Brake Shimmy

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LeRoge - 29 Jul 2007 05:56 GMT

I recently had the rotors and calipers ( by different shops ) replaced
on my 2001 Econoline XL ( 5.4 L ). I was getting a slight
'pulsation' as I came to a stop. I was told the rotors were 'warped'
and the calipers needed replacement.

Now, 6000 miles later I have the same problem!!! As I come to a stop,
I feel a slight pulsation in braking...like one 'pulse' per wheel
rotation. As one might suspect, the shop that replaced the rotors
says the caliper(s) are bad - the shop that replace the calipers says
the rotors are warped! I don't believe either of them! I think the
real problem is related to the tie rods and perhaps the ball joints!
I do notice a tad bit of 'play' at the steering linkage to the tie
rod...similar to what I say a couple of years ago that resulted in
replacing the tie rods.

Could this really be a tie rod or ball joint problem??? How can I
confirm my suspicion?

Pleae advise.

LeRoge

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Ashton Crusher - 29 Jul 2007 07:41 GMT

I think it's the rotors. I've had it happen more then once that they
warp again within 6000 miles of replacement.

>I recently had the rotors and calipers ( by different shops ) replaced
>on my 2001 Econoline XL ( 5.4 L ). I was getting a slight
[quoted text clipped - 17 lines]
>
>LeRoge

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Mikepier - 29 Jul 2007 11:55 GMT

> I think it's the rotors. I've had it happen more then once that they
> warp again within 6000 miles of replacement.
[quoted text clipped - 22 lines]
>
> - Show quoted text -

Calipers don't usually warp. It's the rotors. Make sure your lugs nuts
are nut overtight, thats a common cause for warped rotors.

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Jim Warman - 29 Jul 2007 16:14 GMT

Why so many different shops involved in such a simple repair? As you are
finding out, this is a recipe for frustration on your part as the two shops
will sit back and say "not me" until any chances of a warrantable solution
are long past....

First, calipers will not cause a brake pulsation.... they can sieze, they
can corrode to the point where the pistons wont retract easily, they can be
damaged (torn seals, broken bleeders, chipped pistons) but the reason for
replacing them is always going to be readily identifiable....

The rotors, however, can make a bake pusation and they can be measured to
determine this..... First, the shop can check for parallelism of the swept
surfaces..... Rotor thickness is measured in four places around the
circumerance close to the outer edge.... Repeat these measurements close to
the inside edge and compare the readings.... Next will be the runout
check.... A dial indicator is used to measure rotor runout near the outer
edge of the swept area.

FWIW, Ford no longer publishes a spec on thickness variation or runout on
brake rotors - modern thinking is that if a pulsation is felt, we either
machine the offending rotors with an on-car lathe or we replace the rotors
if insufficient material is present for machining.

From memory.... the previous spec for rotor runout on Ford light trucks and
vans was 0.003".... I cannot recall the spec for parallel but I believeit
was lower than the spec for runout....

Bear in mind that improper wheel installation can affect brake pulsation
but, at the very least, the shop that sold and installed the rotors should
step up to the plate - if for no other reason than a show of goodwill.....

And you should stop flitting from shop to shop..... Finding a tech is much
like finding a family doctor.... Find one that you feel comfortable with -
one that will explain anything you don't understand - one that is truthful
and holds terms like honesy and integrity in high regard....

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