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 just "eye candy," as they usually crack after hard use, like
track use. 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 newer cars are not drilled at all, but are
actually cast with the holes in place, and thus no 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. The general
consensus is that "drilled" rotors are a waste of money and the slotted
rotors do a much better job of getting rid of that water vapor and don't
crack. Just a data point.
Bob
'74 Midget
'90 944S2 Cab
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