Since brake torque is a product of total piston area and rotor diameter, I would assume that going to a BBK would increase brake torque over the equivalent stock application. If StopTech says you can use their ST40 front caliper or their ST60 front caliper with the stock rears and brake bias is not affected, they must be varying the individual piston sizes of the ST40 4–piston setup vs. the ST60 6-piston setup to maintain the same overall piston area as the OEM SINGLE piston.
I know StopTech prides themselves on their "balanced brake upgrades," so varying piston sizes must be the answer. Otherwise, an ST40 front/OEM rear or ST60 front/OEM rear would have a different front-rear bias compared to my ST60 front/ST40 rear setup. Is it possible that with the ST60f/ST40r setup they actually allow higher brake torque at each axle over OEM, but front and rear torque is increased to the same degree, so the overall front-rear bias stays the same as OEM?
And what about the rotor diameter part of the equation? The 380mm rotors used with the ST60 front calipers are larger than OEM, so the brake torque should also be increased over OEM, unless they decrease the total piston area vs. OEM to compensate--3 StopTech pistons on one side of the rotor having LESS total area than a single OEM piston--but why would they do this? Are multiple pistons only for providing more uniform pressure/contact of the pads on the rotors vs. a single piston?
I'm probably just reiterating the original post, but I'm trying to work it through in my head...