CdaCrr

Cycling app computing aerodynamic and rolling resistance coefficients.

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

...