no sorry, slotted was made to get the the pad dust away from the sufface and cross drilled was made to to disapate heat.

 

Not sure where you get your information, but that is wrong.

This is alot of reading, but if you think that cross drilling rotors is a good idea, I suggest you read this.

The friction between the pad and rotor is what causes you to stop. This friction converts your forward energy into heat (remember Einstein: Energy is neither created nor destroyed, it is converted). Now that heat is a bad thing. Yes it is bad for the rotors but it is a lot worse for the pads. A warped rotor will still stop the car - it will just feel like crap. Overheated pads however WILL NOT stop the car. It is here where the rotors secondary responsibility comes in. Its job now is to DISSIPATE the heat away from the pads and DISPERSE it through itself. Notice that DISSIPATE and DISPERSE are interchangeable? Once the heat is removed from the pad/surface area it is then removed.

Now let's look at why cross-drilling is a bad idea.

First - as we have already established, cross-drilling was never done to aid in cooling. Its purpose was to remove the worn away pad material so that the surfaces remained clean. As we all know this doesn't have much of a purpose nowadays.

In terms of cooling: Yes, cross-drilling does create more areas for air to go through. Let's look at how this affects everything. The drilling of the rotor removes material from the unit. This removal means less surface area for generating surface friction as well as less material to accept the dissipated heat that was generated by the friction. If it takes longer for the rotor to get rid of the heat it is ok. This means that the rotor needs to have as much surface as possible to generate as much friction as possible and it needs to dissipate the resulting heat AWAY from the pads as quick as possible so they continue to work. In both cases cross-drilling does nothing to help the cause.

Why are they garbage?

- Less usable surface area for generating friction
- Less material to DISSIPATE the heat away from the pads
- Less reliable and they are a safety risk because of fatigue and stress resulting from the reduced material

And that's that.

 

i am still not convinced. i do agree that the cross drilled rotors do have less surface area (which has less stopping power) and are far more likely to warp/crack under presure
(the cheaper ones), but how would you explain that nearly all high preformance cars such as porsche and ferraris solely use these? i believe that they have far more r&d in this peticular area. if you can provide a valid point of why they use these then i will be fully convinced and will change my opinion

 

What are you not convinced on? Less material? Friction? Dissipation? You already said yourself that less area = less stopping power correct?

I am not sure I know the answer to the Porsche or Ferrari question. My guess and it's just that, a guess, is that it lies somewhere in the metallurgy of the materials they use. Perhaps they are heat treated or cryo-treated or utilize a different casting process to manufacturer them? They are still prone to failures as with any other x-drilled application. Why Porsche has decided to use them is beyond me.

In any event I can tell you that the pieces installed on the GT2 are significantly different than the stock blanks that are drilled, re-badged and sold to kids as "performance" items.

 

alot of them are now using carbon fiber or carbon ceramic. they use them because they last,are better at braking, and are lightweight

and i agree in part with both of you. cheap crappy CD rotors are junk and eventually crack/warp but again he's right how do you explain the top end manufacturers who use them like brembo, stop tech, baer,etc etc etc

 

Even baer knows that Cross Drilling is jsut for the bling bling look. Check it out.

http://www.baer.com/technical/faq/index.php