Why are the front rotors directional? When comparing the rotors the seem symetrical to each other. It would be impossible to tell left from right without the arrows. Why couldn't I use a left in place of a right? The reason I ask is because I have 2 good left rotors and to bad rights. Iv'e got a major case of spring fever and can't find a right side rotor anywhere. Ebay has sets on but they are going for a lot. And some of the sellers didn't even spin them on a lathe or break machine to check for trueness (I don't think "trueness" is a word but you know what I mean)