In motorcycle race represented by MotoGP, the motorcycle bank angle in turning state reaches approximately 60 degrees. In such a large bank angle, it is important that response of the motorcycle for the road surface displacement input is relaxed by designing the frame with low stiffness in the side direction to secure the speed on cornering.
On the other hand, strong frame stiffness of longitudinal direction is required with a proper frame displacement to resist large force by the rapid deceleration.
As seen above, regarding stiffness of longitudinal and side direction of the frame of motorcycle, one should be high, and the other should be low.
However, in general, the ratio estimated by stiffness of side direction per that of longitudinal direction is approximately constant with existing frame. This means that if the frame stiffness of side direction is lowered, that of the longitudinal would also be lowered accordingly.
Thus, it is difficult to design the frame of which stiffness of longitudinal direction is strengthened while that of side direction is kept lowered.
An object of this study is the development of the frame with different longitudinal and side stiffness ratio unlike the current longitudinal and side stiffness ratio.
The frame developed from this study is adopted in our MotoGP machine and contributes to secure high speed on cornering.