Thank you. I was tryin' to prove someone wrong earlier, but had no access to the internet(go figure)..

I knew I was right.. :does happy dance:

 

If I was going to go with either cross-drilled or slotted rotors, I would go with slotted. They have more surface area than a normal rotor and cross-drilled have less than a normal one. But the biggest factor when trying to improve braking ( although not necessarily in hard racing) is trying different brake pads.

 

I have personally seen both slotted and drilled rotors crack at VIR in the same day under pretty mild temps and would never run either due to the fact they crack more easily.

For street driving they are fine but, go to a track and you wont see too many of them because they arent as reliable and plus they cost more to replace.

When talking about race teams keep in mind that they change their rotors after every race if not sooner, so they are not worring too much about warping they simply replace them along with a majoity of other parts on the car. If you watch a Rally you can see them changing the rotors and pads at the end of the stages.

If you are paying out of pocket for them you want something that will last you as long as possible. Thats why I run POS plain rotors with race pads for the track and I always bleed my brakes and replace with ATE the day I leave and I have never had any issues. The only time I glazed and warpped my rotors was with POS Hawk pads. No problems with my Carbotechs.

 

I am confused, how does a slotted rotor have more surface area than a blank rotor?

 

if you cut a section through a standard disk, you would have two parallel lines representing the outer and inner faces of the rotor.
for a slotted rotor, the lines would be interrupted by grooves representing the slots. if you measure the distance across a straight line versus one that jogs in and out - even once - you would see that the straight line (shortest distance between two points) has less length (corresponding to area when converted to three dimensions) than the line that jogs in and out.

 

ive read countless articles on this shit.

99% of people should use a high quality blank rotor. Drilled is worthless, except if you want your rotors to crack faster. Slotted is only good in high heat situations with very aggressive pads, thats why alot of race cars use them.

 

Carbon. One of the only materials with a coeff of friction that increases with temp instead of decreases.
In that case, cross drilling weakens the rotors usually because carbon doesn't behave like metal because it's a bonded fiber matrix. The venting does the same damage but it doesn't matter as much because the direction of force is different.

I almost forgot, one of the big reasons that you don't see anything on the face of the carbon/carbon rotors is so that the temperatures can be kept high enough to keep them effecient. Totally backwards of what you want with a metal rotor.

 

The pad contact area is less with slotted, even though the surface area is more. That extra (third) dimension doesn't count in the least bit for braking because it isn't used for a contact surface. In fact, there is less contact surface because you've still removed material from the contact plane. You can't add area to a plane by removing area from that plane.

You guys also need to realize that there is a lot more to rotors cracking than if just if they are drilled, etc. The otherall thermal mass of the rotors can be very different depending on how thick they are, how much physical metal is used, and other things like how fast they can transfer heat from one area to another or how fast the heat can be removed through venting, etc. Then you run into vent design like number of vanes, width, thickness of vane webs, etc.
The only way to make a blanket statement about cracking, warping, etc., is with the same rotors, only differing by the cutouts (holes, radial slots, J slots, etc.) If you have a skinny little rotor that's cross drilled, and then go to a vented rotor that's cross drilled, they're going to be different.
There are a lot of very successful drilled designs out there, and I'll bet that if you find a racing class that uses metal (i.e. NOT F1) rotors, and you see them using blank discs, they are doing so because they are limited by class rules to using a max size rotor so they'd rather have the extra surface area (from not having holes).
It really depends on whether you need the extra area or the advantage of holes/slots.

 

I actually had an article were Porsche admitted that there cross-drilled rotors were for looks only. I had it because I would argue to death with ppl on Honda-tech how they don’t have any real positive purpose and they would come back with "Well why does exotics use them". I deleted it though

 

I agree, cross drilled on street cars is pointless..