The following information applies to the 2011 Subaru WRX and STi, and comes from the Subaru Factory Service Manual.  16- and 15-inch type refers to the floating pad configuration on the WRX (even though it likely came with 17-inch wheels).

Front Brakes

Front Brake Pad Service Limits

Front Brake Pad Thickness

                       Specification      Wear Limit
16-inch type (WRX)     11mm (0.433in)     1.55mm (0.059in)
17-inch type (STi)     8.9mm (0.35in)     1.2mm (0.047in)

Front Brake Rotor Service Limits

Front Brake Rotor Thickness

                       Specification     Wear Limit        Disc Rotor Diameter     Disc Rotor Runout Limit
16-inch type (WRX)     24mm (0.94in)     22mm (0.87in)     294mm (11.57in)         0.050mm (0.0020in)
17-inch type (STi)     30mm (1.18in)     28mm (1.10in)     326mm (12.83in)         0.075mm (0.0030in)

Front Brake Tightening Torques

                       Support to Housing     Caliper Body
16-inch type (WRX)     80 Nm (59 ft-lb)       27 Nm (19.9 ft-lb)
17-inch type (STi)     NA                     155 Nm (114.3 ft-lb)

Rear Brakes

Rear Brake Pad Service Limits

Rear Brake Pad Thickness

                       Specification      Wear Limit
15-inch type (WRX)     9.0mm (0.354in)     1.5mm (0.059in)
17-inch type (STi)     9.0mm (0.354in)     1.2mm (0.047in)

Rear Brake Rotor Service Limits

Rear Brake Rotor Thickness

                       Specification     Wear Limit        Disc Rotor Diameter     Disc Rotor Runout Limit
15-inch type (WRX)     10mm (0.39in)     8.5mm (0.335in)   286mm (11.26in)         0.050mm (0.0020in)
17-inch type (STi)     20mm (0.79in)     18mm (0.71in)     316mm (12.44in)         0.075mm (0.0030in)

Rear Brake Tightening Torques

                       Brake Hose Bracket     Caliper Body Assembly
15-inch type (WRX)     33 Nm (24.3 ft-lb)     66 Nm (48.7 ft-lb)
17-inch type (STi)     33 Nm (24.3 ft-lb)     65 Nm (47.9 ft-lb)