Originally Posted by
akcapbikeforums
Does anyone have pics or diagrams that would illustrate the difference between threadless and quill?
http://www.sheldonbrown.com/gloss_ha-i.html#headset
Keep in mind, it's really the fork steerer tube that's threaded or not. That determines whether you use a quill stem that goes down into the steerer and has the headset threaded onto the top of the steerer tube, or a threadless steerer that has the stem clamped to the top portion of the steerer tube. With threadless, a star spangled nut (installed inside the threadless steerer tube) is necessary for the top cap bolt on the headset to screw into, which preloads the headset bearings.