Wheels
There are as many variations of bicycle wheels as
there are bicycles. The most common sizes are 26in,
27in and 700c. These sizes fit the design of the
diamond frame and are large enough to absorb road
surface irregularities. They also provide a balanced
feel to steering which is usually lacking in the case
of smaller wheels.
Whatever its size, the strength of a wheel is
dependent on the number and tension of the spokes. An
expertly built wheel shouldn't go out of true under
normal circumstances, although an occasional turn of
the spoke key will ensure that the spokes stay tight.
Time trial racing wheels
Minimum air disturbance is the priority. Aero wheels,
so called as they have an aerodynamic shape, have a
pointed profile that cuts through the air. They are
made from aluminum or carbon fiber and often have
spokes with a bladed profile to help increase
aerodynamics. They are expensive wheels.
Massed start racing wheels
Road racing wheels are stronger than time trial
wheels as they are likely to be ridden over drain
covers and potholes. In most cases they have 32 spokes
- although an extra four spokes is preferable for
riders weighing over 200 lb (90kg). Rims are almost
always aluminum.
Touring wheels
Reliability is everything. The heavy loads and poorly
surfaced roads encountered on a tour require stronger
wheels than those for racing. MTB 26in and 700c wheels
are popular for touring. Traditionalists go for 36
spoke wheels and box section rims.
MTB racing wheels
These have lighter rims and thinner spokes than those
used for touring. A 32-spoke wheel is light and
strong. A 36-hole rim is used for downhill racing
where strength is more important than low weight.
Spokes
Spokes are arranged in a crossed pattern. The most
popular pattern for spoking is 'three cross' - each
spoke is crossed by three others. Radial spoking
(where no spokes cross over), saves a few grams but is
prone to loosening and puts a strain on the hub
flange.
Tyre treads
A tyre with tread creates friction to maintain grip.
This is valuable in wet conditions and is beneficial
to tourists and recreational cyclists. The smooth
surface on competition tyres gives a lower rolling
resistance than a tyre with a tread. But it's a
straightforward trade off: less rolling resistance
means less grip.
Mountain bikes are often supplied with a knobbly
tread. If you do most of your riding on the road,
changing these for a smooth tread tyre will
significantly lower the rolling resistance of the
bike. A set of slick tyres is the best upgrade you can
make to an MTB for road use.
Hard or soft compounds
Soft rubber works better than hard compounds in the
wet. Dual compound treads are popular on road bikes.
They have a hard compound center tread for longevity
and a softer compound on the tyre's edge for
cornering.
Soft rubber tyres work well off-road too. They are
most suitable for riding on wet grass and slippery
rocks where hard rubber can cause sudden slides.
Kevlar, the material used for bullet-proof vests, is
also employed in puncture-resistant tyres. It resists
intrusions for longer than other materials so the
intrusion is less likely to pierce the casing. Kevlar
is also used on the sidewall to resist tearing.
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