PERSONALISED CYCLING
PERFORMANCE ANALYSIS
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CYCLING SCIENCE |
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FORCES There are three main forces resisting motion of the bike and rider:
Only one force is available to overcome these:- •Motive force generated by the rider and transmission system |
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When the motive force exactly
equals the sum of the resistive forces the rider will travel at a constant
speed, if the motive force is greater the rider will accelerate until such a
point as the forces do equal out. |
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Rolling Resistance is a function
of rider/bike weight and the specification of the tyres. It varies very
little with bike speed, and accounts for the majority of the resistance
forces at slow speeds On flat ground at speeds above 10mph aerodynamic drag dominates.
Aerodynamic drag is determined by the rider/bike size and shape: smaller and
more streamlined is better. As the road begins to incline
gradient resistance occurs and increases with increasing steepness until it
dominates on very steep climbs. Gradient resistance is determined by
rider/bike weight |
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TRANSMISSION The
transmission system connects the cranks to the rear wheel so that the rider's
power can generate motive force to move the bike. In order to match the
riders pedalling speed to the road speed the transmission system incorporates
a step-up (for high speed) or a step down (for low speed) ratio using
different sized gears. The
transmission system is not 100% efficient; some of the rider’s power is lost
as heat in the transmission system due to friction. |
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RIDER POWER OUTPUT The
typical rider generates most power at a pedal speed (cadence) of between 90
and 110 rpm, but is most efficient (higher power:calorie
ratio) at pedal speeds of 60 to 70rpm, therefore gear selection should ensure
that pedal speeds stay within the 60 to 110rpm range at all times if
possible. A
single-speed bike can only match the rider's peak power output to one road
speed, which is why it can be very difficult to climb at slow speed on a
single-speed bike) |
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Unfortunately the human
body cannot sustain high power indefinitely; A typical rider can produce 2 to
3 times as much power for 1 minute as they can sustain for an hour. |
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The power output of a rider is determined by:- ·
The skeletal muscle system ·
The cardiovascular system ·
Energy availability ·
Levels of fatigue ·
Hydration ·
Pedalling technique ·
Riding position Shortcomings in any one of these areas will limit power output,
regardless of how well developed the other areas are, therefore training,
ride preparation and bike set-up should be designed to improve all of these
areas. |
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The steady-state motion
of a rider can be reduced to the mathematical equation shown opposite.
The coefficients of aerodynamic drag (Cd), rolling resistance (Cr) and
transmission efficiency (n) can be determined from wind tunnel and
dynamometer testing, combine these with the total rider and equipment mass
(m), plus the course gradient (θ), the rider's speed (v) and an
estimate of their frontal area (A) and we can very accurately determine the
rider's power output in watts. We
can then rearrange the equation and substitute different values of m, Cd, Cr
and Rider Power Output to determine the effect on the rider's speed (v). For
example a vented helmet and a teardrop helmet will have different Cd
values. By substituting these different Cd values into the equation we
can determine each helmet's effect on a rider's speed. |
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Laboratory studies
often show that the latest training scheme affects different people in
different ways, or two wheels with roughly the same specification perform
completely differently in practice (for example two wheels each with 50mm
deep rims may have widely different drag coefficients). Obviously
we cannot test every single item of kit on the market (although that would be
fun!), and we cannot test every individual to see how specific training
schemes affect them personally, so here at CYCLE-SPEED.COM we present the
"typical" results you would expect from each of the different types
of item tested. e.g.
if the MARGINAL GAINS CALCULATOR says you will gain 5.6 seconds from a
particular item of kit, depending on the actual product you buy, the
improvement may actually be somewhere between 3 and 8 seconds.... |
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Now
let’s see how we can use this science to improve one of your rides, click the
"Marginal Gains Calculator" button below:- |
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