[200q20v] Re: [V8] just out of curiosity (UFO question)...

[Phil Rose]

A couple of listers (Graydon Stuckey and Jeff Bernstein) responded to 
my query with their guesses, which happen to agree with my own, 
secret guess--which I hadn't been confident enought to mention, 
fearing jeers of derision... :-)  Chris Miller claims he's found 
Audi's own description of the device--where, Chris? Maybe it's in the 
Album, I didn't look there.

Graydon wins (yeh, a  new S8, that's the ticket) for being first with 
a correct answer.

So--the conclusion is that this "thing"** is a "vibration damper", 
i.e., a counterweight used/needed to alter the resonant frequency of 
the caliper. Well, then that seems to tell us that Audi knew there 
was a special "problem" with the UFO design pretty much right out of 
the box, so-to-speak.

Now, I wonder if it's possible for a significant part of certain UFO 
vibration problems to be treated by modification of that caliper 
damping device? Sure, it would be best to have a perfect, non-warped 
rotor, but assuming some warpage is unavoidable, could vibration be 
further "supressed" to any useful extent by "tuning" the damper with 
some additional weight?  Has anyone tried that? Possibly it would be 
easier to completely remove the thing and check if the problem 
actually worsens. I assume it unscrews from the caliper body.

Also, if this damper is effective (and would Audi ever do something 
that's ineffective?), then owners would be well-advised to verify 
that it doesn't "go missing" or become damaged (bent).

Phil

** We might call this (pending approval by the ISO) the "UFO damper", 
unless Audi already has assigned it a convenient name.



At 3:39 PM -0500 1/31/01, Phil Rose wrote:
>Yesterday I was kibbitzing with a local Audi wrench (small-shop guy who
>likes to chat) while he completed a CV boot replacement on a '90 V8. While
>I was examining the UFO brake I noticed a strange-looking appendage (seemed
>to be stainless) which stuck out horizontally near the top (inside) end of
>the caliper. It has a thin shaft (tube?) that's about 1.5" long and it
>terminates in round, flat-ended "knob" of about 3/4" diameter.
>
>"Whazzzaaaat?", I asked.
>
>He smiled, and replied, "You tell me. I've been wondering for years about
>that thing."
>
>I looked in my Bentley and could see the "thing" clearly drawn in several
>UFO caliper diagrams, but there didn't seem to be any notation as to it's
>name or function.
>
>Anyone have a clue?
>
>Phil
>whose '91 200q doesn't even have UFO brakes
>
>
>Phil Rose
>Rochester, NY
>mailto:pjrose at frontiernet.net
>
>
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-- 

Phil Rose
Rochester, NY
mailto:pjrose at frontiernet.net