How to Replace a Crankset

The cranks on a bicycle are the arms that extend up and out from the toothed chain rings in the center of the bike frame. When the cranks spin, the chain moves, thus engaging the bicycle's drive train. Over time, cranksets wear out and require an upgrade or change. When changing out the crankset, be sure to match the length of the new cranks to the ones you take off the bike. Find the crank length imprinted on the inside of the crank arm, measured in millimeters.

Things You'll Need

  • Two 8mm hex wrenches
  • Pedal wrench
  • Bike work stand
Show More

Instructions

    • 1

      Place the bike in the stand and turn the cranks and shift the chain to the largest chain ring and smallest-toothed cog on the back of the rear wheel. Pull the chain up and off the chain rings near the cranks.

    • 2

      Use the pedal wrench and remove the pedals. Slip the crescent over the pedal screw and turn the wrench clockwise to unthread the pedals. Pedals thread in an opposite direction so as to prevent them from spinning off during use.

    • 3

      Insert the 8mm hex wrenches into the center hex screws on both sides of the cranks. Push and pull the wrenches so opposing force works to loosen the crank threads. Pull the cranks off and set them aside.

    • 4

      Place the new cranks on the screws and turn the hex screws counterclockwise to tighten them. Get them as tight as possible. Slide the chain back up and onto the chain rings and go out for a ride.