Scalloped Rotors?

[Damn True]

When it comes to rotors, racers are constantly searching for the ultimate balance between the lowest weight and the ability to effectively manage heat. Decreased rotating weight in the drive line provides quicker deceleration under braking and quicker acceleration out of the corners. Lower weight also benefits handling with improved spring and shock control over the unsprung suspension mass. Wilwood's
ULD - 32 drilled and ULS - 32 scalloped iron rotors provide two highly effective lightweight options for sprints, late models, modifieds, and other competition applications that race in low to medium temperature ranges.

View technical drawing

ULS - 32 Series Scalloped Rotors feature a fully machined scallop configuration that provides the highest degree of weight reduction on a vented straight vane iron rotor. Scallop machining will remove as much as three pounds, or nearly 33% of the rotor mass. The vented castings provide increased cooling capacity over machined steel plate rotors, with improved structural durability over drilled rotor designs


That does not sound to me like the description of a part suited for an auto-x or open track environment. With less material (33%) they would be less able to deal with sustained high heat cycles. Again, why would you want to give up over 30% of the swept area?