-Bikes must be properly balanced on bike racks. The support straps must not be deformed and well balanced. Use this crossbar to solve the problem caused by particular bicycle frames. It is essential for bicycles, especially ladies', and increasingly necessary for modern mountain bikes. This bar has hooks on both arms to connect the straps to bike racks. It is attached between the seat and the handlebars by a telescopic arm 400mm to 800mm in length.