Exploding Rotors: why you do not drill

[Bo Young]

> I would challenge anyone to find pictures from a reputable site or brand
with discs which have
> been drilled in anything other than a symmetrical fashion...

http://www.harley-davidson.com/PR/MOT/2003/03_model_enlarge.asp?locale=en_US
&bmLocale=en_US&market=US&family=Softail&model=FXSTS&num=1

Drilled rotors do not have to have their holes in any clearly repeating
pattern.  They only need to have the center of mass be at the center of the
rotor ("balanced").

~Bo
----- Original Message -----
From: "Duncan Thomson" <duncan at systemcontrols.co.nz>
To: "Bob Rossato" <bob.rossato at att.net>; "Fred Munro" <munrof at sympatico.ca>;
<quattro at audifans.com>
Sent: Monday, June 23, 2003 2:36 AM
Subject: Re: Exploding Rotors: why you do not drill


> I'm with Fred and Bob on this one, cross-drilled rotors should most
definitely have a symmetrical
> hole layout.
>
> > 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.
>
> these are how they should be done... the rough approximations must be
home-builts, and appear to
> have been done without even the aid of a decent drilling jig...
>
> > 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 ;-)
>
> nope, not a factory hack... these are apparently a Porsche caliper, but
the rotor has once again
> been post-drilled, by monkey with a drill press (IMO)... I wonder if
they're even square to the
> surface...?
>
> I have to agree with Fred that they are Zimmermann's that have been cross
drilled...
> and I would challenge anyone to find pictures from a reputable site or
brand with discs which have
> been drilled in anything other than a symmetrical fashion...
>
> other question is whether the ventilating vanes have been damage in the
course of the drilling...
>
> I would consider cross-drilled rotors myself (don't believe they are
dangerous as a concept) but
> only if I had a good reason to... and they would have to be professionally
done....
>
> JM2C
> Duncan
>