1. How a derailleur drivetrain works
If your bicycle has a derailleur drivetrain, the gear-changing mechanism will have:
• a rear cassette or freewheel sprocket cluster
• a rear derailleur
• usually a front derailleur
• one or two shifters
• one, two or three front sprockets called chainrings
• a drive chain
a. Shifting Gears
There are several different types and styles of shifting controls: levers, t
wi
st grips, triggers, combination shift/brake controls
and push-buttons. Ask your dealer to explain the type of shifting controls that are on your bike, and to show you how they work.
The vocabulary of shifting can be pretty confusing. A downshift is a shift to a “lo
wer” or “slower” gear, one which is easier to
pedal. An up shift is a shif t to a “higher” or “faster”, harder to pedal gear. What’s confusing is that what’s happening at the front
derailleur is the oppos ite of what’s h appening at the rear dera illeur (for det ails, read the inst ructions on Shif ting the Rea r
Derailleur and Shifting the Front Derailleur below). For example, you can select a gear which will make pedaling easier on a hill
(make a downshift) in one of two ways: shift the chain down the gear “steps” to a smaller gear at the front, or up the gear “steps”
to a larger gear at the rear. So, at the rear gear cluster, what is called a downshift looks like an upshift. The way to keep things
straight is to remember that shifting the chain in towards the centerline of the bike is for accelerating and climbing and is called a
downshift. Moving the chain out or away from the centerline of the bike is for speed and is called an upshift.
Whether upshifting or downshifting, the bicycle derailleur system design requires that the drive chain be moving forward and
be under at lea
st some tension. A derailleur will shift only if you are pedaling forward.
CAUTION: Never mo ve th e sh ifter while p edaling b ackward, no r pedal b ackwards immed iately af ter h aving
move
d the shifter. This could jam the chain and cause serious damage to the bicycle.
b. Shifting the Rear Derailleur
The rear derailleur is controlled by the right shifter.
The function of the rear derailleur is to move the drive chain from one gear sprocket to another. The smaller sprockets on the
gear cluster produce hi gher gear ratios. P edaling in the h igher gears requires greater pedaling effort, but t akes you a greater
distance with each revo lution of the pedal cranks. The l arger sprockets produce l ower gear ratios. Using them requ ires less
pedaling effort, but takes you a shorter distance with each pedal crank revolution. Moving the chain from a smaller sprocket of the
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