Derailleur Maintenance
The modern derailleur systems are such that they are easily
adjusted should the need arise, and it is important to check
and adjust them periodically to get smooth shifting between
gears. Hesitation when shifting is a good indication that
adjustment is required; when you try to shift the chain and
it doesn’t quite engage the next gear the way it should.
The most probable cause is that the shifting cable has stretched,
which happens to all cables. To adjust the derailleur, stand
behind the bike and turn the barrel adjuster (the round knurled
piece) either counter-clockwise or clockwise in half-turn
increments until the shifting hesitation is eliminated. If
the derailleur is hesitating when shifting toward the spokes,
turn the barrel adjuster toward the spokes (counter-clockwise);
if it hesitates shifting away from the spokes, turn it away
from the spokes (clockwise). Only turn a half-turn at a time
and check to see if the hesitation is eliminated before turning
another half-turn increment.
It is very important to protect the derailleur. It is very
fragile and any damage to it can cause the shifting to malfunction.
Don’t let your bike fall on the derailleur, which
may bend it. When bent the derailleur can cause shifting
into the spokes. This can cause serious wheel damage. Signs
that indicate a bent derailleur are sudden hesitation shifting
in higher gears and a clicking sound when you are on your
top cog. If you hear this sound shift out of this, gear
immediately because the derailleur is hitting the spokes
and may go into the wheel.
Trouble
Shooting Tips For the Derailleur
Problem: The chain falls off while you are
shifting to the small chainring.
Solution: You can usually keep riding, but
pedal very gently and shift the derailleur. Hopefully, the
chain will shift back to the chainring.
Problem: When you stand to climb, the
chain rubs the derailleur.
Solution: Try adjusting the low-gear adjusting
screw so that there is more clearance between the cage and
the chain when in low gear.
Problem: When you stand to sprint, the
chain rubs the derailleur.
Solution: The chainring may be slightly
bent. Check it and have it trued if it is bent. Or you can
try adjusting the high-gear adjusting screw to provide more
clearance between the cage and the chain when in high gear.
Problem: The derailleur will not shift
to the smaller chainring.
Solution: Make sure the cable is moving
smoothly. Make sure the angle of the cage is parallel to
the chainrings, that the low-gear adjusting screw allows
the derailleur to move far enough to the inside, and that
the nose of the derailleur is slightly bent toward the chain.
Problem: The derailleur will not shift
to the larger chainring.
Solution: Check to see if the angle of
the cage is parallel to the chainrings, that the high-gear
adjusting screw allows the derailleur to move far enough
to the outside, and that the cage’s nose is slightly
bent toward the chain.
References
1. Langley, Jim. Bicycling Magazine’s Complete
Guide to Bicycle Maintenance and Repair or Road and Mountain
Bikes. Emmaus: Pennsylvania. 1999.
2. Milson, Fred. The Bike Book: Complete Step-By-Step
Guide to Choosing, Maintaining, and Repairing Your Bicycle.
Des Moines: Iowa. 1995.
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