the slots should point in the direction of rotation for cooling.

 

It's not really the surface slots that matter as for direction.

On some high performance rotors, the interior veins are curved to improve air flow. That is where rotation direction matters.

Most basic rotors have straight veins and it matters not which side you put them on.

If they are marked L & R, they prob have curved.

 

Brando is absolutely correct. It doesn't matter which way slots face. Look at these Wilwood slotted rotors. The slots go both ways. So then which way does the rotor go on?

Mentioned in the previous post, if your rotors are marked L and R, then they are probably directional. If you look at the attached picture of the rotor, there is a cut away of the internal vane structure. See how the vanes are directional? You want it such that when the rotor rotates, the air is moving from the center of the rotor to the outside edge, not the other way around. Intuitively, you should be able to figure it out from there.

 

Here's and assortment:
http://s122.photobucket.com/albums/o269/ToddTCE/Rotors/

 

straight off stop tech's web page they are installed correctly.

 

firefox is absolutely correct. it does not matter what direction the slots are facing. different companies slot the rotors in different directions. however, the directional rotors are directional because of the internal veining and should be labelled for which ever side they belong.