Handleiding Burley Bicycle (pagina 15 van 27) (Engels)

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a. Shifting Gears

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).

d. Which gear should I be in?

The combination of largest rear and smallest front gears (ﬁg. 16) is for the steepest

hills. The smallest rear and largest front combination is for the greatest speed. It

is not necessary to shift gears in sequence. Instead, ﬁnd the “starting gear” which

is right for your level of ability — a gear which is hard enough for quick acceleration

the bike. Maximum braking force for each wheel occurs at the point just before the

wheel “locks up” (stops rotating) and starts to skid. Once the tire skids, you actually

lose most of your stopping force and all directional control. You need to practice slowing

and stopping smoothly without locking up a wheel. The technique is called progressive

brake modulation. Instead of jerking the brake lever to the position where you think

you’ll generate appropriate braking force, squeeze the lever, progressively increasing the

braking force. If you feel the wheel begin to lock up, release pressure just a little to keep

the wheel rotating just short of lockup. It’s important to develop a feel for the amount

of brake lever pressure required for each wheel at different speeds and on different

surfaces. To better understand this, experiment a little by walking your bike and applying

different amounts of pressure to each brake lever, until the wheel locks.

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 toward 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 descents shift 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. Tire 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 way to maintain

control on loose or wet surfaces is to go more slowly.

D. Shifting gears

Your multi-speed bicycle 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.

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

Burley Bicycle Handleiding

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