The utility model discloses a novel main cone assembly, including the initiative taper gear, flange, flange lock nut, bearing frame, guide bearing, oil blanket assembly and two tapered roller bearing, two tapered roller bearing's outer lane is all blocked and is arranged in the bearing frame and two back -to -back arranging of tapered roller bearing, and two equal suits of tapered roller bearing inner circle are on the initiative taper gear's axle journal, and the relative terminal surface of inner circle is closely laminated. The utility model discloses a mode that adopts back -to -back setting is held to the initiative axis of cone, and the relative terminal surface of bearing inner race closely laminates, makes main cone bearing pretightning force exempt from to transfer, has changed traditional adjustment mode, has avoided the assembly part to relapse the dismouting in assembling process, has improved product quality.