Front Disc Rotor: Inspection

Check the front wheel bearing play and axle hub runout before the inspection of disc rotor runout limit. Refer to INSPECTION , Front Axle.
Secure the disc rotor by tightening the five wheel nuts.
Set a dial gauge 10 mm (0.39 in) inward from the disc rotor outer circumference. Rotate the disc rotor to check runout. If the disc rotor runout exceeds the limit, resurface the disc rotor. After grinding, check the thickness of the disc rotor according to the procedure in step 4).

Fig 1: Checking Disc Rotor Runout
Courtesy of SUBARU OF AMERICA, INC.

Disc rotor runout limit: 0.05 mm (0.0020 in)

Set a micrometer 10 mm (0.39 in) inward from the disc rotor outer perimeter, and then measure the disc rotor thickness. If the thickness of disc rotor exceeds the service limit, replace with a new disc rotor.

Fig 2: Identifying Disc Rotor

Courtesy of SUBARU OF AMERICA, INC.

DISC ROTOR SPECIFICATIONS

Standard				Limit	Disc rotor outer diameter
Disc rotor thickness A	mm (in)	16"	24 (0.94)	22 (0.87)	294 (11.57)
Disc rotor thickness A	mm (in)	17"	30 (1.18)	28 (1.10)	316 (12.44)