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Re: Slotted vs. Drilled Brake Rotors

Gordon Haines asks:
>Does anyone have direct experience with slotted vs. drilled rotors 
>and/or recommendations on such?    

Bob Talbot answers:
>>I plan to slot the next set of front rotors on my car...
>>I know a guy who ran cross-drilled (radially vented) front rotors
>>on a hopped-up VW.  On the track the heat proved to be too much
>>and they cracked.  I have heard of other instances of this occurring,
>>on cars ranging from VW's and BMW's to Audi's and Porsche's.

Gordon,

I think Bob is giving you good advice.  Drilled rotors are lighter 
than slotted rotors, but they are more likely to crack at the 
cross-drilled holes (holes are always stress-raisers -- of course, 
round holes are always better than square holes in this regard). 

Holes or slots help brake performance by reducing the hot gas and brake
dust buildup between the pad and rotor.  The openings provide an escape 
route for all this junk.  This is usually more of an issue on race cars
with large brake pads (more pad surface area to trap stuff) than street
cars with smaller pads.

I've read that slotting the brake pads versus the rotor is a cheaper
and easier alternative for accomplishing the same thing (one vertical
slot and one horizonal slot).  I haven't personally tried slotted 
rotors or put extra slots in my pads.  However, I've noticed many 
brake pads such as Cool Carbon have a vertical slot (Metalmasters for
my car don't have any slots).

  Regards,

  Pete Read
  '88 M5