Originally Posted by MotorTrend BRZ TS First Drive

... Fans of the tuner scene will immediately notice the issue: Linking the top of the tS’ front suspension towers is what appears to be a standard strut tower bar, except that instead of one rigid member spanning the engine bay there are two solid shafts connected by a spherical bearing hidden under a protective sleeve. When not bolted to the vehicle, this brace flops around in a most un-brace-like fashion.


Under the car, it gets even weirder. Just behind the engine, two “flexible draw stiffeners” solidly connect both sides of the front crossmember to the body. Or maybe semi-solidly is more accurate because while these draw stiffeners resemble rigid tie rods, they actually telescope a bit under load.


Per Yoshio Hirakawa, the head of STI, the goal of all the newfangled mods is “zero hysteresis driving” — that is, less steering lag and a more linear response from the car. Additional goals include increased high-speed stability and a flatter, smoother, and quieter ride.


How is all of this possible? Some of the applied technology makes sense. Hysteresis is the lag between when the steering wheel of a vehicle is turned and when the vehicle actually begins to turn. Reducing hysteresis has been achieved in sports and race cars by increasing body rigidity via traditional braces and stiffeners. Slop in the chassis from soft springs and rubber bushings can be lessened via harder durometer substitutes, including solid mounts or metal spherical bearings (which the tS also has in the rear suspension linkage). These provide little to no give whatsoever but then introduce other problems, chiefly harsh ride quality, as road vibrations have nowhere to dissipate but up through the seat, steering wheel, and ultimately the driver’s fillings.


This is where the innate flexibility of the BRZ’s chassis and the controlled flexibility of the tS parts seem to work together. STI engineers explained that the flexible strut tower brace and draw stiffeners promote rigidity only in certain directions. The spherical bearing equipped strut tower brace apparently adds structural support across the shock towers for great steering response while also allowing for a bit of vertical movement that is key for maximum tire contact, and a smooth ride. Same goes for the draw stiffeners mounted to the undercarriage; tension within the shafts keeps the wheels running true, even under loads that would cause unbraced wheels to lift or deflect...



http://www.motortrend.com/news/subar...s-first-drive/