Do I need threaded or Threadless?
In a threadless system the fork’s steerer tube will slide through the headtube of your bike and the stem will clamp on to the portion of the steerer tube that rises above the headset. In all threaded systems the fork’s steerer tube goes into the headtube but does not pass through the top of your headset. In this system the stem (somewhat “L” shaped) inserts directly into the headset and fork’s steerer tube. Most new bikes are already threadless, so the only concern you have is the diameter of the steer tube (1″ , 1 1/8″, 1 1/4″, 1 1/2″- inch). You can measure this by loosening and removing your stem from the fork , and measuring the outer diameter of the steerer directly. Threadless forks need to use a threadless headset, and stem. Threaded forks use a threaded headset and stem with a quill.
