Bad shimmy upon heavy braking Toyota 4Runner (why?)

"Stuart A. Bronstein" <spamtrap@lexregia.com> wrote in message
news:nYGOf.65943$PL5.29675@newssvr11.news.prodigy.com...[color=blue]
> Skip <skipfromla@yahoo.com> wrote in
> news:fc8e02t0e6o42bcah3rj1epfucei0ac3ef@4ax.com:
>[color=green]
>> My 2000 Tundra developed the same thing, starting at about 35,000
>> miles. I asked the Toyota dealer's service manager about it and was
>> told that some of the Tundras had brake systems that were too light
>> duty for the PU. He also told me there was a TSB on the problem[/color]
>
> I couldn't find that Toyota TSB for the 1998 4Runner but I did find that
> the main cause of brake shimmy is brake material buildup on the rotors.
>
> [url]http://www.zeckhausen.com/avoiding_brake_judder.htm[/url]
> says "Despite the popular myth, brake judder is not caused by warped
> rotors. Judder is the result of a thickness variation in pad buildup on
> the rotors' surfaces."[/color]

That site is talking about a problem when you change from
street brakepads to racing brakepads without changing the rotors.
If you are not doing such, it is simply not a cause for your problem.

Brake rotors DO warp.
The "warping" also known as "lateral runout", is caused mostly
by an incorrect tightening of lugnuts when a tire/wheel is changed.

It can also (rarely) be caused by overheating in areas where the rotor
has a problem with uneven cooling such as blocked vent holes in some rotor
styles.

[color=blue]
> So, I'm replacing the pads and rotors but that is not a long term
> solution.
> I need to find how to test and eliminate the four pistons from sticking in
> the caliper. Pads won't solve the problem. Since nobody can tell the
> quality of aftermarket pads (which was proven in the preceeding threads)
> I'm going OEM (it's the only way one can go and have any given truth)
> which
> means the brake shudder will likely re-occur at the 50,000 mile mark
> regularly unfortunately.[/color]

If a proper brakejob is done, and you ALWAYS tighten lugnuts correctly.
no problem will arise later except the fact you will need
to replace worn pads and "worn" rotors. (usually pads only if no excess
wear of the rotors has occured)
and..
Yes rotors also wear so later on you will need to replace them also.

These websites you are finding that state "a rotor can not warp" might as
well be saying "steel can not be bent".
In short,, those website experts... are bent.

--
James M Driscoll Jr
Spaceman

"Spaceman" <Realspace@comcast.not> wrote in
news:fZmdnULG7r9C3JbZRVn-pg@comcast.com:[color=blue]
> Brake rotors DO warp.
> The "warping" also known as "lateral runout", is caused mostly
> by an incorrect tightening of lugnuts when a tire/wheel is changed.
> It can also (rarely) be caused by overheating in areas where the rotor
> has a problem with uneven cooling such as blocked vent holes
> If a proper brakejob is done, and you ALWAYS tighten lugnuts
> correctly. no problem will arise later except the fact you will need
> to replace worn pads and "worn" rotors.
> Rotors also wear so later on you will need to replace them also.[/color]

Hi James,

I understand that rotors "can" wear out once they reach their wear limit.

However, it's interesting that everyone "says" the wear limit is for heat
dissipation but (according to the articles I've quoted), it's not. The wear
limit is imposed to reduce the risk of the pistons falling out. Amazing.
What I've thought for so many years is wrong.

In addition, I've also learned that while I could true the rotors, I should
(and will) replace the rotors and the pads with OEM rotors and pads, mainly
because there are absolutely no standards that aftermarket rotors and pads
have to meet yet which OEM braking systems must meet (FMVSS 105 and FMVSS
135 for example).

Furthermore, I've learned that I should go to one of the two best Internet
Toyota dealerships because they offer OEM parts at more than 25% less than
my three closest Toyota dealerships did (I checked a dozen suppliers and
found this to be true. In fact, one local dealership charged 5% MORE than
list! Obviously I'll never go to him for parts!).

However, even after all that research, I've learned that the brake judder
(aka brake shudder, shimmy, vibration, pedal pulsation, etc) problem WILL
RETURN if the real cause is the brake pistons sticking in their calipers.

So, if the root cause is really do to the brake pistons "sticking", then
I'll have the problem all over again in a few thousand miles! So, now I've
moved on to researching how to tell if a piston is sticking (see a separate
thread on that which concludes, so far, there is no instrument out there
that will provide measurable values for brake piston sticking).

The net is that if I just do as you said, then I could get the brake judder
again in just a few thousand miles. That's why I'm doing all this research!

Thanks for all your help for me and others,
Stu

"Stuart A. Bronstein" <spamtrap@lexregia.com> wrote in message
news:ROLOf.44917$H71.36076@newssvr13.news.prodigy.com...[color=blue]
> "Spaceman" <Realspace@comcast.not> wrote in
> news:fZmdnULG7r9C3JbZRVn-pg@comcast.com:[color=green]
>> Brake rotors DO warp.
>> The "warping" also known as "lateral runout", is caused mostly
>> by an incorrect tightening of lugnuts when a tire/wheel is changed.
>> It can also (rarely) be caused by overheating in areas where the rotor
>> has a problem with uneven cooling such as blocked vent holes
>> If a proper brakejob is done, and you ALWAYS tighten lugnuts
>> correctly. no problem will arise later except the fact you will need
>> to replace worn pads and "worn" rotors.
>> Rotors also wear so later on you will need to replace them also.[/color]
>
> Hi James,
>
> I understand that rotors "can" wear out once they reach their wear limit.
>
> However, it's interesting that everyone "says" the wear limit is for heat
> dissipation but (according to the articles I've quoted), it's not. The
> wear
> limit is imposed to reduce the risk of the pistons falling out. Amazing.
> What I've thought for so many years is wrong.[/color]

The limit is also for rotor failure by simple crushing.
rotors that are too thin can actually be crushed by the massive forces
a piston can impose on them in a "stomp" on the pedal with power
assistance helping it.

[color=blue]
> In addition, I've also learned that while I could true the rotors, I
> should
> (and will) replace the rotors and the pads with OEM rotors and pads,
> mainly
> because there are absolutely no standards that aftermarket rotors and pads
> have to meet yet which OEM braking systems must meet (FMVSS 105 and FMVSS
> 135 for example).[/color]

I agree that there are no standards.
But I do know I have never had any problems with a company
like Raybestos but the funny thing is sometimes the Dealership prices
are actually better than some "high quality" after market OEM pads.

[color=blue]
> However, even after all that research, I've learned that the brake judder
> (aka brake shudder, shimmy, vibration, pedal pulsation, etc) problem WILL
> RETURN if the real cause is the brake pistons sticking in their calipers.[/color]

Yes, that is true but it won't happen near as fast as an incorrectly
torqued wheel could do it.
:)

[color=blue]
> So, if the root cause is really do to the brake pistons "sticking", then
> I'll have the problem all over again in a few thousand miles! So, now I've
> moved on to researching how to tell if a piston is sticking (see a
> separate
> thread on that which concludes, so far, there is no instrument out there
> that will provide measurable values for brake piston sticking).[/color]

One way to tell if the pistons are sticking is with your old
pads and rotors.
with the vehicle properly supported and the wheel off
First, carefully pry the old brake pads back
(pushing the pistons back a bit) so you can see
space in between the pads and rotor.
then have someone simply press on the brake.
you should see both sides come in and touch the rotor.
(not always equally but should be very close to equal)
and repeat for the other side.

If you have a sliding type caliper, you simply need to
remove pads and rotors and make sure the caliper
slides nice side to side on the pins that allow it to do such.

[color=blue]
> The net is that if I just do as you said, then I could get the brake
> judder
> again in just a few thousand miles. That's why I'm doing all this
> research!
>
> Thanks for all your help for me and others,[/color]

No prob.
:)

After reading all of your posts on this I can say one big item. I hope
you never rebuild an engine.

Keep in mind that well over half of what you read online is WRONG. Why?
Real simple, anybody can put up a site and write whatever they want. As
far as the websites you quote as saying there are no standards about
brake parts they are flat out wrong, there are many different standards
for replacement parts and many are more strict than the factory ones
simply because of the liability factor involved.
I would trust folks who actually work on vehicles for a living over ANY
web site. Oh and consider also that factory manuals have been known to
have errors as well. The main reason why your factory manuals are the
way they are is simple as well. They are translations of manuals written
in Japanese, as such they are subject to errors when they are
translated.

The main cause of brake problems is NOT build up of brake material, the
main cause is HEAT with rust being a very close second.
The heat is generated every time you use those brakes, that is the way
they work to stop the vehicle, the pads press the rotors and the
friction slows/stops the vehicle. That friction generates heat. Heat ANY
metal object and allow it to cool, it will alter it dimensionally. Now
take a look at your brakes, notice anything? Clue: Note that although
the rotor is open to the air for the most part the area under the pads
is not. What this means is that after you apply the brakes and stop they
start to cool down, the problem is that the rotor will cool reasonably
uniform EXCEPT for the area under those pads where the airflow is
blocked. Now as you drive the brakes rotate, so the spot that gets heat
soaked changes every time. This should make the brake rotor change the
same around the entire rotor. It won't however because the rotor is
usually made from cast iron and they are machined and balanced from a
casting. The balancing can make some areas marginally thinner from the
start. That can be enough to cause warpage. Another area that WILL cause
warpage is using the brakes and hitting standing water, or even taking
the car through a car wash if you have been driving in heavy stop/go
driving. If you want to see heat warpage first hand take ANY metal pan
(don't use a very good one or your wife's favorite though) Set it on the
counter cold and see if it is close to flat. Now toss it on the stove
and heat it up using high heat. Once it is hot take it off the stove and
set it on a flat surface that can handle the heat. Notice that it has
moved dimensionally? If you really want to see it pour some cold water
in there when it is still hot. That is what happens to your brake rotors
if they get hit with water/snow after being used hard. The last heat
related item is warpage from the brake caliper itself. If it is binding
or if rust or crud is causing it to be in any position other than
parallel to the rotor vertically and horizontally it will attempt to
bend the rotor every time you apply the brakes. Panic stops will apply
some very high pressures to those rotors as well. Enough to bend them
enough to cause problems.

Rust on the other hand starts as soon as the coating of oil on the rotor
burns off. The pads also have an effect here as well. Say you have just
driven your car in stop and go traffic and used the brakes quite a bit
on the way to work. You pull into your space and notice it is a little
cool out. No problem for you BUT for the brakes that cool air starts to
flow around the brakes and as they cool moisture from the air causes
them to rust slightly. The pad area will be protected though and it will
still retain heat as well. Not good for the rotors. Now you drive home
at the end of the day and park. Over night the dew falls or it rains.
The increased moisture attacks the cast iron some more, and again the
pads protect the area they cover. This cycle happens every day. It can
get so bad that there will be pieces of rust actually burnished into the
rotor surface. Rust also can effect the pads themselves. Depending on
what they are made of it can cause them to corrode or if your in an
industrial area there may be some chemical in the are that can cause
problems with them.

Personally I would buy some rotors from NAPA or the dealer, performance
friction pads and new calipers. clean up the hubs with the glass beader.
Clean any oil/coating off the rotors. Install them. Use my double nose
brake gauge to check the runout. If OK I would R&R the calipers, install
them, then bleed the system with new fluid. Then pull the back brakes
apart and rebuild them as well. I would also check the tire balances and
rotate them.
--
Steve Williams

"Stuart A. Bronstein" <spamtrap@lexregia.com> wrote in message
news:nYGOf.65943$PL5.29675@newssvr11.news.prodigy.com...[color=blue]
> Skip <skipfromla@yahoo.com> wrote in
> news:fc8e02t0e6o42bcah3rj1epfucei0ac3ef@4ax.com:
>[color=green]
> > My 2000 Tundra developed the same thing, starting at about 35,000
> > miles. I asked the Toyota dealer's service manager about it and was
> > told that some of the Tundras had brake systems that were too light
> > duty for the PU. He also told me there was a TSB on the problem[/color]
>
> I couldn't find that Toyota TSB for the 1998 4Runner but I did find[/color]
that[color=blue]
> the main cause of brake shimmy is brake material buildup on the[/color]
rotors.[color=blue]
>
> [url]http://www.zeckhausen.com/avoiding_brake_judder.htm[/url]
> says "Despite the popular myth, brake judder is not caused by warped
> rotors. Judder is the result of a thickness variation in pad buildup[/color]
on[color=blue]
> the rotors' surfaces."
>
> So, I'm replacing the pads and rotors but that is not a long term[/color]
solution.[color=blue]
> I need to find how to test and eliminate the four pistons from[/color]
sticking in[color=blue]
> the caliper. Pads won't solve the problem. Since nobody can tell the
> quality of aftermarket pads (which was proven in the preceeding[/color]
threads)[color=blue]
> I'm going OEM (it's the only way one can go and have any given truth)[/color]
which[color=blue]
> means the brake shudder will likely re-occur at the 50,000 mile mark
> regularly unfortunately.
>
> There's no other way as far as we can see yet.
> Stu
>[/color]



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"Stuart A. Bronstein" <spamtrap@lexregia.com> wrote in message
news:ROLOf.44917$H71.36076@newssvr13.news.prodigy.com...[color=blue]
> "Spaceman" <Realspace@comcast.not> wrote in
> news:fZmdnULG7r9C3JbZRVn-pg@comcast.com:[color=green]
>> Brake rotors DO warp.
>> The "warping" also known as "lateral runout", is caused mostly
>> by an incorrect tightening of lugnuts when a tire/wheel is changed.
>> It can also (rarely) be caused by overheating in areas where the rotor
>> has a problem with uneven cooling such as blocked vent holes
>> If a proper brakejob is done, and you ALWAYS tighten lugnuts
>> correctly. no problem will arise later except the fact you will need
>> to replace worn pads and "worn" rotors.
>> Rotors also wear so later on you will need to replace them also.[/color]
>
> Hi James,
>
> I understand that rotors "can" wear out once they reach their wear limit.
>
> However, it's interesting that everyone "says" the wear limit is for heat
> dissipation but (according to the articles I've quoted), it's not. The
> wear
> limit is imposed to reduce the risk of the pistons falling out. Amazing.
> What I've thought for so many years is wrong.
>
> In addition, I've also learned that while I could true the rotors, I
> should
> (and will) replace the rotors and the pads with OEM rotors and pads,
> mainly
> because there are absolutely no standards that aftermarket rotors and pads
> have to meet yet which OEM braking systems must meet (FMVSS 105 and FMVSS
> 135 for example).
>
> Furthermore, I've learned that I should go to one of the two best Internet
> Toyota dealerships because they offer OEM parts at more than 25% less than
> my three closest Toyota dealerships did (I checked a dozen suppliers and
> found this to be true. In fact, one local dealership charged 5% MORE than
> list! Obviously I'll never go to him for parts!).
>
> However, even after all that research, I've learned that the brake judder
> (aka brake shudder, shimmy, vibration, pedal pulsation, etc) problem WILL
> RETURN if the real cause is the brake pistons sticking in their calipers.
>
> So, if the root cause is really do to the brake pistons "sticking", then
> I'll have the problem all over again in a few thousand miles! So, now I've
> moved on to researching how to tell if a piston is sticking (see a
> separate
> thread on that which concludes, so far, there is no instrument out there
> that will provide measurable values for brake piston sticking).
>
> The net is that if I just do as you said, then I could get the brake
> judder
> again in just a few thousand miles. That's why I'm doing all this
> research!
>
> Thanks for all your help for me and others,
> Stu[/color]

Stu

I thought you would have fixed this problem by now but I see that isn't
so. It is time for some friendly advice.

1. You are over analyzing your brake problem. Most of the web sites you are
reading stating that rotors don't warp are just plain wrong. Rotors and
drums can and will warp causing a pulsation when braking. Some ( most ) of
these sites seem to apply to RACE VEHICLES and DO NOT APPLY to street driven
vehicles.

2. You have a brake pulsation at highway speeds. This is a fact, it happens
when you apply the brakes.

3. Your brake pulsation is either caused by warped rotors or warped drums,
if equipped with drums in rear.

First step you need to take is to determine if the pulsation is coming
from the front or rear of the vehicle.

1. Drive vehicle at speed needed to cause pulsation and apply brakes. Is
pulsation felt in steering wheel ( does steering wheel shake side to side )?
If yes, the problem is with the front brakes.

Is the pulsation felt in the seat of your pants. If yes, it is most
likely coming from the rear brakes.

2. To determine front from rear, GENTLY and SLOWLY apply the rear brakes
ONLY, by using the parking brake. You are not trying to lock the rear
brakes. You are trying to see if the pulsation is being caused by warped
rear drums.Being you are applying the rear brakes only, any pulsation felt
would have to be coming from the rear brakes. NOTE: This only works if you
have rear drums. It may or may not work for rear discs depending on the
setup.If you get a pulsation from the rear brakes you need to take care of
that problem first. If you get no pulsation from the rears using the parking
brake your problem is up front.

You wonder if your caliper pistons are sticking. No they are not. How
can YOU tell ? Simple. You state that you have plenty of brake pad material
left. If your calipers were sticking you would have accelerated brake pad
wear and/or uneven brake pad wear from side to side. You have neither.

But how can you be sure, you ask? Simple. Take vehicle for a short ride
and make a few normal stops.Park on level ground. Raise both front tires off
the ground. Rotate tires by hand and see how freely they turn. You should be
able to rotate both tires freely. You should feel a slight drag from the
brake pads rubbing the rotors. This is normal for disc brakes and the amount
of drag felt varies by vehicle. Rotational effort should be about the same
for both sides.

Do both wheels turn freely without exessive drag ? If yes, you do not
have a caliper problem.

From what you have posted I would check your rear brake drums for warpage
using the parking brake test above. If you get no pulstaion from the rears
then it has to be caused by the front rotors, have them machined or replace
them.

Which brake pads to use ? You can't go wrong with factory brake pads, they
were designed to work on that vehicle. Aftermarket brake pads may not work
as well. Most aftermarket parts stores sell the cheapest line of brake pads
so they can advertise the lowest price. These cheaper pads will not work as
well as a premium pad. I have tried many brake pads over the years, some
worked well, some not so well ( as in noticebly reduced brake performance
and/or noisy brakes ). I have never had a problem using factory pads.

Hope this helps in getting you brake problem fixed.

Mike

"Mike" <mcarpe@frontiernet.net> wrote in
news:P1%Of.1902$kg.598@news02.roc.ny:[color=blue]
> I thought you would have fixed this problem by now but I see that
> isn't so. It is time for some friendly advice.
> First step you need to take is to determine if the pulsation
> is coming from the front or rear of the vehicle.[/color]

Hi Mike,

Thanks! For me and for the hundreds or more who will read this. You have
been a great help. Especially in the more practical matters.

Thanks to your problem-isolation technique with the parking brake, I
isolated the shudder/judder/shimmy/vibration with resultant pedal
pulsation to the front axle.

Then, on the advice of posters here, I bought OEM rotors and pads from
the recommended Internet Toyota dealership. I'm waiting for them to
arrive. Now that my main body of research is done, I'll finish the
simple brake job this weekend.

I'm currently researching the various types of grease to use for a
proper brake job (eg it seems to be a different grease for the anti-
squeal shims than for the holding pins and rubber seals than for the
wheel bearings, etc).
[color=blue]
> You wonder if your caliper pistons are sticking. No they are not.
> How can YOU tell ? Simple.
> You state that you have plenty of brake pad material left.[/color]

Interesting point. This makes sense. That's the kind of good diagnosis
idea I was looking for!
[color=blue]
> Rotate tires by hand and see how freely they turn.[/color]
Another interesting test. I jacked up the truck today for a quick look
in the dark and the wheels spun quite freely! I think this is another
good testing method. Thanks. That's what we were looking for!
[color=blue]
> Which brake pads to use ?
> You can't go wrong with factory brake pads.[/color]

Yes. I agree. Since there are no standards whatsoever for aftermarket
pads, the only way to go for me is OEM (Akebono) from an Internet aware
Toyota dealership. There is no other logical way except by trial & error
testing which I can't afford to do. Consumer Reports found that the most
important factor in braking was not the pads but MATCHING of the pads
(front to rear). No other factor was as important as using the same
brand and composition in the front and rears according to the CR tests I
read at the library this weekend.
[color=blue]
> Hope this helps in getting you brake problem fixed.
> Mike[/color]

Thanks Mike. Not only did you answer my questions, but the hundreds
(perhaps thousands?) of mechanics who follow these threads also learned
from the experts!

Thank you!
Stu

Stuart A. Bronstein wrote:
snip[color=blue]
> I'm currently researching the various types of grease to use for a
> proper brake job (eg it seems to be a different grease for the anti-
> squeal shims than for the holding pins and rubber seals than for the
> wheel bearings, etc).
>[/color]
snip

After cleaning parts with brass brushes (do not use a brush on a highly
polished surface like a piston or some slide pins) and solvent, you need a
brake lube for the shims, slides and/or pins. Don't use an excessive amount
on slides or shims as it can get on brake rotor.
After cleaning wheel bearings you need a wheel bearing grease for them. Do
you know how to pack a wheel bearing?
davidj92