105
The purpose of having multiple gears on a bicycle is to let you chose the gear that allows you to maintain your optimum
cadence under the widest range of riding conditions. Depending on your fitness level and experience (the more fit, the higher
the cadence), optimum cadence is between 60 and 90 pedal revolutions per minute.
2. Shifting a derailleur drivetrain
If your bicycle has a derailleur drivetrain, the gear-changing mechanism will consist of:
• a rear sprocket cluster, called a freewheel or freewheel cassette
• a rear derailleur
• usually a front derailleur
• one or two shifters
• one or two control cables
• one, two or three front sprockets called chainrings
• a drive chain
The number of possible gear combinations (“speeds”) is the product of multiplying the number of sprockets at the rear of the
drivetrain by the number of sprockets at the front (6 x 2 = 12, 6 x 3 = 18, 7 x 3 = 21 and so on).
a. Shifting Gears
There are many different types of shifter mechanisms, each preferred for specific types of application
because of its ergonomic, performance and price characteristics. The designers of your bike have selected
the shifter design which they believe will give the best results on your bike.
The vocabulary of shifting can be pretty confusing. A downshift is a shift to a “slower” gear, one which is
easier to pedal. An upshift is a shift to a “faster”, harder to pedal gear. What’s confusing is that what’s hap
pening 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.
?
