Rotors available (for now) for K-H disc brake cars

That's too bad. I was assuming that this was some company's answer to the casting issue which goes back at least two decades now. The problem seems to be there is only one factory casting these things. Then the different brands buy them and finish (or not) them to various quality levels.

I hate to comment on safety stuff and understand why you have some concerns, but your reasoning seems sound. The heat will be concentrated in the disc. I have temperature sensative paint on the rotors and they've never got excessively hot. I'd be more concened with drilled rotors cracking than what you've done. Contacting the caliper, or even dust boot is just unacceptable. Note that the orignals I have did not have machined hats but were ballanced with weights in the cooling fins. So that's what they cared about! Balance. Probably faster and cheaper than machining the hats which I expect does about the same for balance.

If you are doing track days at Willow Springs, the first thing to get too hot will be the linings. You can talk with Tim and Steve about what you can get away with first times out there. I'd think Porterfield R4S would be sufficient until you get some experience, but they know the track and these cars. So does junkyardhero - and I think he had 4 piston K-H in his early A.

Mattax, Thanks for the thoughtful response. You make a good case about the possibility of drilled rotors being more vulnerable to failure than a solid rotor that's had the hat slimmed down. I have no plans on racing this car, but do plan on spirited driving on twisty roads up Mt Diablo and in the wine country. If you have any pictures of your original rotors I'd love to see them. You mentioned the original hat was rough cast (not machined), but how was the original hat shaped; cone, cylindrical, or stepped?