2. How brakes work
The braking action of a bicycle is a function of the friction between the braking surfaces. To make sure that you have
maximum friction available, keep your wheel rims and brake pads or the disk rotor and caliper clean and free of dirt, lubricants,
or waxes 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. 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.
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