Hanging rear caliper Bernie says:

[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.

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.
-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
>