Exploding Rotors: why you do not drill

[Fred Munro]

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
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"They that give up essential liberty to obtain temporary
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