Exploding Rotors: why you do not drill

Brett Dikeman brett at cloud9.net
Fri Jun 20 22:02:40 EDT 2003

At 6:46 PM -0400 6/20/03, TM wrote:
>If they were Zimmermans, I wouldn't say it is commonplace for
>this to happen- I've had a few friends with Zimmerman drilled
>rotors and they have had no problems.
>There is obvious cracking- why didn't someone catch this during
>trackside tech?

Well, the answer is the club doesn't don't do "trackside" tech.  The
owner is responsible for the vehicle's condition.  I know many PCA
regions, for example, put people through lug nut torque checks.  The
problem is that now you've given your stamp of approval.  What if
your torque wrench isn't working properly, or hasn't been calibrated
recently/properly?  What if you had it set incorrectly, or you used
the wrong torque for that vehicle?(many different makes+models come
to NEQ events, not just Audis!)  You're now in some very hot legal

   The NEQ requires a complete mechanical inspection in advance of the
event by a professional, certified mechanic(what the club calls a
pre-tech).  That's handled by the owner exclusively.  The club then
does an event tech inspection, which is much simpler and is designed
to catch major problems that might have cropped up since the
pre-tech; leaks, suspension coming apart, so on etc.  It's also just
yet another check of the basics.

The car cleared event tech the night before the first day; I signed
off on the car, and I warned the owner about cross-drilled rotors; I
gave the rotors a good eyeball, and they were clean.  The owner
acknowledged the warning after the incident- he seems to feel we
adequately handled the situation, enough to the point that he sought
me out and practically apologized for not heeding my warning and not
keeping a closer eye on the situation- the guy felt guilty, if
anything, for causing a hiccup and endangering others.

It is entirely the owner's responsibility to keep the vehicle in
functioning shape.  Speaking from first-hand experience as a student,
participants are repeatedly reminded, by the materials they're given,
the classroom instruction, and by their instructor- to examine the
car before each run, particularly brake pad and tire condition, since
those are the big wear items.  If you're looking closely enough to
see brake pad condition, you'll see rotor problems.

At 7:01 PM -0400 6/20/03, JShadzi at aol.com wrote:

>I agree, like I've said before, this is a one in a million failure,

While exact probabilities would be difficult to come by, whatever the
failure rate is, it's unacceptable.  Brake rotors should, regardless
of how they are used/abused, fly apart and destroy the entire wheel
assembly and render the entire brake system dead.  Scott J told me
that almost exactly the same thing happened last year at a Gingermann
Raceway event.  He said they were cross-drilled rotors and they
failed in exactly the same manner, causing rather similar damage.

What does that tell me?  That either the product is defective or
being used in the wrong applications/situations- and/or that it is
less reliable/tolerant.  Whatever the reason, it does not matter-
clearly something is wrong.

>  every manufactured product has defects and failures
>, I seriously doubt that this rotor failed simply or only becuase it
>was drilled.

You're right, they were probably overheated- and if they had been
solid rotors, they probably would have warped, but they probably also
wouldn't have failed in such a spectacular manner.  Have you ever
heard of a solid rotor coming apart violently?  I haven't.  I've
heard of plenty of cross-drilled rotors cracking...

"They're fine as long as they don't overheat" is great if you have
adequately sized brakes, cooling ducts, are a good driver who doesn't
overdrive the car, etc.  They should not be billed as street
equipment or an upgrade that will yield additional stopping power-
because they won't.

>   Zimmerman rotors are sold by tens of thousands of auto shops and
>part suppliers across the US not including the World,

...which was exactly my point in mentioning them by name.  They're a
fairly big name in the business...which is possibly why the owner
selected them(or simply they were the most accessible).  The problem
isn't necessarily with the individual manufacturer...

>  I'd think if there was a real problem that you'd hear more about it
>  or that some action would be taken against them.

That theory is pretty well shot down by the various blinking/beeping
fishing lures you can buy through late-night TV ads.  Nevermind
energy crystals, any number of magnetic healing devices, metal
wristbands...as P.T. Barnum said, "a fool and his money are easily
parted."  The automotive world is full of thousands of
useless/dangerous/defective products.  There mere existence, or even
success, does not automatically validate the product.

>Like Taka says, all brake systems need to be checked periodically,
>especially under track driving where stock TT brakes are being very
>taxed and over-exserted.

...which is yet another reason why cross-drilled rotors, which are
known for cracking when overheated and have less thermal mass, had no
business on that car.

"They that give up essential liberty to obtain temporary
safety deserve neither liberty nor safety." - Ben Franklin

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