Forgive my usual ignorance but I dont have both sets of parts, stock and SA
caliper/discs staring me in the face.

If it is the case that the pistons are the same, the pads/swept area is the
same, is the only "bigness" to the SA brake system the vented rotor? There
must be more to it, if the brake disc doesnt have a 0.5" larger radius, why
does one need 15" wheels?

Robert
90 MV