Threadless Stem - Cycle Training Ireland

Threadless Stem

Threadless stems, as the same suggest clamp onto the outside of a unthreaded fork steerer
The stem (A) then clamps around the outside of the steerer tube along with spacers (B) if necessary. Finally, a top cap (C) keeps everything in place and acts as a headset adjustment.

Threadless stems will typically have 1–3 pinch bolts (D) used in conjunction with a compression slot (E) to hold the stem to the steerer tube. They will also have 2–6 bolts (F) securing the faceplate (G)

Spacers can be used to raise or lower the stem height providing the steerer tube length is suffice to accommodate the spacers
Stems come in different steerer tube and handlebar sizes (we will come back to handlebar sizes later).
It is wise to measure your components to ensure that you are installing or ordering the correct stem.
Common steerer tube diameters are: 25.4mm (1″), 1 ⅛”, 1 ¼” and 1 ½”.
To determine the diameter of the steerer tube, measure right where the stem will clamp using a metric caliper. Be sure to be accurate as some clamp diameters are within fractions of a millimeter of each other and are not cross-compatible.
It is difficult to determine the clamp diameter of the stem by measuring it. The clamp diameter is typically engraved or labeled on the stem, but sometimes it is not.
Incompatible components can be a safety hazard, so always double-check with the manufacturer for specifications and compatibility information.
Stems also come in different lengths — measured from the center of the steerer tube to the bar center — and angles — typically between 0 and 20 degrees. These measurements are generally marked somewhere on the stem or its packaging. Stems can be installed in an up or down position to adjust the bar height without changing spacer orientation. This is often referred to as positive and negative rise.
When Installing the new stem and spacers. Set the bike on the ground and ensure that all components are fully seated, with no gaps

Configure the stem and spacers to the desired stem height.
The stem or spacers should be slightly above the top of the steerer tube (approximately 3mm). If they are flush with or below the steerer tube, headset adjustment will be impossible. Acquire additional or differently-sized spacers to reach the appropriate height. It is also possible that the new stem is taller which may require you to remove a spacer.

Apply grease to the top cap bolt and install the top cap. The top cap sets the headset adjustment. Slightly snug this bolt for now — we will fine-tune this adjustment near the end of the process.
Snug the top cap down until there is slight resistance.
Test the headset adjustment by lifting the bike and pushing the bars back and forth — the bars should turn freely with very little resistance.
If the motion of the bars feels sticky or hesitant, loosen the top cap 1/8th of a turn and test again

Next, straighten the handlebars. It can be helpful to use a ruler or other long object against the fork legs as a reference point.
Snug the pinch bolts. Test the headset adjustment by holding the front brake firmly and rock the bike back and forth. Put your fingers on the top bearing cover of the headset and the top cup of the headset and feel for play, which can be felt as a slight knock.
It may also help to turn the handlebars 90 degrees — this isolates fork play.
If you feel play, loosen the pinch bolts, tighten the top cap another 1/8th turn, re-tighten the pinch bolts, and check again. continue until the play is gone. Verify that the bars still turn freely with little resistance.
Torque the pinch bolts. A typical torque spec is 4–6 Nm. But check for a torque figure printed on the stem or in the manufactures installation manual.