"I have not idea about the structural analysis in this case." There's your problem. The chainstays are there for Good Reasons. http://www.mece.ualberta.ca/tuto

"I have not idea about the structural analysis in this case." There's your problem. The chainstays are there for Good Reasons. http://www.mece.ualberta.ca/tutorials/ansys/BT/Bike/Bike.html http://www.mece.ualberta.ca/tutorials/ansys/BT/Bike/Bike.htm... If you take them out, now most forces on the bike effect one point in the frame, right beneath the saddle. Making the frame stronger requires more material (=weight) or better material (=price), whereas a rhombus of two triangles solves the problem efficiently. In other words, you are proposing a problem to which the current bike design is the solution.