Bicycle

A folding bicycle comprising:

• a frame having a seat tube, a down tube, and a top tube which form a rigid triangle structure, wherein
• the top tube and down tube are connected to a head tube, while
• the seat tube and down tube are connected to a crankshaft bearing housing,
• the top tube and seat tube are joined below a seat of the bicycle,
• the bicycle further has front and back wheels connected with the frame via a front fork and rear fork,
• an inclined strut extends from the top tube to the down tube, the inclined strut being joined to the top tube via a pivot, while a connection of the inclined strut to the down tube is arranged to be opened,
• the down tube comprises two parts detachably attached to each other,
• the top tube is at one end connected to the seat tube via a first pivot joint, a rotation axis of the first pivot joint being at a non-perpendicular angle β with respect to a longitudinal axis of the top tube, as viewed from above the bicycle,
• the rotation axis of the first pivot joint is at a non-perpendicular angle γ with respect to a longitudinal axis of the seat tube as viewed from a front of the bicycle, the angle γ being on a first plane that is parallel to the seat tube, the angle γ being 2 to 9 degrees with respect to a line perpendicular to a second plane that passes through the top tube, the seat tube and the down tube in an unfolded state of the bicycle,
• the top tube is at its other end that is opposite the seat tube connected in a pivoted manner with the head tube at a joint, so that a rotation axis in the joint is perpendicular to the longitudinal axes of both the head tube and top tube, and
• in a folded state of the bicycle, the two parts of the down tube are detached from each other and no longer connected to each other.