3.13 drivetrain

Bottom Bracket Installation — External Cup

Bottom Bracket Installation — External Cup. Step-by-step procedure for bike maintenance — tools, time, and what to watch out for.

Difficulty ★★★ advanced
Time ~15 min
Applies to Bikes with threaded external-cup BB

Tools

  • Standard workshop tools

Procedure

  1. Apply grease or anti-seize

    to the BB shell threads — abundantly. Steel cups in aluminum frames can corrode together; grease prevents this.

  2. Identify drive vs non-drive cup.

    They're often labeled "L" and "R" (referring to their position on the bike).

  3. Hand-thread each cup

    into the correct side. Verify smooth threading — if it binds, back off and realign.

  4. Tighten with the BB tool

    to **35–50 Nm** (check manufacturer spec).

  5. Reinstall crankset

    (3.11). ---
  1. Apply grease or anti-seize to the BB shell threads — abundantly. Steel cups in aluminum frames can corrode together; grease prevents this.
  2. Identify drive vs non-drive cup. They’re often labeled “L” and “R” (referring to their position on the bike).
  3. Hand-thread each cup into the correct side. Verify smooth threading — if it binds, back off and realign.
  4. Tighten with the BB tool to 35–50 Nm (check manufacturer spec).
  5. Reinstall crankset (3.11).