iBike Gen III Operating Instructions Manual page 31

"COAST DOWN" PROCEDURE
When you ride at high speed the effects of wind, bike aerodynamics, and riding
position become very significant. These effects are measured by aerodynamic drag,
commonly called CdA.
In the Fast Start sequence estimates your CdA. The estimates of CdA made by the iBike
are the result of considerable testing and experience. For 99% of riders, estimated CdA and
Crr provide both consistent and very accurate results under a wide variety of cycling
conditions.
If you do solo rides on the flats at speeds consistently above 22 mph, or you want to
measure your CdA (and, optionally Crr), then the coast down procedure is an advanced
feature that is available.
The coast down calibration found in the User sequence measures the aerodynamic (and
optionally, friction) drag coefficients that are particular to each cyclist, riding position, bike
type, tires, and road type. These drag coefficients are stored in the iBike's memory (in a
Profile) and are used in power calculations.
The coast down procedure is this: accelerate to 20 mph (32 kph), then stop pedaling. Your
bike will slow due to aerodynamic and frictional drag (your bike may also slow due to the
effect of hill slope, but the iBike factors hill slope effects into its calculations). Once you
slow to 8 mph (13 kph) the coast down is complete. For much better accuracy, repeat the
coast down 5-8 times, then analyze your results in the iBike software to get the best
composite measurements.
The Coast Down measurement works very well when its steps are followed carefully.
However, if the procedure is not followed EXACTLY, then it is likely that your iBike will be
more poorly calibrated than it was prior to the Coast Downs! So, if you decide to do coast
downs, please read the instructions carefully and follow them exactly.
Here is the Coast Down procedure:
1. Before doing Coast Downs you MUST complete the Fast Start sequence AND
the Calibration Ride.
2. Wear the clothing, bike helmet, and shoes you're going to use during your rides.
3. Find a fairly level to uphill road, with few cars, where you can coast on the road
for about 1/4 mile, without stopping, hitting big bumps in the road, making sharp
turns, or being subjected to wind gusts caused by passing traffic or other cyclists.
NOTE: THE ROAD MUST BE MOSTLY LEVEL TO SLIGHTLY UPHILL. IF THE ROAD HAS TOO
MUCH DOWNHILL YOU WON'T SLOW TO 8 MPH!
4. Just before starting your Coast Down, enter Setup, then scroll to USER. If "USER
YES" is shown, click the up arrow to enter the user sequence. If "USER NO" is
shown, click the center button (to make the word "NO" flash), then select YES with
the up arrow, then click the center button to accept ("USER YES"). Then, click the
up arrow to enter the User sequence.
5. In the User sequence, click the up arrow button until you find the "Coast" menu.
You will see the word "Coast" in the bottom window.
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