Stem

The stem connects the handlebars to the fork's steerer tube. It determines reach and stack height (along with frame geometry, fork length, and spacers).

Key stem specs:

• Length — common range is 70–130mm. Affects reach.
• Angle — typically ±6° to ±17°. Affects stack/handlebar height.
• Steerer clamp diameter — usually 1-1/8".
• Bar clamp diameter — usually 31.8mm; some 35mm and older 26mm.

Stems are one of the most fit-relevant components. A change of 10mm in stem length is noticeable. Always re-tape bars and re-route cables when changing stems.

Some modern aero bikes use proprietary integrated stem/handlebar combinations that are not interchangeable with separate stems.