How to Change a Three Piece Crank Sprocket

A three-piece bicycle crank includes two arms and either a pair or trio of sprockets. The arms are used to turn the crank, while the sprockets in turn drive the chain. Sprockets come in various sizes, with different size sprockets resulting in different size gear ratios. To allow an individual to customize gearing, sprockets are often interchangeable, and are generally attached, in a cluster, to the right, or drive side, crank arm. The sprockets are held in place by a series of fixing bolts.

Things You'll Need

  • 5 mm hex wrench
  • Flat blade screwdriver
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Instructions

  1. Crank Sprocket Removal

    • 1

      Fit a 5 mm hex wrench into the first fixing bolt. The bolts are located on the face of the outer sprocket. There may be as many as five bolts, each one attaching a point of the sprocket to the arm of the crank.

    • 2

      Use a flat blade screwdriver to hold the fixing bolt nut in place. The nut is located on the backside of the sprocket. There is a slot in the nut designed to accommodate the head of the screwdriver.

    • 3

      Turn the 5 mm hex wrench counterclockwise to loosen and remove the bolt. Grab the nut from the backside and place it with the bolt.

    • 4

      Remove the remainder of the fixing bolts and each of their nuts.

    • 5

      Slide the sprockets one a time over the crank arm. Choose which sprocket is to be changed.

    Crank Sprocket Installation

    • 6

      Slide the smallest sprocket first over the crank arm and onto the crank. Follow by sliding the larger sprocket over the crank arm.

    • 7

      Align the sprockets with their attachment points on the crank. The largest sprocket may have a knob on its outer surface. The knob, called a "chain drop prevention pin", is designed to catch the chain if the chain ever slips off the sprocket. Align the knob with the crank arm.

    • 8

      Install the first fixing bolt. Hold the fixing bolt nut in place, on the backside of the sprocket, using the flat head screwdriver.

    • 9

      Tighten the fixing bolt, using the 5 mm hex wrench.

    • 10

      Install each of the fixing bolts in turn.