it seems
    > > > > > nobody on this planet can really (reliably) tell the difference
    > between
    > > > > > brake friction materials (because there are no standards whatsoever)
    > > > > > according to
    > > > > > http://www.performanceoiltechnology.com/brakingsystems.htm

    > > > > the man ought to read the specs in the vehicle manuals, which do
    > indeed
    > > > list
    > > > > tolerances for rotors. And he ought to get some in depth background
    > first.
    > > > >    The internet is full of half-aware self-promoters with partially
    > > > applied
    > > > > theories.    And AMSOIL, no less.

    > > > > FWIW –  match mounting is a way to limit costly close tolerance
    > machining
    > > > in
    > > > > many mating parts- you make hundreds of parts all alike, and then
    > measure
    > > > > them – some will be way off and get tossed, most will be within
    > tolerance
    > > > > and used according to their tolerance, and some may even be perfect.
    > It’s
    > > > > cheaper than making each one perfect.

    > > > > I’ll put this quote from them in here for the experienced engineers to
    > get
    > > > a
    > > > > chcukle

    > > > > "DTV is when the rotor thickness is not the same all the way around
    > the
    > > > > rotor. DTV is typically caused by lateral runout.  DTV can only be
    > > > measured
    > > > > with very specialized laboratory testing equipment or with special on
    > > > > vehicle capacitance probes."

    > > > > right…. ( or like a shop caliper or shop "mic", as noted in the
    > > > > maintenance manuals.)

    > > > >  Quote – "This [DTV] phenomenon is what many technicians refer to as
    > > > > "warping", however they actually think the rotor warped and needs
    > > > > replacement."

    > > > >  OK, so what they are

    read more »

  23. admin says:

    "Emmo" <e…@austin.rr.com> wrote in news:ZDGOf.5257$gm.1937
    @tornado.texas.rr.com:

    > On my ’94 Jeep Grand Cherokee, it is important to torque
    > the front wheel lugs to 90 foot/pounds.  
    > If this isn’t done, my rotors warp in a very short time…

    Hi Emmo,
    I agree and disagree (now that I’ve done some research).
    I agree one should do a three pass tightening of the lug nuts, which, in
    the case of the six-lug-nut 1998 Toyota 4Runner, is 84 foot pounds.

    FIRST PASS: While the truck is in the air, tighten three lug nuts by hand
    in a triangle pattern; then tighten the other three in a reverse triangle
    pattern.

    SECOND PASS: Back on the ground, tighten the second lug nut triangle to 1/2
    the recommended torque (42 foot pounds for a 1998 Toyota 4Runner); then do
    the same for the first triangle set of lug nuts.

    THIRD PASS: Finally, tighten the first triangle to full torque; and then
    the second triangel to full torque.

    Of course, this assumes the hub was cleaned of all rust and was greased
    with synthetic Mobil 1 grease to prevent rust creep (pushing out of the
    rotors like tree roots push out a sidewalk or curb).

    However, now that I’ve learned enough to be dangerous, I will disagree with
    your assertion that the rotors will "warp" if you tighten lug nuts
    incorrectly. Many articles have shown that brake discs almost never warp.
    What people call warp is really disk thickness variation or rotor thickness
    variation caused by the pad deposition being different on various parts of
    the rotor.

    See a more detailed explanation in the following reference:
    http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml#

    Stu

  24. admin says:

    "Stuart A. Bronstein" <spamt…@lexregia.com> wrote in message
    news:A3LOf.18881$rL5.17151@newssvr27.news.prodigy.net…

    > However, now that I’ve learned enough to be dangerous, I will disagree
    > with
    > your assertion that the rotors will "warp" if you tighten lug nuts
    > incorrectly. Many articles have shown that brake discs almost never warp.
    > What people call warp is really disk thickness variation or rotor
    > thickness
    > variation caused by the pad deposition being different on various parts of
    > the rotor.

    Dear Stuart,
    I know for a fact, that incorrectly tightening lugnuts will
    warp rotors. (even brand new rotors).
    I can prove it on just about any vehicle.
    (not just hubless types)
    Those websites are just playing on words mostly and also
    must not know that even a 0 thickness variation can still have a
    warp in the rotor if the wheels are not properly tightened.
    You really should not listen to websites as if they are law..
    Since if you do.
    There are websites that have proof of many other things
    that are far more silly than the "rotors can not warp" bologna
    you are reading.


    James M Driscoll Jr
    Spaceman

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