Swing arm

A swing arm comprising:

• a vehicle-body-side support portion that is supported on a vehicle body side by a first rotary shaft;
• a wheel-side support portion that is supported on a wheel side by a second rotary shaft;
• and
• a pair of arm portions that connect the vehicle-body-side support portion and the wheel-side support portion to each other, wherein
• a cross member that extends in an axial direction of the first rotary shaft is arranged on the pair of arm portions so as to extend between the pair of arm portions, and
• the cross member has a U shape in cross section orthogonal to a longitudinal direction of the cross member thus forming an opening portion that opens so as to face a direction that the pair of arm portions extends,
• wherein the cross member includes:
• an upper wall and a lower wall that project in the direction that the pair of arm portions extends;
• a vertical wall that extends between the upper wall and the lower wall;
• and
• a bent portion that has an edge thereof bent toward the vertical wall is formed on the upper wall and the lower wall,
• wherein the cross member is formed by bending a plate material,
• a flat planar portion is formed on the vertical wall, and
• a mounting portion for mounting a chassis-group member is formed on the planar portion.

A swing arm comprising:

• a vehicle-body-side support portion that is supported on a vehicle body side by a first rotary shaft;
• a wheel-side support portion that is supported on a wheel side by a second rotary shaft;
• and
• a pair of arm portions that connect the vehicle-body-side support portion and the wheel-side support portion to each other, wherein
• a cross member that extends in an axial direction of the first rotary shaft is arranged on the pair of arm portions so as to extend between the pair of arm portions, and
• the cross member has a U shape in cross section orthogonal to a longitudinal direction of the cross member thus forming an opening portion that opens so as to face a direction that the pair of arm portions extends,
• wherein the pair of arm portions is constituted of a front arm portion and a rear arm portion, which are arranged in the longitudinal direction,
• the cross member is constituted of a vehicle-body-side cross member, which is arranged on the vehicle body side, and a wheel-side cross member, which is arranged on the wheel side, and
• a front connection distance between the vehicle-body-side cross member and the wheel-side cross member, which are connected to the front arm portion, is larger than a rear connection distance between the vehicle-body-side cross member and the wheel-side cross member, which are connected to the rear arm portion.