I picked the rear tire and caliper assembly used online, noted as a 99' When i slid original rear rotor into the caliper assembly, the rotor didn't fit into the caliper fully and i was unable to slide the rear axel through the swing arm tire assembly. i replaced the rotor with a Tusk Stainless Steel Brake Rotor, Rear - 1999 Yamaha YZ400F . Without the rotor, everything will fit together. Does anyone know for a fact if a 98 rotor is smaller then the 99 rotor? I don't wanna throw more $ out on something that might be the same. Thanx.