Love this post, I want to upgrade to 20" wheels and the rotors look to small on that setup. I definitely will consider doing this if I can upgrade front and rear rotors.
So I started to do some research on realoem as the X3 has the electronic parking brake with the EMF actuator which is limited to a few models (see list here:
https://www.realoem.com/bmw/enUS/par...34216794618%09)
The idea is that the new rear caliper needs to connect seamlessly to the existing connector for the e-brake. the f15 uses the traditional e-brake system found in the E90 with brake shoes inside the rotor, whereas this new system uses an electronic actuator to lock the rotor with the updated mechanism eliminating the need for e-brake shoes.
My concern is I want it to match the F15 rotors 5.0 rotors, so that means M6/M5 (f10/f06/f12) rotors wont work out as they are too expensive for me at this moment. All of the non M rotors seem to be 345x24. The rear rotors on my f25 are currently 328x28. The rotor meets the criteria of increasing surface area however the reduced thickness of the 345x24 causes concern about fitment and stability as I assume I will have to use washers to make up the loss of the 4mm of width.
Or, is that concern not valid as long as I use the matching caliper for the F06? I know I cannot use the existing caliper on the X3.
Thoughts on this anyone?