Many geared bicycles feature derailleurs that shift the chain from one sprocket or chain ring to another. A front derailleur includes the derailleur cage and attachment clamp. On so-called top swing derailleurs, the cage and clamp are located one above the other, respectively. Like any other derailleur, Shimano top-swing derailleurs are adjusted periodically to ensure optimal performance.
Use the gear shifters to shift the chain to the innermost rear cog and front chain ring combination.
Use a 5 mm Allen key and loosen the pinch bolt securing the cable to the front derailleur. The cable will go slack. Do not remove the bolt fully.
Inspect the gap between the chain and the front derailleur cage. The cage is the portion of the derailleur through which the chain passes. The gap should be 1 mm or about the thickness of a dime.
Use a Phillips screwdriver and turn the screw marked with an “L” atop the derailleur to adjust the gap. Turning the screw clockwise will move the derailleur cage closer to the chain.
Locate the cable adjuster barrel, where the cable enters the body of the shift lever. Turn the barrel all the way into the shift lever and then back it out two full turns.
Pull the end of the cable tight, and retighten the derailleur pinch bolt onto the cable.
Use the gear shifters to shift the chain to the outermost rear cog and front chain ring combination. If the front derailleur does not shift the chain, turn the cable barrel adjuster beside the shift lever away from the lever, and try again. Continue this adjustment until the chain shifts onto the large chain ring.
Inspect the gap between the chain and the front derailleur cage once again. In this position, too, the gap should be 1 mm.
Turn the screw marked with an “H” atop the derailleur to adjust the gap. Turning the screw clockwise will move the derailleur cage closer to the chain.
Use the gear shifters to shift the chain to the innermost rear cog and middle front chain ring. Check the gap between the derailleur cage inner plate and the chain. According to Shimano, the gap should be 0.5 mm.
Adjust the gap as needed by turning the barrel adjuster beside the shifter. Turning the barrel adjuster away from the body of the shifter moves the derailleur cage inner plate closer to the chain.