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ANATOMY OF THE BIKE
Before we look at the features distinctive to each of the various types
of bikes, let's have a look at how the basic bike is assembled. A bicycle
consists of:
· The frame
· Wheels (hubs, spokes, rims, tyres)
· The transmission system (pedals, chainset, shift lever, chain,
cluster)
· Brakes
· Pedals, stem and handlebars the saddle.
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Lightness and strength are the essential qualities of a good frame, and for this reason light alloy steel tubing, aluminium or carbon fibers are the materials most often used in its construction.
WHEELS
The bicycle wheel is designed 50 as to be as light as possible. Spokes,
the fine rungs that radiate out from the hub off the wheel, provide structural
support to the rim, which holds the tyre.
Your bicycle tyre may he one of
two basic types:
A high pressure (or wired on") tyre or a single (or tubular) tyre.
The high-pressure tyre has a removable inner tube, which is easily repaired
with a simple patch. The single tyre is glued onto the rim and has the inner
tube sewn into it, and while it is generally lighter than a high-pressure
tyre it is much more difficult to repair in the event of a puncture.
The rim, which is best made from a lightweight alloy, is also of one of two basic shapes: gutter-shaped for a high-pressure tyre and dish-shaped for a single. The hub-the center of the wheel-usually has quick release levers to let you change a wheel in seconds if you puncture.
GEARS
Most bikes have multiple gears. These help you maintain an efficient pedaling
rate or "cadence" on different surfaces and gradients.
Gear ratio is determined by the size and the number of chainrings on the crankset and the size and number of sprockets or cogs on the cluster or block.
A crankset can have two to three chainrings of varying size. A front derailleur, secured to the seat tube, is the mechanism used to shift the chain from chainring to chainring. A rear derailleur, secured to the rear dropouts, moves the chain from sprocket to sprocket. The rear derailleur also keeps the chain tight by wrapping it through a spring-loaded arm.
Sprockets and chainrings are described by the number of teeth they have. A cluster may have sprockets with 13, 14, 15, 16, 17 or 18 teeth. A chainset might have two chainrings with 53 and 42 teeth. A high gear is where the chain sits on the biggest chainring and the smallest sprocket, and it is often referred to as 53 by 13 or 53 by 14. A low gear is where the chain sits on the smallest chainring and the biggest sprocket, and it may be referred to as, for example a 42 by 18 or a 42 by 17.
SHIFT LEVERS
The shift lever is the means for moving the derailleur from sprocket to
sprocket before holding it in place. It may be mounted in one of many positions
on the down tube, on the stem, on the ends of the handlebars or as a "thumb
shifter" on top of the handlebars. Recent technology has incorporated
the gearshift lever with the brake lever. A cable running from the shifter
operates the derailleur.
Shifting gears is an important skill. When shifting from one gear to another, it is important to align the derailleur so that the chain meshes smoothly with the sprocket. Feel and ear do this. If you have indexed gearing, this will automatically occur if your gears are adjusted.
CRANKSETS
Cranksets and chainrings are usually made of aluminium or steel. They vary
in design from the one-piece crank chainwheel and bottom bracket set to
cottered cranks (which are fastened to the bottom bracket axle with a wedged-shaped
pin) and to the cotterless crankset. Racing, mountain bike and touring riders
use cotterless cranksets with removable chainrings.
PEDALS
There are three basic types of pedals: cage, platform and system. Cage pedals
are fitted with toe clips. Platform pedals have a larger surface area for
supporting the foot. The most popular pedal is the system pedal, similar
to step-in ski bindings so that no toe straps or clips are needed.
BRAKES
Brakes can be of many types. The most common brakes on racing, touring and
mountain bikes are the side-pull, centre-pull, and cantilever.
HANDLEBARS
Handlebars are basically two shapes: flat or dropped. Dropped handlebars
are more suitable for racing and touring whereas flat handlebars allow the
rider to sit more upright and so are most commonly found on mountain bikes
and street bikes.
Handlebars can also have extensions such as time trial bars for time trialling, and bar ends for mountain hikes.
SADDLES
There are two basic saddle designs. The first is the mattress design, which
is wide and comfortable and often fitted with coil springs; the second is
the racing design, which is narrow at the front. This reduces rubbing on
the inside of your thighs.
Now that you know how the various bits of the standard bicycle all fit together let's have a closer look at the design features special to the different types of hikes.
