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Likely causes of vibration when braking?



 
 
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  #1  
Old April 21st 08, 06:29 PM posted to rec.autos.tech
TomO[_1_]
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Posts: 68
Default Likely causes of vibration when braking?

I'm dealing with a 1994 Toyota 4Runner with the 3.slow engine and about
190k miles on the chassis.

Lately and increasingly, there is a *lot* of vibration when braking from
over 40mph or so. I believe that this comes from the front end because I
tried applying just the parking brake at speed. In that test, it stopped
smoothly.

I lifted the front end and did a good old fashioned wiggle test, but
found nothing noticeably loose. I also lightly applied the brakes while
rotating each wheel by hand. The grab seemed smooth, but I'm not real
sure if this would be a good test for a warped rotor.

What, in your collective, esteemed opinion would be the likely causes
for a rather violent shaking of the front end when braking? BTW - the
brake pads are still in good shape, although I didn't measure them, but
there is plenty of meat left.

--
TomO
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  #2  
Old April 21st 08, 06:57 PM posted to rec.autos.tech
Mike
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Posts: 349
Default Likely causes of vibration when braking?


"TomO" > wrote in message
...
> I'm dealing with a 1994 Toyota 4Runner with the 3.slow engine and about 190k
> miles on the chassis.
>
> Lately and increasingly, there is a *lot* of vibration when braking from
> over 40mph or so. I believe that this comes from the front end because I
> tried applying just the parking brake at speed. In that test, it stopped
> smoothly.
>
> I lifted the front end and did a good old fashioned wiggle test, but found
> nothing noticeably loose. I also lightly applied the brakes while rotating
> each wheel by hand. The grab seemed smooth, but I'm not real sure if this
> would be a good test for a warped rotor.
>
> What, in your collective, esteemed opinion would be the likely causes for a
> rather violent shaking of the front end when braking? BTW - the brake pads
> are still in good shape, although I didn't measure them, but there is plenty
> of meat left.
>
> --
> TomO


Warped front brake rotors. Have them machined if they are thick enough or
replace them if they are too thin to machine.

  #3  
Old April 21st 08, 07:32 PM posted to rec.autos.tech
HLS
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Posts: 1,418
Default Likely causes of vibration when braking?


"TomO" > wrote in message
...

> I lifted the front end and did a good old fashioned wiggle test, but found
> nothing noticeably loose. I also lightly applied the brakes while rotating
> each wheel by hand. The grab seemed smooth, but I'm not real sure if this
> would be a good test for a warped rotor.
>
> What, in your collective, esteemed opinion would be the likely causes for
> a rather violent shaking of the front end when braking? BTW - the brake
> pads are still in good shape, although I didn't measure them, but there is
> plenty of meat left.
>

It could be a warped or varying thickness rotor, but it could also be loose
or worn front end parts.

If it is due to an out of spec rotor, you will usually feel a characteristic
shudder.
If it is a varying thickness problem, you will feel it through the brake
pedal. If it
is a warped rotor, you will also feel it, but it may be somewhat different.

You can measure the runout and thickness variation of rotors and know for
sure
how badly they are off.

I have, however, also seen cars with worn ball joints or rod ends that will
start
buffeting when some braking stress is put on the car. You might want to be
sure
that the front suspension and steering parts are in good shape.

  #4  
Old April 21st 08, 08:57 PM posted to rec.autos.tech
Thomas Tornblom
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Posts: 80
Default Likely causes of vibration when braking?

It may be over-torqued lug nuts/bolts, especially if you have allow rims.
  #5  
Old April 21st 08, 09:19 PM posted to rec.autos.tech
TomO[_1_]
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Posts: 68
Default Likely causes of vibration when braking?

HLS wrote:
>
> "TomO" > wrote in message
> ...
>
>> I lifted the front end and did a good old fashioned wiggle test, but
>> found nothing noticeably loose. I also lightly applied the brakes
>> while rotating each wheel by hand. The grab seemed smooth, but I'm not
>> real sure if this would be a good test for a warped rotor.
>>
>> What, in your collective, esteemed opinion would be the likely causes
>> for a rather violent shaking of the front end when braking? BTW - the
>> brake pads are still in good shape, although I didn't measure them,
>> but there is plenty of meat left.
>>

> It could be a warped or varying thickness rotor, but it could also be loose
> or worn front end parts.
>
> If it is due to an out of spec rotor, you will usually feel a
> characteristic shudder.
> If it is a varying thickness problem, you will feel it through the brake
> pedal. If it
> is a warped rotor, you will also feel it, but it may be somewhat different.
>
> You can measure the runout and thickness variation of rotors and know
> for sure
> how badly they are off.
>
> I have, however, also seen cars with worn ball joints or rod ends that
> will start
> buffeting when some braking stress is put on the car. You might want
> to be sure
> that the front suspension and steering parts are in good shape.


I'll try and get a gauge that can show me the runout/thickness first. Is
there something not-too-costly that's readily available?
  #6  
Old April 21st 08, 10:11 PM posted to rec.autos.tech
HLS
external usenet poster
 
Posts: 1,418
Default Likely causes of vibration when braking?


"TomO" > wrote in message news:480cf6bb$0$89867
>
> I'll try and get a gauge that can show me the runout/thickness first. Is
> there something not-too-costly that's readily available?


You use a micrometer which has a wide enough mouth so that you can take
readings at several placed if you want to measure thickness variations.
Runout can be measured
with a dial indicator. The hobbyist mechanic is not likely to have both
these.

If you take it to a professional mechanic, you have to be careful to find
someone who
will check it out, not just throw money at it.

While it is likely that rotor distortion or wear is the problem, I just
wanted to make a point
that other things can also cause similar shuddering.

There used to be a really good article on brake rotor issues, and if I can
still find it I will post
it here for you. Read it until you really understand what they are saying,
and you will be well
armed to discuss with a professional mechanic.

Other points...never never never let anyone put your wheels back on the car
with an impact
wrench. EVEN if they say that they are using a Torq Stick, dont allow it.

If the mechanic doesnt true the rotor properly, or replace them with new
rotors which
are properly prepared, this problem can recur.

Anyway, read the article (as soon as I find it)

  #7  
Old April 21st 08, 10:20 PM posted to rec.autos.tech
HLS
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Posts: 1,418
Default Likely causes of vibration when braking?


"TomO" > wrote in message
...
> I'm dealing with a 1994 Toyota 4Runner with the 3.slow engine and about
> 190k miles on the chassis.


Here is that link, TomO
http://www.babcox.com/editorial/bf/bf100326.htm

  #8  
Old May 19th 08, 09:36 PM posted to rec.autos.tech
TomO[_1_]
external usenet poster
 
Posts: 68
Default Likely causes of vibration when braking?

TomO wrote:
> I'm dealing with a 1994 Toyota 4Runner with the 3.slow engine and about
> 190k miles on the chassis.
>
> Lately and increasingly, there is a *lot* of vibration when braking from
> over 40mph or so. I believe that this comes from the front end because I
> tried applying just the parking brake at speed. In that test, it stopped
> smoothly.
>
> I lifted the front end and did a good old fashioned wiggle test, but
> found nothing noticeably loose. I also lightly applied the brakes while
> rotating each wheel by hand. The grab seemed smooth, but I'm not real
> sure if this would be a good test for a warped rotor.
>
> What, in your collective, esteemed opinion would be the likely causes
> for a rather violent shaking of the front end when braking? BTW - the
> brake pads are still in good shape, although I didn't measure them, but
> there is plenty of meat left.
>


One new pair of rotors later, the problem is either fixed or masked for
a while. I did make sure that the surfaces where the rotor bolts to the
hub were good-n-clean and that the rotors seated fully against that hub
mating surface.

I replaced both rotors because the parts were cheap enough. This also
gave me the opportunity to repack the wheel bearings and all. The parts
I removed ( pads, rotors ) were not terribly worn, but one of them must
have been severely warped.

I guess that only time will at this point.
  #9  
Old May 20th 08, 01:26 PM posted to rec.autos.tech
C. E. White[_1_]
external usenet poster
 
Posts: 933
Default Likely causes of vibration when braking?

"Google" lining transfer.

Ed

"TomO" > wrote in message
...
> TomO wrote:
>> I'm dealing with a 1994 Toyota 4Runner with the 3.slow engine and
>> about 190k miles on the chassis.
>>
>> Lately and increasingly, there is a *lot* of vibration when braking
>> from over 40mph or so. I believe that this comes from the front end
>> because I tried applying just the parking brake at speed. In that
>> test, it stopped smoothly.
>>
>> I lifted the front end and did a good old fashioned wiggle test,
>> but found nothing noticeably loose. I also lightly applied the
>> brakes while rotating each wheel by hand. The grab seemed smooth,
>> but I'm not real sure if this would be a good test for a warped
>> rotor.
>>
>> What, in your collective, esteemed opinion would be the likely
>> causes for a rather violent shaking of the front end when braking?
>> BTW - the brake pads are still in good shape, although I didn't
>> measure them, but there is plenty of meat left.
>>

>
> One new pair of rotors later, the problem is either fixed or masked
> for a while. I did make sure that the surfaces where the rotor bolts
> to the hub were good-n-clean and that the rotors seated fully
> against that hub mating surface.
>
> I replaced both rotors because the parts were cheap enough. This
> also gave me the opportunity to repack the wheel bearings and all.
> The parts I removed ( pads, rotors ) were not terribly worn, but one
> of them must have been severely warped.
>
> I guess that only time will at this point.


  #10  
Old May 20th 08, 02:55 PM posted to rec.autos.tech
Calab
external usenet poster
 
Posts: 88
Default Likely causes of vibration when braking?

> "Google" lining transfer.

???

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[PDF] Colorado River Water Transfer Agreements...

[PDF] Quantification Settlement Agreement...

Linings for crucible furnaces and transfer vessels and method of ...

Linings for crucible furnaces and transfer vessels and method of ...

Teflon ® PTFE Compression Molding, PFA Transfer Molding, PCTFE ...

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