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

ir3333 said
Glad this popped up again.
...has anybody had caliper boot interference with new rotors that come with the hubs and hats machined?
I dug mine out and they are completely machined.

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.

Bob Jasinski said
I do have concerns about removing a third of the hat wall thickness, but since the hat only carries force when braking, is not a friction surface, does not support the wheel only the rotor, has safety been compromised? The failure mode I could envision would be under heavy braking, but I would think the wheel would lock up before the hat cracks. I am not a metallurgist or a machinist, although I did have take some classes in both areas in tech school. Is there a safety concern here? Comments welcome.

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.