How to Adjust Derailleurs After Changing the Cable

Derailleurs are critical components in the mechanism that allows a multi-speed bicycle to be shifted from one gear to the next. A functioning derailleur smoothly pushes the chain onto the next higher or lower sprocket. Gears that don't shift smoothly create unwanted noise and friction, slowing you down and adding wear and tear to your bicycle. After replacing the cables that control the gearing system, you will need to make some delicate adjustments to the derailleurs. Adjusting your bike's derailleurs is a straightforward procedure and doesn't require specialized tools or expert mechanical knowledge.

Things You'll Need

  • Phillips screwdriver
  • Allen wrenches
  • Lubricating oil
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Instructions

  1. Front Derailleur Adjustment

    • 1

      Rest the bike on a stand so that the rear wheel turns freely and you can turn the pedals by hand.

    • 2

      Shift the rear derailleur to the largest sprocket. Then shift the front derailleur to the smallest sprocket.

    • 3

      Loosen the cable tension to the front derailleur by turning the Allen screw a couple of turns counterclockwise. Find the correct Allen screw by following the cable down into the derailleur assembly.

    • 4

      Pull the front derailleur towards you after relaxing the cable tension. Ensure that the mechanism completely clears the largest sprocket. Ease the derailleur back into position.

    • 5

      Turn the L-screw until the derailleur doesn't touch the chain. Allow about 2 mm of clearance between the chain and outer guide of the front derailleur. When properly adjusted, add tension back to the cable.

    • 6

      Shift the rear derailleur to the smallest sprocket, and shift the front derailleur to the largest sprocket.

    • 7

      Check for proper clearance between the front derailleur assembly and the chain. Turn the front H-screw until the derailleur permits the chain to move unobstructed. Shift through each gear on the front cassette, adjusting cable tension in small increments to improve performance.

    Rear Derailleur Adjustment

    • 8

      Inspect the rear derailleur assembly for damage. Look at the assembly from the rear and confirm that the pulleys are in perfect vertical alignment. Replace a damaged derailleur before proceeding.

    • 9

      Inspect the chain for rust or kinked links. Prop the bike on a stand and turn the pedals backward, looking for problems in the chain. A jerky or bouncing motion in the chain indicates a bad link. Add some lubricating oil to the chain if it appears dry.

    • 10

      Shift the rear derailleur to the highest gear while turning the pedals. The highest gear is the smallest, outermost sprocket on the rear cassette.

    • 11

      Check the alignment of the derailleur pulleys with the sprocket. The pulleys should hang directly beneath the smallest sprocket. Even a slight misalignment to the inside or outside will cause problems in your gearing.

    • 12

      Turn the H-screw on the rear derailleur clockwise if the pulleys hang too far outside. This will bring them back into line. If they are too far inside and the chain rubs on the next sprocket, then turn the H-screw counterclockwise. Turn the screw one half-turn at a time and observe the results. Stop when the pulleys and the smallest sprocket are in perfect alignment.

    • 13

      Shift to the next gear. The transition should be fast and quiet. If the chain clatters or resists moving to the next sprocket, increase cable tension by turning the barrel adjuster one full turn clockwise. Stop turning when the derailleur pulleys and sprocket go into alignment. Try shifting between the two highest gears to ensure that alignment and tension are fine-tuned.

    • 14

      Shift up to the lowest sprocket, which is the largest and innermost on the rear cassette. Adjust cable tension if any of the middle gears fail to shift smoothly.

    • 15

      Check the alignment of the pulleys and the large sprocket. The pulleys should hang directly underneath. If they're too far inside, turn the L-screw clockwise until the pulleys move to the correct position. Turn the L-screws counterclockwise if the pulleys need to move further inside.