2006 Honda TRX680 Rincon Factory Service Manual, Page 420Get this manual
BRAKE SYSTEM REAR BRAKE DISC INSPECTION Visually inspect the disc for damage or cracksMeasure the brake disc thickness at several pointsSERVICE LIMIT: mm (0.2 in) Replace the brake disc if the smallest measurement is less than the service limit
Check the brake disc for warpageSERVICE LIMIT: 0.5 mm (0.02 in) Replace the brake disc if the warpage exceeds the service limit