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Drilled Brake Rotors

To: spridgets@autox.team.net
Subject: Drilled Brake Rotors
Date: Thu, 13 Jun 2002 12:06:48 -0500
Fellow Spridgeteers,

Been following the thread on improving brakes, and the thoughts on drilled
rotors in particular.  On the Porsche 944 List, they consider most drilled
rotors to be "eye candy," as they usually crack after hard use, like on the
track.  Seems when they drill the holes, it sets up all sorts of stress
points, and thus helps form the cracks.  The "drilled" rotors that come from
the Porsche factory for the new cars are not drilled at all, but are
actually cast with the holes in place, and thus don't have the stress points
(mega $$$, and not available for older Porsches anyway).  I believe the
original idea for "drilled" rotors was in the 917s back in the early 70's
and the idea was to improve braking in the wet, to get rid of the thin layer
of water vapor that gets between the disks and the pads when water hits the
hot brakes.  Since those brakes were internally vented, the idea was for the
water vapor layer to get sucked in the holes and out through the internal
vents.  I'm not sure that would work on solid disks that have been drilled,
so the holes on Midget rotors may do nothing positive at all.  Anyway, the
general consensus is that "drilled" rotors are a waste of money and as was
mentioned earlier, the slotted rotors (with groves in the face) do a much
better job of getting rid of that water vapor and don't crack.  Just a data

'74 Midget
'90 944S2 Cab

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