FRAME FOR MOTORCYCLE

PURPOSE:To improve the frame stiffness by aligning to the stiffness of an inverted type front fork with restraining the reduction in a handling angle and the weight increase by forming a down tube with one upper tube of rectangular shape whose section is lengthened back and forth and two lower tubes branched from the upper tube. CONSTITUTION:A down tube 6 is consisted of one upper tube 6a welded to the lower part of a head pipe 2 and a pair of the right and left lower tubes 6b branched to the right and left from the lower part thereof. The tube 6a is formed by a tubular material of a long rectangular section, so the stiffness against the bending moment in the car body front and back directions requested for a motor cycle of the tube 6a can be increased without spreading the tube 6a in the car width direction because the sectional secondary moment in the front and back direction of the tube 6a can be made larger. Even if the stiffness in the front and back direction of the tube 6a is increased the tube 6a constrains its spread in the car width direction, so the interference with a bracket 22 is restrained, a handling angle can be secured, yet the weight increase is contributed for the stiffness improvement and unnecessary weight increase is repressed.