How to Adjust a Shimano Derailleur

How to Adjust a Shimano Derailleur
The derailleur serves a crucial role in the shifting of your bicycle's gears. Responding to tension from the shifter cable, the derailleur moves the drive chain from one gear to another. If not properly adjusted, the derailleur will fail to transfer the chain an adequate amount of distance, resulting in inaccurate shifting. Before beginning any adjustments on your Shimano derailleur, replace any shifter cables that are visibly damaged or are over a year old. Damaged or old cables may not hold adjustments accurately.
 

Instructions

Difficulty: Easy

Rear derailleur

Things You’ll Need:
  • 5mm Allen wrench
  • Phillips screwdriver
  • Needle-nose pliers
 
Step 1
Shift gears so that the chain rests on the smallest rear sprocket and largest front chainring. Using a 5mm Allen wrench, loosen the bolt that anchors the shifter cable to the rear derailleur.
Step 2
Kneel behind the bike and check the alignment of the upper derailleur pulley with the sprocket directly above it. The two should be perfectly in line. If adjustment is needed, turn the H-limit screw on the derailleur until the two are in line. The screw will be marked with the letter 'H' and will require a Phillips screwdriver.
Step 3
Pull the end of the shifter cable taught with a pair of needle-nose pliers and re-tighten the anchor bolt over the cable.
Step 4
Try shifting to the next sprocket over. If the chain hesitates or refuses to shift, give the adjuster barrel, located where the shifter cable enters the body of the derailleur, a ¼ turn in toward the bike. Continue to turn until the chain shifts cleanly.
Step 5
Shift the chain the innermost rear sprocket and front chainring combination. If the chain does not fully shift or shifts too far, turn the L-limit screw to make adjustments. Turning the screw clockwise moves the derailleur away from the bike.

Front derailleur

Step 1
Shift the chain to the innermost rear sprocket and front chainring combination. As recommended by parktool.com, you should see a 1mm gap between the derailleur cage plate and chain. To adjust the gap, turn the front derailleur L-limit screw until the gap is achieved. Turning the screw clockwise will lessen the gap.
Step 2
Shift the chain to the large chainring. If the chain shifts sluggishly or not at all, increase tension upon the shifter cable by turning the adjuster barrel in toward the bike. On road bikes, the adjuster barrel will be found on the downtube of the frame. Adjuster barrels on mountain bikes can usually be found where the shifter cable enters the body of the shifter.
Step 3
Check the gap between the derailleur cage plate and the chain. Once again this gap should be neither more nor less than 1 mm, or approximately the width of a dime. To adjust the gap, turn the H-limit screw. Turning the screw clockwise will lessen the gap.
 

Tips & Warnings

 
Always check your adjustment before riding. It further adjustments are needed, perform them at home rather than out on the road, where you may not have access to necessary tools.

Article Written By Matthew Ferguson

Matthew Ferguson is a writer living in Savannah, Ga. He has been writing for over 10 years and his work has appeared on various online publications. A collection of his short stories was published in spring 2010. He is a graduate of Appalachian State University.

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