frogbikes.com
Frog Bikes
Owner’s Manual
3
rd
Edition
2014
C2. How Brakes Work
The braking action of a bicycle is a function of the friction between the braking
surfaces. To make sure you have maximum friction keep your wheel rims and brake
pads or the disc rotor and caliper clean and free of dirt, lubricants, waxes or polishes.
When you apply one or both brakes, the bike begins to slow, but your body wants to
continue at the speed at which it was going. This causes a transfer of weight to the
front wheel (or, under heavy braking, around the front wheel hub, which could send
you flying over the handlebars). A wheel with more weight on it will accept greater
brake pressure before lockup; a wheel with less weight will lock up with less brake
pressure. So, as you apply brakes and your weight is transferred forward, you need
to shift your body towards the rear of the bike to transfer weight back on to the rear
wheel; and at the same time, you need to both decrease rear braking and increase
front braking force. This is even more important on descents, because going downhill
shifts weight forward.
Two keys to effective speed control and safe stopping are controlling wheel lockup
and weight transfer. This weight transfer is even more pronounced if your bike has a
front suspension fork. Front suspension “dips” under braking, increasing the weight
transfer (see also Section 4.F). Practice braking and weight transfer techniques where
there is no traffic or other hazards and distractions.
Everything changes when you ride on loose surfaces or in wet weather. It will take
longer to stop on loose surfaces or in wet weather. Tyre adhesion is reduced, so
the wheels have less cornering and braking traction and can lock up with less brake
force. Moisture or dirt on the brake pads reduces their ability to grip. The best way to
maintain control on loose or wet surfaces is to go more slowly.
D. Shifting Gears
Your multi-speed bike will have a derailleur drivetrain (see 1. below), an internal gear
hub drivetrain (see 2. below) or, in some special cases, a combination of the two.
D1. How a Derailleur Drivetrain Works
If your bike has a derailleur drivetrain, the gear-changing mechanism will have:
• a rear cassette or freewheel sprocket cluster
• a rear derailleur
• sometimes a front derailleur
• one or two shifters
• one, two or three front sprockets called chain-rings
• a drive chain
i. Changing gears
There are several different types and styles of gear selectors, or shifters: levers, twist
grips, triggers, combination shift/brake controls and push-buttons. Ask your stockist
to explain the type of shifting controls on your bike, and show you how they work.
The vocabulary of shifting gears can be confusing. A downshift is a change to a
“lower” or “slower” gear, one which is easier to pedal. An upshift is a shift to a “higher”
or “faster” gear which is harder to pedal. 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 key is to
remember that shifting the chain in towards the centre of the bike is for accelerating
and climbing and is called a downshift. Moving the chain out or away from the bike is
for speed and is called an upshift.
Whether upshifting or downshifting, the derailleur system requires the drive chain to
be moving forward and be under at least some tension. A derailleur will shift only if
you are pedaling forward.
CAUTION:
Never move the gear selector or shifter while pedaling backward, nor
pedal backwards immediately after changing gear. This could jam the chain and
cause serious damage.
ii. 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 crank. The larger sprockets produce lower gear ratios. Using them requires less
effort but takes you a shorter distance with each 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.
iii. Shifting the Front Derailleur:
The front derailleur, which is controlled by the left shifter, shifts the chain between
the larger and smaller chain-rings. Shifting the chain onto a smaller chain-ring makes
pedaling easier (a downshift). Shifting to a larger chain-ring makes pedaling harder
(an upshift).
iv. Which gear should I select?
4/ TECHNICAL INFORMATION