I changed my rotors a couple of months ago and just want to share with you guys/gals what I found when I took the rotors off. This is only on the back side of the rotors, hence the "surprise". 50% of the surface is rusted.
What could've of caused this. I live in the North East and the last couple of winters we had significant amount of snow. However, my other cars never had this problem. The rears are the same as well.
Here's the comparison of new and old.
Installed