Abstract: An inexpensive, easy to manufacture security device for bicycles with a telescoping U-shaped shackle which collapses sufficiently to store the lock within the frame of a small frame bicycle and capable of telescoping sufficiently to be effective in having the U-shaped shackle pass through the bicycle wheel, frame and around a stationary object. The ends of the shackle are secured by inserting into two side holes in a tubular lock bar. One end of the shackle possesses a round lateral pocket which passes over a retainer inside the lock bar to prevent removal of the shackle. The other end of the shackle possesses a square notch which engages a key actuated lock core. The shackle can be adjusted for length when secured by the lock bar or with the bar removed.