It’s important to note that this size rotor (355mm) is much bigger than stock, so it’s smarter to move to a bigger wheel, however as shown, it can fit the OEM wheels that come on the 2015 STi as long as the wheel weights are moved so they don’t rub the caliper.
Luckily the ST-40 BBK with its specially sized caliper pistons keeps the same proportioning as stock so it is able to work with OEM rear calipers and still allows optimal braking balance. The rear axel was upgraded with StopTech’s 345x28mm slotted rotors and stainless lines. This helps the rear axle brakes resist fade because of the slots that allow the build-up of hot brake gas to escape from in-between the rotor face and the pad, which helps for fade to be minimized. Rotors that are slotted allow for the least amount of surface area being taken up compared to something like drilling which means more stopping friction! The slots are short, perpendicular to the vane and angled to help preserve the rotor’s strength and use the direction of rotation for maximum performance benefits. To ensure my G-loc pads can be beded-in efficiently the rotors are mill balanced which helps reduce vibration and allows for smoother braking, and also double disk ground which also prevents noise on top of improving the pad bedding process.
When prepping for a track weekend or a competitive race I’m always sure to have my G-loc pads on deck. G-loc Brakes pads are the top choice pads for racers who are into late braking. I pair the pads with the Big Brake Kit from StopTech and although the kit comes with a set of pads, those are saved for driving to and from the track.