How to Fix a Shimano STX

Shimano STX bicycle shifters are some of the most common mountain bike shifters on the market. They come standard on Trek, Specialized, Giant and many other bikes for good reason. STX shifters are inexpensive, accurate, easy to work on and reliable. However, like all bike shifters, eventually STX shifters will go out of adjustment and need repair. Learn how to fix your Shimano STX shifters at home and save time and money over taking your bike to the local bike shop.

Things You'll Need

  • 5mm hex wrench
  • Phillips screwdriver
  • Needle-nose pliers
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Instructions

    • 1

      Locate the cable stop bolt of the front and rear derailleurs. This is the bolt that clamps the shifter cable down, effectively connecting the shifter to the derailleur. Loosen both cable stops, using a 5mm hex wrench, then pedal the bike forward a few rotations to settle the derailleurs. Click the downshift lever on both shifters, located on the top of the shifter, until both shifters are in their lowest gears.

    • 2

      Inspect the alignment of the small cog, which the chain is currently sitting on, and the pulleys of the rear derailleur. The chain should form a straight, vertical line between the cog and pulley. If the chain is being pulled to the right by the pulley, tighten the high-limit screw -- marked with an H -- of the rear derailleur, using a Phillips-head screwdriver, until it lines up properly. If the chain is being pulled to the left by the pulley, loosen the high-limit screw until it is aligned.

    • 3

      Pull the rear derailleur cable tight underneath the cable stop bolt loosened previously, using a set of needle-nose pliers. Tighten the cable stop bolt with a 5mm hex wrench to hold the cable securely in place. Spin the cranks of the bike forward and shift through the gears on the right shifter to be certain the rear derailleur now works properly.

    • 4

      Inspect the alignment of the chain with the front derailleur cage from above the bike. Spin the cranks and listen for any rubbing or chain-and-cage contact. If the chain rubs on the cage, tighten the low-limit screw -- marked with an L, using a Phillips-head screwdriver until the rubbing stops. Pull the front derailleur cable tight underneath the front derailleur cable stop bolt you loosened previously. Tighten the cable stop bolt, using a 5mm hex wrench to hold the cable in place.

    • 5

      Spin the cranks of the bike forward and shift through each of the gears on the left shifter to ensure every gear works properly. Take your bike out for a quick test ride. Bicycles act differently when you put your weight on them, so a test ride in necessary to ensure that it is adjusted properly. Since you have effectively set the shifter system of your bike back to the stock configuration, it should shift smoothly and quickly through each of the gears.