While doing the back tire I discovered that my rear rotor was at the minimum 4.5mm. I decided to use the one from my parts bike. I got the rotor off and its smaller and not offset from the tire or slotted. The bikes are the same year. Can I use this rotor or should I find another? I doubt if that rotor is not original, parts bike only had 13k miles on it. Also thinking maybe he swapped wheels with a MKI.