Cervelo S5 Supplementary Manual page 43

There are several different types and styles of shifting controls:
levers, twist 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 "lower" or "slower" gear, one which is easier to pedal.
An upshift is a shift to a "higher" or "faster", harder to pedal gear.
What's confusing is that what's happening at the front derailleur is
the opposite of what's happening at the rear derailleur (for details,
read the instructions on Shifting the Rear 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
least some tension. A derailleur will shift only if you are pedaling forward.
CAUTION: Never move the shifter while pedaling backward,
nor pedal backwards immediately after having moved 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
higher gear ratios. Pedaling in the
higher gears requires greater pedaling
effort, but takes you a greater distance
with each revolution of the pedal
cranks. The larger sprockets produce
lower gear ratios. Using them requires
less pedaling effort, but takes you a
shorter distance with each pedal crank
revolution. Moving the chain from a
smaller sprocket of the gear cluster to a
larger sprocket results in a downshift.
Moving the chain from a
larger sprocket to a smaller sprocket results in an upshift. In order
for the derailleur to move the chain from one sprocket to another,
the rider must be pedaling forward.
c. Shifting the Front Derailleur:
The front derailleur, which is controlled by the left shifter, shifts
the chain between the larger and smaller chainrings. Shifting the
chain onto a smaller chainring makes pedaling easier (a downshift).
Shifting to a larger chainring makes pedaling harder (an upshift).
Cervélo Owner's Manual
fig. 10
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