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How fast you finish the cycling portion of a race depends on the power
you’re able to produce during the ride. Ultimately, power output
depends on just two variables: force and speed. Very simply, it
depends on how hard you push and how fast you pedal. The three forces
you need to overcome to move forward are air resistance, rolling
resistance, and, on climbs, gravity. Because gravity and rolling
resistance depend on weight, most cyclists try to minimize weight.
This is most easily achieved by using a lighter bike and componentry,
but these come at a high cost. Rolling resistance also depends on the
road surface, as well as the make, thickness, and pressure of your
tires. The biggest resistive force, however, is air resistance, which
is dependent on your speed and frontal surface area. At 20 miles per
hour on a flat road (gravity is zero), rolling resistance makes up
less than 25 percent of the total resistance, while air resistance
makes up more than 75 percent. The most effective way to reduce air
resistance is to draft behind (or even next to) another rider. For a
triathlete without the option to draft (drafting is not permitted in
most amateur triathlon racing), reducing frontal area has the
greatest effect on performance. Aerodynamic equipment--such as bike
frames with tear-shaped tubes, deep-dish wheels and discs, narrow
water bottles, tight skin suits, and streamlined helmets--can reduce
some of the frontal area. However, a rider’s body is by far the
biggest obstacle. Bike fit for a triathlete is therefore optimized
with biomechanical....
http://mytriathlontraining.com/content/aerodynamics-and-bike-fit-speed |
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