Just replaced front rotors and pads on my 2001 Civic LX. Bought slotted and drilled rotors because they were $10 more a side and figured it wouldn't hurt.

Thinking back, they were labelled for left and right sides, but I didn't even look to see. It's been a week. Should I bother switching them at this point?

 

It won't really matter too much. They're still going to heat cycle and fatigue faster, and wear through your pads quicker.

 

Well...you spent the extra $20 to buy them in a certain configuration.

Is it worth $20 of your time to switch them so they work properly? They're designed to move air in a certain way. There really shouldn't be some danger from having them backwards.

It would be kind of like buying a desk fan to cool yourself off and then asking the internet if its worth the effort to get up and flip the fan switch to rotate the correct direction

 

I have seen varying opinions on which way the rotors should be installed. I always went with the instructions of the manufacturer, but for some reason others seem to think differently. Of course, on the internet, you can find any opinion you want.

 

You nailed it... The correct answer is "whatever the manufacturer says" and anything else is just what you said... an opinion on the internet. If the rotor has directional vanes, then they they absolutely need to be oriented correctly in order to function properly. If the vanes are straight it doesn't matter nearly as much and I've seen slots oriented in either direction, depending on the manufacturer and application.

 

There is one manufacturer who markets what they call "noise cancelling" technology for rotors. Never used it, but from what I understand they cut both rotors the same and when you install them, one angles forward while the other angles backward. This is supposed to cancel the noise, one cancelling out the other. Problem with this is that I have never heard any noise to cancel, and if one direction is better, then the two rotors do not function the same. Sounds like they have a creative marketing plan which allows them to cut the same pattern for all rotors.

 

Dunno if I'd believe that without hard info.

As for slotting, look at the Corvette. It actually has its front rotors, one facing one direction, one the other. From testing I've seen, results when exceeding 500 degrees has varied less than 4 degrees depending on direction of the slots. Remember you're not doing slots to keep the rotors cool.

For the cost, the internal vanes are going to be straight cut.

So in short, its not gonna be huge either way. Some cars like the Aston Martin DB9R angle them "forward" as thats the 'correct' direction, but most other manufactuers do it the other way cause its less likely to make noise and the difference of a few degrees isn't worth the potential noise. With your stock sized brakes, you won't notice one way or the other.