Copyright Velocomp LLP 2008-2017
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For the first 4.4 miles of this ride the rider had CdA measurements that, most often, were
above his normal value of 0.39.
A higher-than-normal CdA means the rider was relatively
less aerodynamic, and that he lost time due to his relatively poor riding position
. How
much time did his high CdA cost him? According to the graph, the time lost peaked at -42
seconds at mile 4.4. What does negative 42 seconds mean? It means that if the rider had
pedaled equally hard,
but had always stayed in his normal ride position
, then he would
have arrived at mile 4.4 about 42 seconds sooner. Said differently: at mile 4.4,
aerodynamic riding inefficiencies has cost this rider about 42 seconds compared to his
normal riding position.
At mile 4.4 the rider improves his riding position (becoming more “aero”) and his CdA
drops below his baseline value.
He reverses his negative Time Advantage and picks up a
lot of time
. In fact, by mile 5.2 the rider is nearly back to zero Time Advantage—meaning
that he is “on pace” compared to his normal riding position.
Between miles 6 and 8 there are some high CdA spikes but the Time Advantage curve does
not react accordingly (a high CdA should cause Time Advantage to go more negative).
Why does Time Advantage not move?
Time Advantage measurements become less
accurate as bike speed and wind speed drop
. Accordingly, the Newton does not record
changes in Time Advantage when bike speed is below 15 mph or when net opposing wind
speed is below 5 mph (caused typically by tailwinds). In this example, the rider is just
below the 15 mph threshold between miles 6 and 7, and there also appears to be a tailwind
too, causing wind speed to drop below 5 mph (we can’t tell this from the graph). Time
Advantage does NOT change between miles 6 and 8 because the Newton is operating below
its minimum measurement threshold.
Just after mile 8 the rider goes into a tuck and his bike speed increases to nearly 30 mph.
The rider gains a tremendous amount of Time Advantage: between mile 9.5 and 10 he
gains about 35 seconds
! The faster you’re riding, the more Time Advantage you get from a
more “aero” riding position.
The rider continues the tuck until about mile 11.5. At this point he has gained 50 seconds
overall since the beginning of the ride.
Between mile 11.5 and 16 his Time Advantage remains flat at about 50 seconds. This is
due to low bike speeds of around 10 mph, a result of hill climbs.
At low bike speeds,
aerodynamic forces don’t affect Time Advantage significantly.
At mile 16 the rider goes into an aggressive tuck and really picks up the pace, too.
Between mile 16 and 29 he picks up an ADDITIONAL 150 seconds of time advantage, and
by the end of the ride his total time advantage is about 200 seconds.
What does 200 seconds of Time Advantage mean?
It means that he finished his ride
200 seconds (3 minutes, 20 seconds) SOONER than he would have had he ridden
in his normal riding position for the entire ride!
Using a PowerPod or Newton gives this rider feedback about the quality of his riding
position (Continuous CdA), AND quantifies the Time Advantage of his aerodynamic
improvements.
