Another problem with cross drilled rotors is the potential for cracking around the holes. The holes become a stress point in the cast iron that can more readily allow cracks to form in the rotor surface. This requires that you pay close attention to the rotor surface for signs of cracking. Some small cracks, known as "surface checking" are acceptable, but anything that resembles a crack would be a reason to replace that rotor. When looking at slotted rotors keep in mind that the slots should not be milled off of the edge of the rotor. This is a great place for cracks to form, and they will. The slot should be ball milled in the rotor face and originate and terminate on the surface of the rotor without exiting the rotors edge. The goal is to eliminate sharp edges that cause stress risers on the rotor surface. This will reduce the possibility of cracking. If you see slotted rotors with slots that are milled off the edge of the rotor, shop for another brand. Slots that are not cut through the edge of the rotor are a good sign that the manufacturer of that rotor knows what they are doing. This is a good indicator of parts made by a brake company and not a machine shop that happens to drill and slot rotors.
Many years ago, when I ordered my first brake kit from Baer Racing, they told me that drilled rotors would typically last 20% less than an equivalent solid rotor. This was why they always recommended solid rotors for extreme use. Baer has changed their stance on this since discovering there was a large amount of money to be made selling "Eradispeeds" (they are very pretty brake rotors). This change in their marketing strategy has caused me to feel that they have gone from "supporting the racing community" to "making maximum money". And, I guess I can't blame them.....
If you are truly looking for upgraded braking performance for your car. I suggest, as a first upgrade, that you leave the stock size rotors and upgrade the pads. Try a set of Hawk HPS pads or something from Larry at Carbotech Engineering (
www.carbotecheng.com). You'll think you put "big brakes" on all 4 corners (compared to stock).
If you must go bigger, look at any of the various brake upgrades available from many major manufacturers. Brembo, Baer, and many others will have what you need, if you need to upgrade. There are larger kits and they increase in both cost and braking ability. Only your needs and your budget are the limit.
Tires:
I'd also like to take a moment to address the impact that tires have on braking performance.
While it is true that the tires have the "last word" with the pavement when it comes to how the car accelerates, turns, and brakes. There are a few things that tires can and can't do. While it is true that a car on wide, sticky tires should and will out brake the same car on thin, non-grippy tires (all other things being equal). And, while tires are extremely important. They become less important on the 5th or 8th stop or the 3rd lap of a road course. By then the brakes (depending on rotor size, cooling, pads, etc) may be so hot that they can't lock up the skinny little tires, much less the wide, grippy ones. This is where upgrading the brakes pays dividends. This is not meant to minimize the tires role in braking performance. Simply, you must remember to weigh the tires limits against the brake systems limits. You are working with a "package" and changes in one can impact the other. So, while tires will be the limit on the first few stops, they will play a less important role as the brake system temperatures increase. Remember, just because you can lock up the tires on the first stop does not mean that you can't benefit from brake system upgrades.
Class dismissed.
Have fun!
The abbreviated version:
For those who want the short version.
Cross drilled/slotted rotors will not slow your car down any better than stock rotors. They are built to look pretty in the driveway. Iron has a very similar coefficient of friction and it is all about the same. A rotor only has so much metal in it. Metal absorbs heat, metal with holes in it, is lighter than metal without. This will allow it to absorb less heat. So, you will not see any miracles from a set of cross drilled/slotted rotors. Catchy names, shiny parts, great marketing, but they are still "just rotors". Pads...the pads will make a difference (and for much less money). Rotors are still a wear item, and for the money they are asking, I'd hate to run aggressive pads that chew up rotors on slotted, drilled or Eradispeed rotors. However, those same upgraded pads will stop your car and very well. So, I'd buy $60 rotors and $100 pads, instead of $20 pads and $800 rotors. You'll be happier with the result.
Be safe!