How to Remove a Shimano Bottom Bracket from a Bicycle

Written by clayton guebert
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How to Remove a Shimano Bottom Bracket from a Bicycle
Those who ride a lot will eventually have to replace the bottom bracket on their bikes. (woman on a bicycle image by Wimbledon from Fotolia.com)

The bottom bracket is the set of bearings that allows a bicycle's crank arms to spin. It is an essential component for any bicycle, and without a functioning bottom bracket, it's basically impossible to operate the bike. If you put a lot of miles on your bike, the bottom bracket is something that will eventually wear out and need to be replaced. Most low-end road and mountain bicycles have square-taper bottom brackets, which are easy to remove with the right tools.

Skill level:
Moderate

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Things you need

  • Crank puller
  • 8mm Allen wrench
  • Bottom-bracket tool
  • Adjustable crescent wrench
  • Rag
  • Degreaser

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Instructions

  1. 1

    Shift the bicycle's front derailleur into the smallest chain ring. Use your hands to remove the chain from the chain ring. Rest the chain around the frame so that it doesn't obstruct the chain rings.

  2. 2

    Unthread and remove the crank bolts on both crank arms using an 8mm Allen wrench.

  3. 3

    Thread the crank remover into the holes on the crank arms where the crank bolts were. Once the crank remover is secure in the crank arm, tighten the lever on the crank remover until the crank arm comes off the spindle. Do this for both crank arms.

  4. 4

    Insert the bottom-bracket tool into the nondrive, or left, side of the bottom bracket. Use an adjustable crescent wrench to turn the bottom-bracket tool to the left to remove the bottom-bracket cup from the frame. Once the cup is removed, go to the drive, or right, side of the bicycle. Insert the bottom-bracket tool into the bottom bracket. The right side is reverse-threaded, so turn the bottom-bracket tool with the adjustable crescent wrench to the right to loosen the bottom bracket until you can remove it from the frame.

  5. 5

    Use a rag and some degreaser to clean grease and dirt out of the bottom-bracket shell in the frame.

Tips and warnings

  • Use a bicycle stand to get better leverage on the bike when you're working on it.
  • Make sure the bottom-bracket tool is fully seated in the bottom bracket when you turn it. If it isn't, it could come out unexpectedly and strip the bottom bracket.

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