you know how a derailleur
works, you can fix many bike
problems on your own.
/ BY JAMES LYNCH /How to
Adjust a
Derailleur
ERAILLEURS ARE THE
transmission of your
bike. When you shift,
they guide the chain
to the correct gears.
Whether you’re fixing
a particular problem
with your chain or simply giving
the system a tune-up now that
spring is here, here’s how to do it.- Start by putting your bike on
a bike stand to get the rear wheel
off the ground. Turn the pedals
by hand and shift through your
gears. If there’s a lag between
when you shift and when the
chain moves, the tension on the
cables going from your shift-
ers to the derailleurs is off, and
you need to unscrew the barrel
adjuster (the black cylinder on
the derailleur cable) to increase
the tension. If the chain jumps
between gears on its own, tighten
the barrel adjuster to add tension. - Shift to high gear. The chain
w ill be on the sma llest ring in the
rear and the largest ring in the
front. On the rear derailleur, find
high and low limit screws (labeled
H and L). They control how far
the derailleur can move. Tighten
the H screw on the rear derailleur
until the chain does not click as it
moves through, but leave it loose
enough that the chain can still
shift from the second smallest
gear to the smallest. - Finally, shift to low gear. The
chain will be on the largest ring
in the rear and the smallest ring
in the front. Tighten the L screw
until the derailleur can move
only as far as the largest gear
and not past it. But keep it loose
enough that the chain still moves
from the second largest ring to
the largest ring with ease when
shifting. It might take a few tries. - On the front derailleur, adjust
the L screw until the inner side of
the cage that encircles the chain
is as close as possible to the chain
without scraping against it.
Shift both derailleurs into high
gear. Adjust the H screw until
the outer edge of the cage is as
close to the chain as possible
without scraping.
D
@PopularMechanics _ April 2019 49Our expert: Savannah Quandt,
bike mechanic at Scheels in
Johnstown, Colorado