How to Install an External Bearing Bottom Bracket

An external bottom bracket is a set of bearings that allows the crank of a bicycle to spin around. Rather than housing the bearings inside the frame, however, the bearings of an external bottom bracket system are housed in a separate outer ring. This makes it possible to use a two-piece crank, and makes the bottom bracket area of the bike stiffer and more responsive to pedaling force.

Things You'll Need

  • External bottom bracket tool
  • Adjustable wrench
  • 5 mm hex wrench
  • Thread grease
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Instructions

    • 1

      Grease the threading on both the external bottom bracket cups and the inside threads of the frame's bottom bracket. This will keep the cups from seizing in the frame, making them easy to remove and replace later.

    • 2

      Thread the right side bottom bracket cup into the right side of the frame clockwise. Thread by hand until it becomes too hard to turn. At this point, attach an external bottom bracket tool to the outside of the cup, and use an adjustable wrench to tighten it firmly.

    • 3

      Thread the left side bottom bracket cup into the left side of the frame counterclockwise. These threads are usually reverse-threaded. Attach the external bottom bracket tool to the outside of the cup and use an adjustable wrench to tighten it firmly against the frame.

    • 4

      Slide the spindle attached to the right crank-arm into the bottom bracket from the right side of the frame. Make sure the spindle is pushed all the way through the bottom bracket.

    • 5

      Attach the left crank arm to the end of the spindle that is protruding from the bottom bracket. Make certain that the left and right crank arms are perfectly parallel. Thread the rubber dust-cap into the spindle through the left crank arm.

    • 6

      Tighten the two left side crank arm bolts using a 5 mm hex wrench. Hold both crank arms and pull them side to side in the frame to feel for play in the bottom bracket. If you don't feel or hear any clicking or popping, the bottom bracket is installed correctly. If you do, however, remove the left side crank arm and reinstall it, as it is not tight enough to ride on.