23
the brake quick release works on your bike and check each time to make sure both brakes work
correctly before you get on the bike.
2. How brakes work
The braking action of a bicycle is a function of the friction between the brake surfaces — usually the
brake pads and the wheel rim. To make sure that you have maximum friction available, keep your
wheel rims and brake pads 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 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.
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 to begin with.
D. Shifting gears
Your bicycle has a deraileur drive train.
1. How a derailleur drive train works
If your bicycle has a deraileur drive train, the gear-changing mechanism will have:
• a rear cassette or freewheel sprocket cluster
• a rear deraileur
• usually a front deraileur
• one or two shifters
• one, two or three front sprockets called chain rings
