How to Adust Shimano Derailleurs

How to Adust Shimano Derailleurs
Most geared bicycles will contain both front and rear gears, and for each set of gears there is a derailleur responsible for moving, or derailing, the chain from one gear to another. Shimano is one of the world's most renowned manufacturers of bicycle components, and Shimano derailleurs have proven to be reliable and easy to maintain and adjust. Derailleurs are located at two points on the bicycle: just above the front chain rings and just below the rear cassette.
 

Instructions

Difficulty: Moderately Easy

Rear Derailleur

Things You’ll Need:
  • 5mm Allen wrench
  • Needlenose pliers
  • Cable crimps
 
Step 1
Shift to the smallest rear cog and largest front chain ring. Loosen the cable anchor bolt located on the bottom of the derailleur body. The bolt probably will require a 5mm Allen wrench. Loosening the bolt releases the tension on the cable, allowing you to make adjustments.
Step 2
Stand behind the bike and check the alignment of the upper derailleur pulley beneath the cog. The two should be perfectly in line. If not, turn the high-range screw on the derailleur body until the pulley is directly beneath the cog. The screw will be marked with an "H".
Step 3
Pull all slack from the derailleur cable with a pair of needle nose pliers and re-tighten the anchor bolt with a 5mm Allen wrench.
Step 4
Shift the chain onto the next cog. If the chain refuses to shift, or shifts sluggishly, turn the adjusting barrel, located at the rear of the derailleur, toward the bike. Turn the barrel until the chain rests evenly on the next cog.
Step 5
Shift the chain to the largest rear cog and smallest front chain ring. If the chain refuses to shift onto this cog, turn the low-range screw counter-clockwise. If the chain shifted past the cog, turn low-range screw clockwise. The screw will be marked with an "L".

Front Derailleur

Step 1
Shift the chain onto the largest rear cog and smallest front chain ring. Loosen the cable anchor bolt just above the front derailleur.
Step 2
Check the gap between the derailleur cage and the chain. Adjust to about a 2 mm gap, roughly the width of a penny. To lessen the gap, turn the low-range screw atop the derailleur counter-clockwise. To increase the gap, turn the same screw clockwise.
Step 3
Shift the chain onto the large chain ring and the smallest rear cog. If the chain refuses to shift, or shifts sluggishly, turn the adjusting barrel in toward the bike. For road bikes, the adjusting barrel will be located on the downtube of the frame. For mountain bikes, the shifter probably will be found where the cable enters the shifter.
Step 4
Check the gap between the derailleur cage and the chain. Once again there should be about a 2 mm gap between the two. Turning the high-range screw clockwise will lessen the gap. Turning the screw counter-clockwise will increase it.
 

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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