2009 Polaris Sportsman 850 XP EFI EPS Service Manual, Page 288Get this manual
BRAKES 2Remove mounting bracket, pin assembly and dust boot
Caliper Inspection
1Inspect caliper body for nicks, scratches or wearMeasure bore size and compare to specificationsReplace if damage is evident or if worn beyond service limitUsing hammer and small punch, remove the piston from the caliper body, then remove the square O-rings (see "BRAKE CALIPERExploded View")
= In mmFront Calipers: Caliper Bore I.DStd: 1.192" (30.28 mm) Service Limit: 1.194" (30.33 mm) Rear Calipers: Caliper Bore I.DStd: 1.254" (31.85 mm) Service Limit: 1.256" (31.90 mm) 4Clean the caliper body, piston, and mounting bracket with brake cleaner or denatured alcohol2Inspect piston for nicks, scratches, wear or damageMeasure diameter and replace if damaged or worn beyond service limit