Originally Posted by WRX boarder
BBKs adding unsprun weight at the wheels, or only upgrading front breaks upsetting the bias
While it's true the general rule is to run the smallest brakes one can get away with and the smallest wheels that can fit over them, there is a point where the benefit in the ability to deal with heat and provide consistent braking performance after repeated hard use from using larger brakes outweighs the benefit of reduced unsprung weight.
As for the bias issue, there is some wiggle room in that respect of how much the bias is really affected. It's usually not necessary to replace the master cylinder or introduce a brake bias adjuster if the big brake kit was properly engineered to work with the existing components. In respect to OEM WRX twin piston front brakes and theOEM four piston brakes, this really not a problem at all as the four piston equipped WRXs used the same master cylinder.