Deore is a line of bicycle components produced by Shimano. Separate shifters control the front and rear gears, with the front gear shifter located on the left side of the handlebar and the rear gear shifter on the right. Each shifter employs a cable to operate a mechanism called a derailleur. A derailleur is located under each set of gears. The cable causes the derailleur to pivot and carry the chain to the desired gear. Shifter cables are replaced when overly worn.
Operate the gear shifter as many times as takes to give the shifter cable maximum slack.
Locate the screw on the body of the front Deore shifter that hides the shifter cable head. This screw is directly opposite where the cable enters the body of the Deore model shifter.
Use a Phillips head screwdriver to remove the screw. Set the screw in a secure place.
Follow the shifter cable from the shifter to its derailleur. Remember this path. The replacement cable will follow the same path once installed.
Use a 5mm Allen key to loosen the cable pinch bolt on the Shimano Deore derailleur. This bolt secures the shifter cable to the derailleur.
Use a pair of wire cutters to clip off the metal end cap from the end of the cable.
Pull the cable free of the derailleur. Push the cable up to cause the cable head to emerge from the body of the shifter.
Grasp the head of the shifter cable and remove the cable from the shifter.
Thread the new cable through the feed hole in the body of the shifter. Pull the other end of the cable to seat the cable head inside the shifter.
Route the new cable to its derailleur through the cable housing, following the same path as the old cable.
Locate the cable tension adjuster barrel. Depending on which shifter cable is being replaced, the adjuster barrel can be found either at the back of the derailleur or beside the body of the Shimano Deore shifter.
Turn the adjuster barrel clockwise until it no longer turns. Then turn it counterclockwise twice.
Grab the end of the cable and route it beneath the derailleur cable pinch bolt. Secure the pinch bolt onto the cable, using the 5mm Allen key.
Use the gear shifter to shift to the next gear over. If the derailleur fails to shift the chain, turn the barrel adjuster counterclockwise and try again. Continue the adjustment until the shift is successful.
Use cable cutters to cut the end of the shifter cable at a point 2 inches beyond the derailleur pinch bolt.
Press a metal end cap onto the end of the cable. Squeeze the cap onto the cable using needle nose pliers.
Replace the screw on the body of the shifter. Use the Phillips screwdriver to turn the screw clockwise until it stops. Shimano warns that overtightening the screw can damage its threads.