How to Repair a Bicycle Arm

Cycling is one part exercise, one part recreation and one part mechanical hobby. The avid cycling enthusiast either has to have a huge budget for visits to the bike repair shop or has to become an amateur bicycle mechanic. Even large, die-cast parts like the bicycle crank arm can become damaged and need to be replaced. There are several types of bicycle crank arms, so knowing the correct replacement procedure for your type of crank arm is crucial.

Things You'll Need

  • Bicycle
  • Replacement bicycle crank arm
  • Hex-head driver set
  • Crank extractor
  • Socket set
  • Wrench set
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Instructions

  1. Determining Type of Crank Arm

    • 1

      Remove the protector cap if there is one in place over the spindle of the crank arm.

    • 2

      Remove the retaining bolt with a hex-head driver.

    • 3

      Check the spindle area to determine the type of crank arm. If the spindle ends in a threaded bolt with a nut holding the crank onto the spindle, you have a male-threaded spindle crank. If you find a ring with teeth, you have a splined crank. If the crank is held in place on the spindle by a bolt, you have the most common type: female-threaded spindle crank.

    Female-Threaded Spindle Crank

    • 4

      Remove the bolt from the spindle with a hex-head driver.

    • 5

      Screw the thick end of a crank extractor into the threads of the spindle by hand.

    • 6

      Screw the core of the crank extractor by hand into the smaller end of the crank extractor.

    • 7

      Apply the crank extractor handle to the core and turn it until the crank arm comes loose from the spindle.

    • 8

      Slide the replacement crank arm onto the spindle and screw it into place with the retaining bolt, using a hex-head driver.

    Splined Crank

    • 9

      Insert a hex-head driver into the opening at the base of the crank and turn it counter-clockwise until the bolt and dust cap are loose.

    • 10

      Slide the crank arm off the bottom bracket.

    • 11

      Place the new crank arm on the bottom bracket and secure it in place with the spindle bolt, using a hex-head driver.

    Male-threaded Spindle Crank

    • 12

      Remove the retaining nut with a socket driver.

    • 13

      Remove the nut from the spindle with a wrench.

    • 14

      Insert the big end of a crank extractor by hand into the threads of the crank.

    • 15

      Screw the core of the crank extractor by hand into the small end of the crank extractor.

    • 16

      Apply the crank extractor handle and turn it until the crank comes loose.

    • 17

      Remove the crank and slide the replacement crank onto the spindle.

    • 18

      Secure the replacement crank in place with a hex-head driver and replace the plastic protector cap.