Quote Originally Posted by 9large View Post
That is relatively true for rotors with channels/slots or holes drilled post-fabrication. The cracks typically form where there is less structural integrity - from the edges of the slot or hole. Your analogy would also be more correct if you had to snap the pencil by standing on it, not exerting a directed force. The slots are used to channel hot gases (and even water) from the surface of the rotor, not to accommodate rotor expansion.
You'd hope that all channels/slots are in the cast and not post-fabrication! I would hope it's illegal to do so otherwise (although I hear of people machining the inner surface of their rims to increase offset... and also some drilling other studs in rotors/wheels to change stud pattern.. scary).

For reference, these rotors were only 1 track day old or so before they cracked (pic stolen off Vyet's old forgotten blog )... which also confirms that it's not a distribution of force issue either (At one stage people were saying that possibly the 1 piston caliper was not distributing the pad pressure evenly on both sides, but even with a 4 pot it still happens)

The outer edge to a very small degree would act as a cantilever though as I don't think the force exerted on the "pencil" in this instance is 100% even. But I get what you're saying? And yes I believe slots also help with the deglazing of pads.

Quote Originally Posted by bennjamin View Post
Just another point

S2k Shares the same rotors and pads as ep3s , Dc5rs amongst a few - never heard of these cars having stock rotors crack at any degree ?!
I don't understand either, I'm not involved in other Honda communities so I'm not sure why it's an issue with just track S2000s (never seen it happen on a daily driven S2000)? I don't know if being RWD has anything to do with it as that's really the only difference? Or perhaps, the front hubs are slightly smaller and that plays into it somehow? I dunno - just throwing guesses now.
Locally, I know S2000 people seem to crack rotors faster if they're using R-spec tyres. And in the states, I don't know how much more popular the S2000 is over other Hondas for track use, which may explain why there's more notable cases?

Again this isn't to scare away people from using the stock setup. I know plenty of people on the stock setup with plain (myself included) and even slotted faced rotors tracking just fine.
I'd be curious to find out what the OP went for in the end?