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Last Modified March 27, 2014 10:33 AM
Tech
Shifting gears
How brakes work
The braking action of a bicycle is a func-
tion of the friction between the braking sur
-
faces. To make sure that you have max-
imum friction available, keep your wheel
rims and brake pads or the disc rotor and
caliper clean and free of dirt, lubricants,
waxes or polishes.
Brakes are designed to control your
speed, not just to stop 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 mod
-
ulation. Instead of jerking the brake lever to
the position where you think you’ll gener
-
ate 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, experi-
ment a little by walking your bike and apply
-
ing 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 “Bicycle suspension” on
page 37). 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.
Shifting gears
Your multi-speed bicycle will have a
derailleur drivetrain (see “How a derail
-
leur drivetrain works” on page 34), an
internal gear hub drivetrain (see “How an
internal gear hub drivetrain works” on page
