[Ian]

I agree with curt. you also have to think of radiators as another example of heat transfer. Heat will escape from metal at the edge better than from the middle of the material. Fins on radiators are what make them effective. the more fins or edges you have, the more heat will get transfered. Similarly, the more edges you have on a brake rotor, the faster it will dissipate the heat it absorbs. the holes drilled into the rotor create more edges for the heat to escape and also provides more area for air to pass through, aiding in heat transfer even more.

another common item you can look to for an example would be a heat sink. they dont make them into a solid block, they give them as many edges as they can. why? because heat escapes the parent metal faster through edges where the metal is surrounded by more air.

Drilling a rotor *can* weaken it, that much is true. These *weak* spots are more prone to cracking, but because the rotor will stay cooler than a solid rotor would, less heat builds up and the chance of cracking the rotor is greatly reduced.