Good Q ... I recently upgraded my rear brakes (SL600 calipers w/Balo 300mm drilled/slotted rotors). The rotors I purchased did have specific sweep patterns that could be installed sweeping with the direction of travel, ala StopTech, or away from the direction of travel, ala Porsche.

Based on Porsche front and rear rotors that I have seen (and I've seen soooo many lately at the weekly Crystal Cove GTG in Newport Beach, CA) that have cross drilled patterns, have the hole paterns sweeping away from the direction of travel. Again, this appears to be true, front/rear and left/right.

I recently stopped by StopTech's Torrance, California facility and asked about this and why they have their rotor patterns sweeping towards the direction of travel (F/R and L/R). They told me that because of the design of the cooling vanes, the holes are drilled in such a pattern as to not drill into the vane.

Now, I recently saw a current model SL55 that had drilled rotors, and one side had a pattern sweeping away from the direction of travel, and the other side was sweeping towards the direction of travel. Hence, one Rotor part number ... not L/R specific.

So, what does all this mean? Apparently, the direction of the pattern does not matter, that is, if the rotor was designed to be L/R compatible. Porsche sweeps away, and StopTech sweeps towards.

Do you wear your watch on your left wrist or your right wrist? Which side tells the time the quickest?

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1992 500E (Daily Driver)
2004 Porsche RUF 955 Dakara 550