The Subaru Impreza WRX STI was already a highly optimized performance machine. Specific chassis tuning. Aluminum front lower L-arms reduce unsprung vehicle weight. Major chassis tuning changes include a lowered ride height and new pillow-ball bushings in front and stiffer bushings for the rear subframe that supports the double-wishbone suspension - these improve camber and toe stiffness.

Both the front and rear suspension systems employ higher-rate springs and thicker front and rear stabilizer bars than the 2010 model: 21 mm vs. 20 mm in front and 19 mm vs. 18 mm in rear. Spring rates have increased by 15.6 percent in front and 53 percent in the rear.

New standard 18-inch aluminum wheels feature high-luster paint and weigh 17.6 lbs. less than the previous standard wheels. The optional 18 x 8.5-in. BBS® forged aluminum-alloy wheels, which further reduce unsprung vehicle weight, are highlighted by silver high-luster paint for 2011.

Exclusive to the Subaru Impreza WRX STI, the Brembo Performance Brake System uses ventilated 4-wheel Super Sport anti-lock (ABS) disc brakes with Electronic Brake-force Distribution (EBD). Super Sport ABS can control the braking forces at each rear wheel independently, which optimizes braking ability during hard cornering to help reduce understeer.