Marked_Man
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Drilled rotors evolved on the track, where companies like Ferrari pioneered the technology. The purpose of the holes is to increase airflow around the hottest part of the rotor, thus cooling the rotor faster. When designing these brakes, the engineers carefully measured surface area, pad area, coefficients of friction, the heat dissipation rates of the friction materials and metal used in the rotors. The materials selected, and the machining processes used were also very specific, to ensure the maximum stopping power, greatest durability, and lightest weights. Everything is put through "worst case scenario" testing on the track to ensure that after 100 or 200 full on brakes, the rotors don't start to anneal or become brittle and develop micro-fractures that could turn into cracks during a race.
Many of the cross drilled/slotted factory replacement rotors you see for sale in stores and on the internet/EBay are just ordinary rotors that have been drilled or machined, and then plated for appearance. There is nothing special about them to make them "race worthy." In fact, many of them will start to develop micro-fractures after a short period of normal street use. As the edges around the holes in the rotors become more and more deformed from these cracks, the brake pads wear more. It's important when upgrading to drilled or slotted rotors to go with a brand name brake part manufacturer.
The other issue is stopping power.
There is a lot of controversy surrounding the trade-off between heat dissipation and surface area (i.e. stopping power.) The more surface area you have rubbing against the brake pad, the more friction, and hence the faster you can stop, so it would seem intuitive to not remove metal by slotting or drilling holes. But more friction = more heat, which causes the brakes to fade due to brake pad degradation, gassing between the pad & rotor, and brake fluid vaporization, so holes/slots help to combat all of these problems.
In most cases a stock vehicle is probably better off with stock rotors, upgraded calipers, carbon fiber pads & hi-temp brake fluid UNLESS the drilled rotor was specifically engineered for the vehicle application. For daily, non-performance driving, normal rotors will give you more pad life and less noise. (Also, it should be noted that full-on braking (i.e. slamming on the brakes) will engage the ABS, which causes the caliper to pulse, which can actually induce cracking in crossdrilled rotors. Race cars typically do not have ABS.)
I found this on another forum and thought I'd share it with everybody.
Many of the cross drilled/slotted factory replacement rotors you see for sale in stores and on the internet/EBay are just ordinary rotors that have been drilled or machined, and then plated for appearance. There is nothing special about them to make them "race worthy." In fact, many of them will start to develop micro-fractures after a short period of normal street use. As the edges around the holes in the rotors become more and more deformed from these cracks, the brake pads wear more. It's important when upgrading to drilled or slotted rotors to go with a brand name brake part manufacturer.
The other issue is stopping power.
There is a lot of controversy surrounding the trade-off between heat dissipation and surface area (i.e. stopping power.) The more surface area you have rubbing against the brake pad, the more friction, and hence the faster you can stop, so it would seem intuitive to not remove metal by slotting or drilling holes. But more friction = more heat, which causes the brakes to fade due to brake pad degradation, gassing between the pad & rotor, and brake fluid vaporization, so holes/slots help to combat all of these problems.
In most cases a stock vehicle is probably better off with stock rotors, upgraded calipers, carbon fiber pads & hi-temp brake fluid UNLESS the drilled rotor was specifically engineered for the vehicle application. For daily, non-performance driving, normal rotors will give you more pad life and less noise. (Also, it should be noted that full-on braking (i.e. slamming on the brakes) will engage the ABS, which causes the caliper to pulse, which can actually induce cracking in crossdrilled rotors. Race cars typically do not have ABS.)
I found this on another forum and thought I'd share it with everybody.