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In Reply to: Cross-drilled rotors? posted by 89 is on February 25, 2000 at 12:45:21:
: Only recently did I learn that rotors need to be replaced with every brake job. How much longer do cross-drilled rotors last then OEM rotors?
OEM rotors can last for a hundred thousand
miles if you keep using the right pads (organic
as opposed to metallic). My experience with
cross-drilled rotors is on my old 78 Wabbit
canyon chaser, then later on my 85 Golf GTi
autocross car. Stopping distances were
increased with the drilled rotors, probably
due to the loss of so much of the swept area
(pads can't grip holes). They also wore my
pads a lot faster (cheesegrater effect) and
did little to prevent fade as they were intended
to do (probably cause the pads had to work harder
to overcome the loss of grip due to the holes).
When i swapped the stock rotors back on the
car stopped a lot better immediately (both cars).
I also noticed all the holes had small stress
cracks all around them. Also, they cannot be
turned - they can only be milled on a table type
flywheel grinder. They looked cool, but they
don't work like folks think they do. They also
made a weird swishing noise when stopping.
Now on a car with huge brakes (Porsche or actual
race car) the rotors are so big that they can
afford to lose the material that the holes take
away and still have plenty of swept area for the
pads to grab. But on our cars with already
limited disc area i wouldn't want to take any
of it away. I'm extremely hard on my brakes
(autocross, canyon, and offramps :-) but my
stock rotors are still smooth and straight.
The trick is to use soft organic pads like
Ferodo or Pagid. Metallic pads groove the
rotors and don't provide the grip afforded
by the organics.
Randy Walters
89 325is
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