Yes the Porsche rotors have holes in the castings
but the holes are re-drilled after machining the castings.
Their rotors are cast from a better iron quality than the
average quality for passenger cars, but they still crack
around the drilled holes after some 50 quick laps of
Nurburgring or something similar. Porsche brake parts
are made by Brembo but pads are from Textar (Bosch-ATE)
Cross drilling a brake rotor is difficult to do right and if
the casting quality is bad, they will crack after a few miles.
Cross drilled rotors give a more agressive bite than plain
rotors but almost the same thing can be accomplished with
slotted rotors with reduced risk of cracks.
Thomas
Adam Bradley wrote:
> I was told that Porsche rotors are cast with the holes in place rather than
> drilling the holes later. They are "pseudo-drilled".
>
> At 07:32 PM 6/26/2002 -0400, datsunmike wrote:
> >Supposedly its main pupose is for outgassing of the pads which is no longer
> >true (pads haven't had that problem in almost 30 years) BUT they are also
> >used to dissapate water in wet conditions.
> >
> >Personally I think its another kind of snake oil and just looks better if
> >you like that racy look. However I could be wrong.
> >
> >Grassroots had a long article about brakes and in particular a long
> >discussion about rotors. They said what I feel but maybe what I feel came
> >from their article as well as others.
> >
> >Those drilled rotors are particularly bad unless manufactured by a very
> >reputable company and even then you have to keep your fingers crossed. I
> >have heard of several stories about the rotors cracking under pressure as
> >the holes caused stress risers. Yes, Porsche uses them but those are Porsche
> >parts made under strict guidelines.
> >
> >Mike
> >
> >----- Original Message -----
> >From: "Ed Wilsey" <Kensington_FC@hotmail.com>
> >To: "Stephen McCartney" <sgam@hotmail.com>; <roadster@texoma.net>; "List"
> ><datsun-roadsters@autox.team.net>
> >Sent: Wednesday, June 26, 2002 10:26 AM
> >Subject: Re: Question about front disc brakes
> >
> >
> > > What is the purpose of slotted rotors? Is it for heat dissipation?
> > >
> > > ??//
> > >
> > > ----- Original Message -----
> > > From: Stephen McCartney
> > > Sent: Wednesday, June 26, 2002 3:58 AM
> > > Subject: Re: Question about front disc brakes
> > >
> > >
> > > Even the guys who race here are using a more or less stock setup, except
> > > with slotted rotors (still available here in Australia through DBA). Get
> >more
> > > from the Web. FREE MSN Explorer download : http://explorer.msn.com
> > >
> > > /// datsun-roadsters@autox.team.net mailing list
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> >
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>
> Adam Bradley
> '70 Datsun 1600 Roadster SPL311-28181
> '66 Datsun PL411 sedan PL411-022447
> http://www.picturetrail.com/abend
>
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