2000 Yamaha YFM400FWA(M) Factory Service workshop Manual, Page 268Get this manual
FRONT AND REAR WHEELS
BRAKE DISC INSPECTION 1.Inspect: Brake disc Gallingdamage Replace2.Measure: Brake disc deflection Out of specification Inspect the wheel runoutIf wheel runout is within the limits, replace the brake discBrake disc maximum deflection: 0.15 mm (0.006 in)
Brake disc thickness Out of specification ReplaceBrake disc minimum thickness: mm (0.12 in)