About this app

Bike computer to ride faster by improving your aerodynamic position and testing gear/equipment. Among other data, it monitors CdA (drag*area) and Crr (rolling resistance) coefficients, during races or dedicated testing sessions. It requires BLE or ANT+ power and speed sensors, and an anemometer (option, see below) for improved precision.
Powermeters successfully tested are:
-Power2Max
-Assioma pedals
-PowerTap hub (records speed so additional sensor is not needed)
Speed sensors currently supported are:
-CycleOps
-Garmin (Warning: old Ant+ Garmin model is not working with the app)
-Wahoo
-CooSpo

Avoid any magnet less speed sensor, their accuracy is not as good.

Read the help to quickly see how to use the app: http://cdacrr.blogspot.fr/p/help.html

If you need help, you may post on Slowtwitch forum, on this thread .

Current features:
-Compare Crr between different tires on ridden laps at slow speed (<15km/h)
-Compare your CdA between different positions on ridden laps at high speed (>25km/h)
-Configurable field to switch between different fields (altitude, cadence, bike direction,...)
-Model uses air density accuratly computed with weather station data and detected sensors
-One FIT file and several CSV files are stored and can be sent by mail for post analysis
-Hear/record voice message each lap
-Activate cloud storage to list/edit previous runs later
-Plot virtual vs real elevation (barometer needed)
-Measure road vibration with phone accelerometer if available
-Wind forecast on location where you plan to field test
-Enable/disable auto-zero feature of ANT+ powermeter

The app is free, but more features are available with the premium version:
Premium features:
It includes other modes (described here):
-Defined lap length mode (for velodrome, click once to start the run)
-Time trial mode (needs barometer) to get CdA at the end of the race
-Criterium mode to get apparent CdA lap per lap during a race
-Training mode
And some optional devices:
-Support Weather Meter anemometer to record air speed (to get higher precision for CdA numbers during windy days)
-Possible to use Bluetooth headset to hear/record voice messages (useful during velodrome testing)

Download the key for the premium version here

Known bugs/possible issues:
-BLE connection with older phones is sometimes tricky
-Random ANT+ dropouts
...

New features

See here: https://cdacrr.blogspot.com/p/release-notes.html

App Permissions

Allows applications to connect to paired bluetooth devices.
Allows applications to discover and pair bluetooth devices.
Allows access to the vibrator.
Allows an application to write to external storage.
Allows an application to read from external storage.
Allows an application to receive the ACTION_BOOT_COMPLETED that is broadcast after the system finishes booting.
Allows applications to open network sockets.
Allows applications to access information about networks.
Allows an app to access precise location.
Allows an app to access approximate location.
Allows an application to record audio.
Allows an application to broadcast sticky intents.
Allows an application to modify global audio settings.
Allows using PowerManager WakeLocks to keep processor from sleeping or screen from dimming.