Shimmy while braking.. "You make the diagnosis"

Hello all...

My 2001 GT has a shimmy while braking at highway speeds. It is felt in the
steering wheel. This shimmy is not being caused by a warped rotor. Also...
The tires are new and the pressure is perfect. I'm taking the car in to the
dealer this Tuesday, but I figured I'd make a post and play "You Make The
Diagnosis". I'm almost sure I know what it is, but I'll I wont say.

Anyone wanna take a guess at what it is ???

I'll post the dealer's findings when I get the car back Tuesday night.

Regards !!!

Mike...

Michael wrote:
> Hello all...
>
> My 2001 GT has a shimmy while braking at highway speeds. It is felt in the
> steering wheel. This shimmy is not being caused by a warped rotor. Also...
> The tires are new and the pressure is perfect. I'm taking the car in to the
> dealer this Tuesday, but I figured I'd make a post and play "You Make The
> Diagnosis". I'm almost sure I know what it is, but I'll I wont say.
>
> Anyone wanna take a guess at what it is ???
>
> I'll post the dealer's findings when I get the car back Tuesday night.
>
> Regards !!!
>
> Mike...
>
>

Warped rotor(s).

Rob

1 of the tires. just cause there new don`t make them not be the problem.
my 99 f-150 came out of the factor with a bad goodyear tire on it.
around 65-70 mph the right front had a bad shake to it. come to find it
had a flat spot on it. the dealer put on a new one and everything was
fine. mp

"trainfan1" > wrote in message
et...
> Michael wrote:
>> Hello all...
>>
>> My 2001 GT has a shimmy while braking at highway speeds. It is felt in
>> the steering wheel. This shimmy is not being caused by a warped rotor.
>> Also... The tires are new and the pressure is perfect. I'm taking the car
>> in to the dealer this Tuesday, but I figured I'd make a post and play
>> "You Make The Diagnosis". I'm almost sure I know what it is, but I'll I
>> wont say.
>>
>> Anyone wanna take a guess at what it is ???
>>
>> I'll post the dealer's findings when I get the car back Tuesday night.
>>
>> Regards !!!
>>
>> Mike...
>
> Warped rotor(s).
>

Not a rotor(s) If you have warped rotors what you would feel is a hard
regular knocking type of pulsation. And you'd feel it in the break pedal.
Also.. The pulsation from a warped rotor tends to be noticeable at just
about all speeds above say 20-30 MPH.

Mike

Michael wrote:
> Hello all...
>
> My 2001 GT has a shimmy while braking at highway speeds. It is felt in the
> steering wheel. This shimmy is not being caused by a warped rotor. Also...
> The tires are new and the pressure is perfect. I'm taking the car in to the
> dealer this Tuesday, but I figured I'd make a post and play "You Make The
> Diagnosis". I'm almost sure I know what it is, but I'll I wont say.
>
> Anyone wanna take a guess at what it is ???
>
> I'll post the dealer's findings when I get the car back Tuesday night.
>
> Regards !!!
>
> Mike..

My 2001 GT had the same prolem until I changed tires. New tires,
problem eliminated

Philoman.

Now there's a missed assumption if I ever saw one... Rotors can suffer from
warp or a parallelism problem... the affects can be un-noticeable at
moderate speeds/braking effort and still be quite violent at higher speeds.
Sometimes the affects are more noticeable in the pedal - sometimes in the
steering wheel and sometimes in the feel of the car itself....

You are "almost sure" you know the concerns cause..... after almost 40 years
of doing this, I have realized that "almost sure" isn't much better than "I
dunno" - nothing is written in stone and vibration diagnosis with such
little information is nearly impossible (and is usually coupled with a
statement like "I forgot to add....)

"Michael" > wrote in message
news
>
> "trainfan1" > wrote in message
> et...
>> Michael wrote:
>>> Hello all...
>>>
>>> My 2001 GT has a shimmy while braking at highway speeds. It is felt in
>>> the steering wheel. This shimmy is not being caused by a warped rotor.
>>> Also... The tires are new and the pressure is perfect. I'm taking the
>>> car in to the dealer this Tuesday, but I figured I'd make a post and
>>> play "You Make The Diagnosis". I'm almost sure I know what it is, but
>>> I'll I wont say.
>>>
>>> Anyone wanna take a guess at what it is ???
>>>
>>> I'll post the dealer's findings when I get the car back Tuesday night.
>>>
>>> Regards !!!
>>>
>>> Mike...
>>
>> Warped rotor(s).
>>
>
> Not a rotor(s) If you have warped rotors what you would feel is a hard
> regular knocking type of pulsation. And you'd feel it in the break pedal.
> Also.. The pulsation from a warped rotor tends to be noticeable at just
> about all speeds above say 20-30 MPH.
>
> Mike
>

"Jim Warman" > wrote in message
news:U8wDg.2890$395.2488@edtnps90...
> Now there's a missed assumption if I ever saw one... Rotors can suffer
> from warp or a parallelism problem... the affects can be un-noticeable at
> moderate speeds/braking effort and still be quite violent at higher
> speeds. Sometimes the affects are more noticeable in the pedal - sometimes
> in the steering wheel and sometimes in the feel of the car itself....

In this case, there is NO sensation what so ever in the pedal. Not even a
hint regardless of the amount of pressure applied to the pedal. Also... I
did write that warped rotors "TEND" to be noticeable at above 20-30 mph. I
didn't say that they all warped rotors characteristically were noticeable at
speeds over 20-30 mph. I'm also saying that I don't think my shimmy
problem is being caused by a warped rotor. If that turns out to be the case
though, I'll surely own up to it.


> You are "almost sure" you know the concerns cause..... after almost 40
> years of doing this, I have realized that "almost sure" isn't much better
> than "I dunno" - nothing is written in stone and vibration diagnosis with
> such little information is nearly impossible (and is usually coupled with
> a statement like "I forgot to add....)


No question about it. "Almost sure" of what the problem is has played
itself out thousands upon thousands of times to the tune of all sorts of
wasted time. Not to mention, all the perfectly good parts that were
unessasrarly replaced ! I don't have 40 years of pro experience under my
belt like you do. I have about four meager years pro experience. Add to
that, it has been since 1991 that I repaired cars professionally. I worked
my way through college working in a repair shop. Before that, I had auto
shop in high school. My Jr. and Sr. years in high school, I built and raced
a street rod. So.... My experience is modest and you make a good point, but
I think I did give enough info so that anyone who wanted to could have fun
and take a few educated guesses at what is going on.

At any rate... Do you have a likely culprit for the problem or are you
refusing to take a stab at it due to the limited info I have given ??? I
mean... What the hell ??? It couldent hurt to have a bit of fun...

Michael

>
> "Michael" > wrote in message
> news
>>
>> "trainfan1" > wrote in message
>> et...
>>> Michael wrote:
>>>> Hello all...
>>>>
>>>> My 2001 GT has a shimmy while braking at highway speeds. It is felt in
>>>> the steering wheel. This shimmy is not being caused by a warped rotor.
>>>> Also... The tires are new and the pressure is perfect. I'm taking the
>>>> car in to the dealer this Tuesday, but I figured I'd make a post and
>>>> play "You Make The Diagnosis". I'm almost sure I know what it is, but
>>>> I'll I wont say.
>>>>
>>>> Anyone wanna take a guess at what it is ???
>>>>
>>>> I'll post the dealer's findings when I get the car back Tuesday night.
>>>>
>>>> Regards !!!
>>>>
>>>> Mike...
>>>
>>> Warped rotor(s).
>>>
>>
>> Not a rotor(s) If you have warped rotors what you would feel is a hard
>> regular knocking type of pulsation. And you'd feel it in the break
>> pedal. Also.. The pulsation from a warped rotor tends to be noticeable
>> at just about all speeds above say 20-30 MPH.
>>
>> Mike
>>
>
>

Sounds like a broken belt in one of your tires....


"Michael" > wrote in message
...
> Hello all...
>
> My 2001 GT has a shimmy while braking at highway speeds. It is felt in
> the steering wheel. This shimmy is not being caused by a warped rotor.
> Also... The tires are new and the pressure is perfect. I'm taking the car
> in to the dealer this Tuesday, but I figured I'd make a post and play "You
> Make The Diagnosis". I'm almost sure I know what it is, but I'll I wont
> say.
>
> Anyone wanna take a guess at what it is ???
>
> I'll post the dealer's findings when I get the car back Tuesday night.
>
> Regards !!!
>
> Mike...
>

First thing I'd do is grab the brake rotor caliper and the dial
indicator.... Measure the radial runout of the rotors. Next, measure the
thickness of the rotor in several places, looking for variations in both
instances....

FWIW, some (of those techs that do take this sort of pride in their work)
will measure in three or 4 places..... For the time it takes, I prefer to
measure in line with each wheel stud both at the outer and inner perimeter
of the rotor....

Other rotor concerns include poor machine finish (when discussing refinished
rotors).... If the lathe is set to take too coarse of a cut, some pads can
actually be forced along the resulting 'threads' in a "stick/slip" type of
feel - may or may not be felt in the pedal and sometimes can be quite
noisey. Some brake rotors can develop burnished areas that can give a
surging feeling when stopping - also without giving a feel to the pedal...

Without the benefit of a test drive, I'm at a disadvantage but (from your
initial description) rotors are the place to start.


"Michael" > wrote in message
...
>
> "Jim Warman" > wrote in message
> news:U8wDg.2890$395.2488@edtnps90...
>> Now there's a missed assumption if I ever saw one... Rotors can suffer
>> from warp or a parallelism problem... the affects can be un-noticeable at
>> moderate speeds/braking effort and still be quite violent at higher
>> speeds. Sometimes the affects are more noticeable in the pedal -
>> sometimes in the steering wheel and sometimes in the feel of the car
>> itself....
>
> In this case, there is NO sensation what so ever in the pedal. Not even a
> hint regardless of the amount of pressure applied to the pedal. Also... I
> did write that warped rotors "TEND" to be noticeable at above 20-30 mph.
> I didn't say that they all warped rotors characteristically were
> noticeable at speeds over 20-30 mph. I'm also saying that I don't think
> my shimmy problem is being caused by a warped rotor. If that turns out to
> be the case though, I'll surely own up to it.
>
>
>> You are "almost sure" you know the concerns cause..... after almost 40
>> years of doing this, I have realized that "almost sure" isn't much better
>> than "I dunno" - nothing is written in stone and vibration diagnosis with
>> such little information is nearly impossible (and is usually coupled with
>> a statement like "I forgot to add....)
>
>
> No question about it. "Almost sure" of what the problem is has played
> itself out thousands upon thousands of times to the tune of all sorts of
> wasted time. Not to mention, all the perfectly good parts that were
> unessasrarly replaced ! I don't have 40 years of pro experience under my
> belt like you do. I have about four meager years pro experience. Add to
> that, it has been since 1991 that I repaired cars professionally. I
> worked my way through college working in a repair shop. Before that, I
> had auto shop in high school. My Jr. and Sr. years in high school, I
> built and raced a street rod. So.... My experience is modest and you make
> a good point, but I think I did give enough info so that anyone who wanted
> to could have fun and take a few educated guesses at what is going on.
>
> At any rate... Do you have a likely culprit for the problem or are you
> refusing to take a stab at it due to the limited info I have given ??? I
> mean... What the hell ??? It couldent hurt to have a bit of fun...
>
> Michael
>
>>
>> "Michael" > wrote in message
>> news
>>>
>>> "trainfan1" > wrote in message
>>> et...
>>>> Michael wrote:
>>>>> Hello all...
>>>>>
>>>>> My 2001 GT has a shimmy while braking at highway speeds. It is felt
>>>>> in the steering wheel. This shimmy is not being caused by a warped
>>>>> rotor. Also... The tires are new and the pressure is perfect. I'm
>>>>> taking the car in to the dealer this Tuesday, but I figured I'd make a
>>>>> post and play "You Make The Diagnosis". I'm almost sure I know what
>>>>> it is, but I'll I wont say.
>>>>>
>>>>> Anyone wanna take a guess at what it is ???
>>>>>
>>>>> I'll post the dealer's findings when I get the car back Tuesday night.
>>>>>
>>>>> Regards !!!
>>>>>
>>>>> Mike...
>>>>
>>>> Warped rotor(s).
>>>>
>>>
>>> Not a rotor(s) If you have warped rotors what you would feel is a hard
>>> regular knocking type of pulsation. And you'd feel it in the break
>>> pedal. Also.. The pulsation from a warped rotor tends to be noticeable
>>> at just about all speeds above say 20-30 MPH.
>>>
>>> Mike
>>>
>>
>>
>
>

"trainfan1" > wrote in message
et...
> Michael wrote:
>> Hello all...
>>
>> My 2001 GT has a shimmy while braking at highway speeds. It is felt in
>> the steering wheel. This shimmy is not being caused by a warped rotor.
>> Also... The tires are new and the pressure is perfect. I'm taking the car
>> in to the dealer this Tuesday, but I figured I'd make a post and play
>> "You Make The Diagnosis". I'm almost sure I know what it is, but I'll I
>> wont say.
>>
>> Anyone wanna take a guess at what it is ???
>>
>> I'll post the dealer's findings when I get the car back Tuesday night.
>>
>> Regards !!!
>>
>> Mike...
>
> Warped rotor(s).
>
> Rob
loose or defective upper bushings