Head stems connect to the fork steerer tube on one end, with the handlebar attaching to the front of the bicycle head stem.
Threadless head stems clamp onto the outside of the steerer and have a 28.6mm ( 1 1/8") diameter. At the other end the standard handlebar diameter is 25.4mm (1") with oversize bars being 31.8mm. Some road bars can be 26.0 - these are Italian or from manufacturers who are emulating the high end Italian brands.
Quill stems (for bicycles with threaded headsets) fit inside the steerer of the fork, and use an expander/wedgeto attach to the steerer. The stem diameter must match the inside diameter of the steerer, which is usually 1/8" smaller than the nominal headset size. Thus the standard quill stem diameter is 22.2mm (7/8"), whilst the standard handlebar fitting is 25.4mm. Quill stems are available for 26.0mm bars. |
