Slotted is the only way besides just a smooth stock surface. (No slots, no drilled holes.)
Just cross drilled rotors IMHO are not the way to go. Your losing swept are and not getting much in the way of cooling from the holes.
Much better is slotted to de-gas, and wipe the pad face clean all the time, so you don't get build up of things you don't want there. (Like sand for example, it turns into glass when you use your brakes hard....)
Cooling wise, spiral fins do pump air, but how much I don't know. (Must be worth it because just about every racing rotor made of metal has them incorporated in some way. Only the CF ones just use holes down the middle, or they are just solid rotors of CF material being clamped by pads made of CF material.)
Ok, then we come to mass. You need some mass when using metal based brake systems. (The ones we can afford.. so let's skip the CF arguments here.) Your brakes do nothing more than convert inertia into heat via friction, and dissapate that heat into air flowing over the mass. The more surface area you have for the air to contact, the faster you can transfer the heat. (The crossdrilled arguement.) Problem is air does not like go sideways through holes that have air being blown over both ends, so the air tends to be stagnant unless you create some form of pressure change on either side of the rotor. (With ducts, or spiral fins or whatever, just change the pressure, and bang! The air flows from high to low always.) Still a minimal thermal transfer of heat compared to the surface area of the rotor face, and venting system on even stock vented rotors.
Ok, back to mass, and one more thing you have to consider. Swept area. This is the actual area the pad has contact with. There are a few ways to enlarge it. Either use taller pads that sweep a tall area, or enlarge the diameter of the rotor, and use tall pads.. Here's something funny. The bigger pads do not actually create more stopping force than smaller pads under the same pressure. But the larger pads do last longer under the same conditions, on the same cars. I'm not sure I belive it, but it's what I've been told, and read more than a few times in a few places related to brake systems.
Leverage is also another factor on brakes. By moving your stock calipers out to a new distance from the hub center line, you increase the tourqe of that system. This is another reason larger brake rotors work better. Not only have they increased the mass and swept area, they also improved the tourqe effect of your brakes. (Same pressure results in more brake effect.) Just like you can put more tourqe on the same nut with a cheater bar v/s just straining on the wrench by itself.
There are tons of theories about pad size, piston arrangement to improve pad wear and all kinds of stuff we don't have time to cover, and I'm bored to write about.
The fact is the stock brakes are OK for the stock car. If your making 400hp, you really need to upgrade your brakes. Al in AZ makes a very nice kit for a great price for the front brake upgrade. And it should fit most 17" wheels, a major bonus for most people.
If you want even larger brakes, pull out your wallet and pony up the money, but then enjoy awesome brakes that will slow down your Supracar with confidence at any speed. Figure about 4k to get here. Do you really need this? Only if you need to slow down from really high speeds more than a few times in a 10 min period. (I'm crazy enough to have found this out first hand, and yes, even these brakes fade, but I have yet to find out where they stop working.. and that's about 5 stops from 140mph in 5 miles... then the stock brakes are toast, and these are just getting warm..
)
Fronts. Wilwood GNIII six piston calipers, 14x1.38" slotted rotors.
Rears. Wilwood Forged Billet Dynalite four piston calipers, 14x1.25" slotted rotors with custom steel hats with stock parking brakes inside them
As far as I know, there are only 3 sets of these in the world. Mine and two guys in Europe/Russia. (The rear brakes that is.) The fronts are slightly more common, but not much more as many people go 13" rotor to fit smaller wheels. Speaking of wheels, I really like the SSR Comps. They are pretty dang light, and the quality is impressive, but the Goodyear tires are awesome! I'll buy these again evertime till something better comes along.
