How to Fix the Shimano Gears on an Old Road Bicycle

How to Fix the Shimano Gears on an Old Road Bicycle
Shimano gears on an older bicycle will differ from newer versions primarily in their design; the gear shifters (called downtube shifters) will be located on the downtube of the frame rather than attached to the handlebar. The two designs share the same principle, however. A cable pulls a derailleur, which in turn shifts the chain onto the chosen gear. When the chain no longer shifts or shifts slowly, the problem can often be fixed by adjusting the range of the derailleur and adding proper tension to the shifter cable.

Instructions

Difficulty: Moderately Easy

Rear Gears

Things You’ll Need:
  • Allen keys
  • Needle-nose pliers
Step 1
Shift to the smallest rear cog and loosen the anchor bolt securing the cable in place on the rear derailleur.
Step 2
Check the alignment of the lower derailleur pulley with the cog above. Are the two in line? If not, turn the high-range screw located on the derailleur until the two are in line. The screw will be marked with an "H."
Step 3
Pull all slack from the cable by holding the end with a pair of needle-nose pliers. Re-tighten the cable anchor bolt.
Step 4
Shift the chain over to the next cog. If the chain refuses to shift, alter tension on the cable by turning the adjusting barrel in toward the bike a quarter-turn. The barrel is located where the cable enters the back of the derailleur.
Step 5
Shift the chain to the largest rear cog and shift the front gear to the inside chain ring. This is the cog closest to the bicycle. If the chain overshifts the cog or does not shift far enough, adjust the low-range screw, marked with an "L."

Front gears

Step 1
Shift the front gear to the smallest front chain ring. The rear gear should be shifted to the largest cog.
Step 2
Loosen the cable anchor bolt. The bolt will be located at the top of the derailleur body.
Step 3
Check the clearance between the front derailleur and the chain. Parktool.com recommends no more than 1mm in width. This is about the width of a penny. Adjust the gap if necessary. Turn the low-range screw located on the derailleur until a 1mm gap is achieved.
Step 4
Pull all slack from the cable with your needle-nose pliers. Re-tighten the anchor bolt, securing the cable.
Step 5
Shift to the largest front chain ring. Shift the rear gear to the smallest cog. Check the gap between the derailleur and the chain. Again, a 1mm gap is ideal. Adjust the gap by turning the high-range screw.

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.

Never Miss a Single Post

All our latest outdoor content delivered to your inbox once a week.

FREE UPDATES

Subscribe

We promise to keep your email address safe and secure.