Setting up your turbo trainer and bike for Virtual Watts
To capture the speed of your rear wheel you will need to mount an ANT+ or Bluetooth speed sensor to the non-driveside chainstay of your bike and a magnet to the spokes of your rear wheel. There are many popular brands and models of speed and cadence sensors, such as those from Wahoo and a full list of supported sensors can be found in our Compatible Sensors article. (Note that iOS is Bluetooth only. For more information about using ANT+ sensors in iOS, please check this article out: Connecting ANT+ Sensors
Install the sensors and pair it to the app (provided you have the right ANT+/Bluetooth connectivity).
Many sensors have adjustable arms so that the sensor can be moved as close as possible to the magnet. Where possible, we recommend the arm pointing south/hidden behind the chainstays so that it's less likely to catch or obstruct anything.
You can also buy one of the newer hub sensors. This device from Wahoo wraps around the rear hub of your bicycle wheel. This makes for a cleaner setup and gets rid of the need to make sure magnets and sensors are properly aligned. The hub sensor automatically tracks RPM from the hub.
What else do I need to know?
Training with power works best when the power data is consistent from workout to workout. The rolling resistance is the factor that will determine this consistency. There are two key things that you can do to keep your rolling resistance consistent and your Virtual Watts accurate over time:
- Keep your tyre pressure consistent. If your tyres were at 90 psi for your FTP test, make sure your tyre pressure remains as close to 90 psi. This is done best using a pump with a pressure gauge.
- Keep your 'trainer pressure' consistent. Trainer pressure refers to the contact between the turbo trainer and the rear tyre. To achieve consistent trainer pressure, make sure you adjust the 'roller' equally every time you install in the bike on the trainer.