Mean axis of bicycle

A mean axis of bicycle comprising a five-way pipe, an internal pipe, two setting rings, two ball housings, an axle and two ball bearing, and cooperating with a master chain wheel set in practising;

• and the improvements comprising:
• said five-way pipe comprising two conic surfaces at respective inner ends thereof;
• said internal pipe comprising two threads at respective inner ends thereof;
• said setting rings comprising a conic surface formed at an outer end as a spigot corresponding to said conic surfaces of said five-way pipe, and an inner threaded hole from the other end;
• said ball housings comprising a ball track at an inner end, thread surrounding over the outside surface, and a ring seal embedded into said ball housings;
• wherein by threading said ball track end of said ball housing into one end of said internal pipe, one of said ball bearing, said axle and the other said ball bearing are inserted respectively from other side, then the last ball housing is threaded into the internal pipe from the other side so that the ball bearings seat in the ball tracks respectively to form a mean axis assembly;
• then inserting the combined mean axis assembly into the five-way pipe, and turning two setting rings from both sides of the five-way pipe so that the conic surfaces of the setting rings press against the conic surfaces of the five-way pipe tightly fix the mean axis assembly in the five-way pipe;
• making use of the gaps between the inner ends of the setting rings and both ends of the internal pipe, turning the setting rings out and in separately adjust the axle shift left-right to adjust the allowable range.