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Huge amounts of information out there for this one. Drilled rotors are for 1) curing pad outgassing, a problem that hasn't existed since the early '70s, and 2) making the rotor lighter, as is used in some formula car classes and motorcycles, where unsprung rotational weight is bad.
Drilled rotors on modern cars is for that vintage race car look and has NOTHING to do with increasing stopping power/shortening stoping distance. The few higher end manufacturers that do it on their stock vehicles ALSO increase the diameter of their rotors in comparison to the mass of the car in order to make up for the LOSS of rotor mass caused by drilling.
Rotors need to remove heat from the pads generated by friction. The larger surface area the better. The rotor's surface is where the pads contact and generate friction to slow the vehicle down. Since it is this friction that causes the conversion of forward acceleration into deceleration you ideally want as much as possible. The mass absorbs the heat, the rotor, by way of thermal transfer dissipates the heat throughout itself, then the surface area again steps in to radiate the heat to the air. Drilling holes removes friction area (used to generate decellerative forces) reduces mass (which is used to absorb the heat) and structurally weakens the metal (creating, even with chamfers, stress risers where the holes cool off faster than the surrounding material). ALL drilled rotors crack eventually, and under heavy use, they crack faster.
If they helped the car stop faster, it would be from higher speeds and under track use, not street use. The irony is, drilled rotors are crap for track use and ONLY safely used on the street where the rotors are not being stressed ANYHOW.
The plain truth is: if your car can already lock up the tires (or invoke ABS on so-equipped cars), no amount of big braking will stop the car even ONE INCH shorter. Once you are at the limits of your tires' traction, that's it. You might be able to stop fast more OFTEN (due to not overheating), but you can't stop any quicker. In order to do that, you need stickier tires.
The lesson is, get stickier tires to stop faster, and then get better pads to stop fast repeatedly. Leave the drilled rotors for show cars (and that includes Porsche and Ferrari and even the new Corvettes, all of which experience rotor failure on the track when used as supposedly intended).
Slotting can still crack, but they do remove the layer of glaze that can happen to pads that have been overheated, and slots also do a nice job of removing water and dirt from the pad/rotor interface. But again, they can still crack.
Nice pics, cracking is very evident on both slotted and drilled.
Nothing to add beyond what Merc said, other than the best performance solution is good solid rotors, the right pad for your application and good quality brake fluid.
There's a very common misconception that bigger brakes or drilled/slotted brakes will help you stop faster. It's simply not true, the tires determine maximum grip, once you reach that limit, no brakes will help stop you faster, and though, as he says, larger brakes (and bigger/more piston calipers) can enable you to do several of those stops in a row, something that's only important on a track, they will not stop you any faster than OEM brakes, as I don't think I know a single car in production today that can't brake hard enough to either have the ABS kick in or screetch the tires.
Lot of rubbish being spouted on this thread.
Many old myths are being rehashed !!!
1. Grooved rotors, does aid cooling slightly, but makes sure that the dust generated by braking is dispersed better. It can also lead to slightly sharper braking because it stops the pads glazing. It does have a direct benefit on performance.
2. Drilled rotors. The only benefit to having drilled rotors is that it reduces unsprung weight, and on a racecar, that does have an effect on handling and cornering. Any effects on cooling are negligible.
To be totally honest, the benefits all round of having these parts on a standard road car are pretty negligible.
If it's a car which you also drive on track, then it's probably worth it, but be prepared to replace them more frequently than stock.
Buy a new set of stock rotors, and a decent set of pads, (none of your $2.99 Wal-mart special offers) and your brakes will function just as well.
Buy a new set of stock rotors, and a decent set of pads, (none of your $2.99 Wal-mart special offers) and your brakes will function just as well.
Ding, ding, ding!
I will also add that drilled or slotted rotors remove surface contact so by adding them when you don't have a brake fade issue braking performance will decrease.
However, in regards to rotors I must say I do believe in having them cryo-treated. My wife kept warping her rotors (and I know it wasn't due to over-tightening of the lug nuts since I do all the service work and the lug nuts are tightened with a torque wrench.) so I finally added a quality set of blanks that had been cryo-treated. After a year and a half still no vibration.
I have drilled rotors on a 560 (and previously, a Gallardo) and they're a maintenance annoyance because they collect brake dust in the holes. The Gallardo had very dusty brakes and after just a few thousand miles, the rotor holes were mostly filled with brake dust. I liked to keep the car in sparklingly prestine condition and it bothered me to have the holes filled up, so I would use a paper clip to clean all of them. That car was never tracked either.
If you get drilled rotors, get low-dust pads too!
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