Originally Posted by mlhj83
I will only change the caliper if it:
-uses a common shaped pad
-has a larger friction surface area than OEM
-has taken brake torque, balance and heat into account
I have a lot of practical reasons to not want a BBK that I shan't bore you with, but neither am I looking to upgrade the caliper just for cosmetic purposes. I'm happy with the performance of track pads with the OEM setup and don't need the additional thermal capacity of a BBK as I don't tend to do more than 10-15mins of hard driving each time I go out on track. But I do like the benefits of a properly engineered fixed caliper over a sliding one.
I had an experience with a similar system. I originally had a UUC/Wilwood BBK on my E46 which used a pretty common pad shape and the OE E46 M3 rotor. It was an improvement over stock. The biggest issue (cosmetic mostly) was that the caliper didn't cover the entire rotor disc area. So it left a ring of untouched rotor around the hub as you can see in the pic below. It worked fine. It wasn't pretty and maybe it wore the pads down a little faster.
I think a system utilizing the OEM rotor can work but I'm not sure what improvements you get. Most pads for fixed calipers are more expensive. Just some food for thought.