Hanging rear caliper Bernie says:

Bernie Benz b.benz at charter.net
Mon Apr 18 10:26:12 EDT 2005

I'm not objecting to your's or Scott's relating of your BTDT caliper
problems.  Rather, I was only disputing Scott's cause analysis of his
problem.  First, pointing out the inappropriateness of his dowel pin
analogy, inasmuch as the piston is not congruently guided by the caliper
bore.  Further, discounting his contention that piston guidance is acheived
in any way by the Ebrake nut and screw.

I do readily admit to a wrong analysis, and maybe I'm too quick to point out
those of others.  So, what have been your rear caliper problems and their
real causes?  Promise not to comment!

> From: Peter Schulz <pcschulz at comcast.net>
> Bernie:
> why is it when other people's BTDT conflicts with your's its considered BS?
> Both Scott and I had cases of rear calipers with working guide pins, even
> pad wear, and annually FLUSHED brake systems (required for Driver
> instruction training)
> Is is that difficult for you to admit that you may be wrong?
> It's evidently easy for you to quickly tell other people that they are.
> -Peter
> At 12:36 AM 4/18/2005, you wrote:
>> From: SuffolkD at aol.com
>> Bernie:  Just like a dowell extended far out of its hole, or any cylindrical
>> object pushed far enough out of its bore: will droop, sag,
>> whatever....that's physics.  Period.
> BS, Scott!   You must believe that gravity sucks it askew.  The piston will
> always align itself perpendicular with the pad's backing plate, a large
> contact area.
>> Furthermore, the quattro123.com link (
>> http://www.quattro123.com/200Brakes.htm) shows the internals of the caliper
>> and the coarse grooved "Thread" the piston winds in on.  No mystery
>> there......... Piston too far out and aligning the piston onto the "coarse
>> grooved "Thread"" is why the piston is hard to push back in, why its needed
>> to be "screwed" back in and why some people ake them off the car to a vise
>> for alignment during R&R.....................aligning the threads is a
>> challenge because its not a standard fine thread..........................
>> The metalnerd.com and similar Audi brake tools work well when the piston
>> isn't pushed too far out. Why DFI IAB isn't the best advice here IMHO.
> Oh, Scott!  Believe what you wish, but the the E-brake nut within the
> caliper piston is purposefully a floating nut relative to piston to bore
> alignment, and thus it has no effect on this alignment.
> Bernie
>> -Scott by BOSTON
>> In a message dated 4/18/2005 12:01:14 AM Eastern Daylight Time,
>> b.benz at charter.net writes:
>> From: SuffolkD at aol.com
>> snip.
>> Similarly, the piston when extended far out at near full travel will droop,
>> or cock out of alignment.  Seen that one.
>> Seen that one maybe, Scott, but IMO likely a wrong
>> conclusion on your part.  The piston is not guided by the caliper bore at
>> all, it is only suspended by the bore O-ring seal and its face contact with
>> the
>> pad backing plate surface.  Therefore, the piston could only cock if the
>> pad were to wear out of parallel with the backing plate surface to a high
>> degree, i.e. a highly tapered pad.  A most unlikely and self correcting
>> condition, one sufficient to cause piston contact and jamming within the
>> caliper
>> bore.  More likely, just a sludged up hydraulic system.  Fix it, it
>> ain't broke!
>> Bernie
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> 1991 200 20v Q Avant Indigo Mica
> 1991 90 20v Q Red
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