Exploding Rotors: why you do not drill

[Bo Young]

> Looks like in this application they went for the more holes is better
> approach and the irregular pattern (yeah, I know it repeats so it's a
> regular pattern but you know what I mean) is driven by having to avoid the
> internal vent vanes.

Irregular patter to avoid vent vanes... good theory, and makes a lot of
sense, but I don't think that's the only reason.  For example, you see lots
of irregularly drilled rotors on motorcycles that aren't vented... no vents,
no vanes, nothing to avoid.

 Do you think there'd be any validity to a theory that the pattern is
irregular for the same reason that tire tread block sizes are irregular: to
break up the repeating patterns that cause hums and vibrations?  Hums are
just noisy and annoying on tires, but I can imagine that hitting the
fundamental resonance frequency on a brake rotor might have fairly
catasrophic consequences.

~Bo

----- Original Message -----
From: "Bob Rossato" <bob.rossato at att.net>
To: "Fred Munro" <munrof at sympatico.ca>; "Brett Dikeman" <brett at cloud9.net>;
<quattro at audifans.com>
Cc: "Steve Marinello" <smarinello at charter.net>
Sent: Friday, June 20, 2003 11:12 PM
Subject: RE: Exploding Rotors: why you do not drill


> Thanks for reaffirming that I'm not seeing things, Fred.  Unless we both
> are.  That's exactly the photo I based my comment on.  Funny but I didn't
> receive Brett's reply to my post.  Neither the one directly to me nor the
> one to the list.  I was wondering why all the follow on comments
referenced
> Zimmerman rotors.  Maybe it'll show up tomorrow.
>
> In any case.  This is what I'm typically used to seeing with regard to
> drilled rotors (http://home.attbi.com/~jbipes/ttr/frntrotors.html).
Scroll
> down the series of photos on the left side frame and there are a few of
> Zimmerman x-drilled TT rotors.  Simple symmetrical spiral pattern.
>
> But admittedly, I'm not an expert on drilled rotors and in my browsing I
> found this site (http://www.evoms.com/vw%20brake%20page.htm) that shows
what
> appears to be the same irregular pattern as that on the failed rotor (Look
> at the Level 3 brakes).  So, it seems I have to recant my comment about it
> being a home made hack job.  I guess it's a factory hack job ;-)  I guess
> that only seeing a small part of the rotor made the pattern indiscernible.
> Looks like in this application they went for the more holes is better
> approach and the irregular pattern (yeah, I know it repeats so it's a
> regular pattern but you know what I mean) is driven by having to avoid the
> internal vent vanes.  I agree with Fred.  The end result is holes that are
> too close together in some places.
>
> Bob
>
>
> > -----Original Message-----
> > From: quattro-admin at audifans.com [mailto:quattro-admin at audifans.com]On
> > Behalf Of Fred Munro
> > Sent: Friday, June 20, 2003 9:48 PM
> > To: Brett Dikeman; Bob Rossato; quattro at audifans.com
> > Cc: Steve Marinello
> > Subject: RE: Exploding Rotors: why you do not drill
> >
> >
> > Hmmm, I think Bob may have a point, Brett. Looking at your photo 2743,
> > something seems terribly wrong with the hole spacing. They may be
> > Zimmerman
> > rotors, but Zimmerman may not have drilled them. Most drilled rotors
have
> > the holes in a spiral pattern following the internal vent between the
fins
> > (i.e. Porsche 996 rotors). The holes on the rotor fragment seem random
and
> > some are way too close together (third from left, bottom row and
> > the hole to
> > it's right and slightly above for example). I can't claim to be a rotor
> > cross-drilling expert, but from a structural viewpoint that's not the
way
> > I'd think it should be done.
> > If some bonehead is punching holes in rotors and selling them as
> > "cross-drilled", he needs a good swift kick in the a$$. This failure
could
> > also happen on a busy freeway or two lane with more tragic consequences.
> >
> > Interesting story and photos - thanks for sharing them.
> >
> > Fred Munro
> > '94 S4 (solid Zimmerman rotors - OK,OK, they're a little rusty
> > and worn, but
> > no holes yet)
> >
> > -----Original Message-----
> > From: quattro-admin at audifans.com [mailto:quattro-admin at audifans.com]On
> > Behalf Of Brett Dikeman
> > Sent: June 20, 2003 11:55 AM
> > To: Bob Rossato; quattro at audifans.com
> > Cc: Steve Marinello
> > Subject: RE: Exploding Rotors: why you do not drill
> >
> >
> > At 7:41 AM -0400 6/20/03, Bob Rossato wrote:
> > >Not to start a thread on pros and cons of drilled rotors but, it is
> > >obvious that these rotors were a home made job.  There is a rudimentary
> > >pattern to the holes but the spacing is all over the place and the
holes
> > >look bigger than anything else I've seen.  I'm not defending drilled
> > >rotors but the reason these exploded has a lot more to do with the fact
> > >that some clueless individual just went to town on them with a drill
> > >press without any regard to the size of the holes, amount of material
> > >removed, or balance of the rotor.  If someone is actually selling these
> > >things in this condition then that is downright criminal.
> >
> > They were Zimmerman rotors, made in Germany; not a homemade job.
> > Their rotors seem to be widely sold by VW/Audi/Porsche 'performance
> > shops' on the net.
> >
> > In person they appeared to be drilled in a perfectly even pattern,
> > consistent hole size, so on etc.  Also, if they were not balanced,
> > one thinks the TT owner would have noticed immediately at 120+ mph on
> > the front straight.
> >
> > B
> > --
> > ----
> > "They that give up essential liberty to obtain temporary
> > safety deserve neither liberty nor safety." - Ben Franklin
> > http://www.users.cloud9.net/~brett/
> >
> >
>
>