[Chaplain]

Some put larger rotors on the back because they want rotor hats that incorporate internal parking brake like those offered by Wilwood and still use the classic 15" wheel size. To accomplish this you need the 12.19" rotors. You can fit these inside a 15" wheel because the offset moves the disc away from the hub of the wheel to where the diameter is greater. The problem with the front is that you can only have so much offset because you have balljoints to deal with. Or if you have too much backspacing, it will look like a front wheel drive car. You can make up the difference in rotor size by going to larger calipers in the front with larger pistons and using a proportioning valve. This is a simplified explanation. At the end of the day someone would really have to look hard to detect a 1" difference in rotor diameter.