How to Install a Bottom Bracket on a Shimano 105

Written by matthew ferguson
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How to Install a Bottom Bracket on a Shimano 105
(Hemera Technologies/ Images)

A Shimano 105 bottom bracket houses two sets of sealed bearings and an axle. A fixed cup and an adjustable cup allow the bottom bracket to thread into the bottom bracket shell of the bicycle frame. A crank set is then attached to the bottom bracket axle. The two sets of bearings, one on either side of the bottom bracket, allow the crank set and axle to rotate smoothly.

Skill level:
Moderately Easy

Things you need

  • Bicycle grease
  • Shimano compatible splined bottom bracket tool
  • Adjustable wrench

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  1. 1

    Grease the threads on the fixed cup. The fixed cup is attached to one end of the Shimano 105 bottom bracket.

  2. 2

    Slide the non-fixed cup end of the bottom bracket through the right, drive-side of the bottom bracket shell on the bicycle frame. The bottom bracket shell is the hollow cylinder at the base of the frame.

  3. 3

    Turn the bottom bracket counterclockwise to tighten. Turning the bottom bracket by hand initially prevents crossthreading it.

  4. 4

    Install the Shimano-compatible splined bottom bracket tool against the right-drive side of the bottom bracket. Attach an adjustable wrench to flat portion of the bottom bracket tool.

  5. 5

    Use the adjustable wrench to continue tightening the bottom bracket. Remember to turn this end of the bottom bracket counterclockwise to tighten.

  6. 6

    Grease the threads of the adjustable cup.

  7. 7

    Thread the adjustable cup into the left, non-drive side bottom bracket shell. Turn the cup clockwise to tighten.

  8. 8

    Use the adjustable wrench and splined bottom bracket tool to fully tighten the left, non-drive side cup.

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