Heat = Cracks
Just about every form of metallic brake rotor will crack. The reason that it is usually more noticable on drilled rotors is due to the fact that most people who have drilled rotors tend to be a little more spirited with their driving. They also have a tendancy to get their rotors and brakes hotter and then not cool them sufficiently before putting the car in the garage or parking. Many times I have pulled next to a performance car in a parking lot, and could actually feel the heat from tha rotors as I walked past. I have had slotted, drilled, and slotted and drilled rotors on most of my vehicles over the past 15 years and I can say from experience that if they are taken care of, they will outlast and provide better stopping capabilities than plain rotors. The only reasons that the slots or holes are put in the rotors is to allow the gasses to escape from between the rotors and pads under braking pressures. They will also help to dissipate the heat, but it is the design of the fins in between the actual braking surfaces that do the majority of the heat dissipation. Rotors are almost always directional in nature and if you or your friends are experiencing severe cracking of slotted and or drilled rotors, this is the first place to check. As a brake tech for many years, I can tell you that plain rotors usually have more cracking than slotted or drilled rotors, it just usually does not show as well due to the dragging effect of the pads on the rotors. In effect the metal is dragged into the cracks at high temps and the rotors look like they are smooth. Look at them under a magnifying glass and this will become apparent.
If drilled and or slotted rotors are so bad as stated, then why do all of the high performance and exotic cars have them factory installed?? I have never seen a viper or Ferrari without them.
