Quill stems can be removed without disrupting the headset.Quill stems may offer a slender, smoother appearance compared to the multi-piece, jointed appearance of a threadless stem.To raise or lower a threadless headset beyond predetermined (spacer) increments requires another stem. Quill stems can simply be raised, especially examples with long shafts.Quill stems offer the ability to make fine adjustments to handlebar height.Threadless stems avoid the internal binding or seizing possible with a quill stem's wedge or cone bolt.The threadless stem's centering can be adjusted without disturbing the handlebar height.(Some quill stems also use a single allen wrench.) Threadless stems can be changed with a single allen wrench.Threadless stems allow for the lighter carbon fiber or aluminum alloy steerer tubes, and hence a lighter overall bicycle.Threadless stems offer a simple way to swap, flip, mix, and match stems, which are readily available in various configurations and variations of construction, color, reach, and angle.Special adaptors may allow a threaded fork to receive a threadless stem.Īdjustable threadless stem with a removable face plate. (See: photograph of star nut) Newer model forks, with carbon fiber steerer tubes, use an expander plug instead of a star nut, which once installed serves the same purpose as the star nut, but will not damage carbon fiber forks as a starnut will (by design a star nut digs into the surrounding tube, which, while safe with aluminum, can weaken carbon fiber to the point of failure). The top cap bolts into, and pulls against, the star nut, thereby preloading the headset bearings. With threadless stems, a star nut is driven down into the threadless steerer tube and held in place by two barbed flanges. Threadless stems are commonly available in lengths up to about 130 millimeters (5 inches). Threadless stems feature a modular design where the stem clamps around the outside of the top of the fork steerer tube that protrudes above the headset. Threadless stems, the newer of the two styles, are widely popular and have displaced quill stems as the industry standard on sport bikes. The cone-shaped expander nut is pulled upwards by the bolt causing the sides of the stem to spread and press against the inside of the steerer tube to hold it in place. In the case of an expander nut, the bottom of the stem is cut perpendicular to its length and also has two slits cut parallel to its length. In the case of a wedge-shaped nut, the bottom of the stem is cut diagonally to match the wedge and the bolt pulls the wedge against the stem to expand against the inside of the steerer tube and hold the stem in place. The quill stem fits down into the inside of the top of steerer tube and is held in place by either a wedge-shaped nut and bolt or a cone-shaped expander nut and bolt. The quill stem requires the threaded steerer tube of the fork to extend up through the headset but not protrude beyond it. However, they remain standard on the majority of utility bikes, regardless of price, as well as on less expensive sport bikes and higher-end retro bikes. The older of the two handlebar stem styles, quill types have been largely displaced as the industry standard on sport bikes. Quill stems showing wedge-shaped (on left) and cone-shaped (on right) expander nuts. Unthreaded forks often require less labor to swap than threaded forks. The steerer tubes are then cut to length to fit upon installation. With the advent of threadless stems, manufacturers no longer need to provide a range of threaded forks for a given model all threadless system forks are made with the same length steerer tube (long).
Quill systems predate threadless systems.
Threadless systems use an unthreaded steerer tube, which extends into the stem and may be cut to length as desired in order to accommodate the height of the headset, head tube, stem and any spacers used to adjust the handlebar height. Quill stems require a steerer tube of the same length as the headset and head tube combined and thus must be matched to the specific bicycle model.
Threadless: the stem clamps around the steerer tube, which is not threaded and extends above the headset.Īlthough stems are commonly referred to as being of either the quill or threaded type, the thread in question is the one on the fork steerer tube.Quill: the stem inserts into the steerer tube, which is threaded and does not extend above the headset.Sometimes called a goose neck, a stem's design belongs to either a quill or threadless system, and each system is compatible with respective headset and fork designs: The stem is the component on a bicycle that connects the handlebars to the steerer tube of the bicycle fork.
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