Welcome,
small cracks are very common between the holes after a few more rigorous heat cycles from spirited driving. The concensus from even the track folks is that they are nothing to worry about as long as the cracks are not very deep and do not connect the holes. The beveled/counter-sunk casting hole pattern is meant to relieve some stress and help stop the cracks but they are just a fact of life using drilled rotors on a performance sports car. As long as the cracks do not connect the holes and there is no blueing/discoloration of the rotors, then they are probably good to go and have not been over-stressed.
Are you in the PCA Santa Barbara Region? My Dad was president in 1992 and remembers someone by your name. I am going to school in San Luis Obispo at Cal Poly. Are you nearby?
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1971 911S, 2.7RS spec MFI engine, suspension mods, lightened
Suspension by Rebel Racing, Serviced by TLG Auto, Brakes by PMB Performance
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