Virtual speed is a difficult feature to explain. The necessity of implementing Virtual Speed in the Tacx applications and third party applications are basically coming from the limitations of an indoor trainer compared to the wide landscape and/or performance range of riding outside.
Every indoor trainer has its own specifications (e.g. maximum slope, maximum power, inertia). Amongst indoor trainers there are many differences, e.g. a T2180 Vortex Smart has a maximum slope of 7% and a T2800 NEO Smart a maximum slope of 25%.
It is understandable that when the cyclist is simulating the Mont Ventoux with a maximum gradient of 11%, that this can be complicated for a T2180 Vortex Smart. In order to solve this Virtual Speed is developed.
Virtual Speed is that the application being used is displaying a different speed (Virtual Speed) compared to the actual speed of the rear wheel, in the situation where the track being simulated is outperforming the indoor trainer. The difference in speed is based on a calculation taking all performance and resistance factors in account (e.g. gradient, speed, inertia, air resistance etc.). This allows the cyclist to simulate a track that is outperforming his indoor trainer.
Trainer being used is a T2180 Vortex Smart
- 25 km/h on a 1% slope, speed shown in the app is also 25 km/h (in breaking zone)
- 25 km/h on a 5% slope, speed shown in the app is 20 km (out the brake zone)
- 15 km/h on a 9% slope, speed shown in the app is 5 km/h* (Virtual Speed)
* This is an example, actual speed could be different in the application
Note: The maximum percentage gradient is calculated with a body weight of 75kg in reference to the strength of the resistance unit with a speed of 10km/h
Note: Virtual Speed is being calculated in the application. Not all applications are provided with this feature
Ascending and descending
Virtual Speed applies to ascending, but also to descending. When the cyclist is riding downhill, the rear wheel maybe only have a speed of 10 km/h (6 mi/h), but the Virtual Speed is showing 60 km/h (37 mi/h).
Accelerate and decelerate
When accelerating and decelerating on an indoor trainer there could be a difference between the actual acceleration on your indoor trainer compared to a similar situation riding outside using the same accelerating force. This is dependent on the inertia of the flywheel and the current speed the cyclist is cycling with. Also to cancel out these inequalities Virtual Speed is being used in the application (The Virtual Speed slowly accelerates when you start from 0 to 25 km/h on a trainer that is not able to simulate inertia correct).
Note: The T2800 NEO Smart is designed with a Virtual Flywheel with a very large controllable mass inertia, meaning that the NEO Smart is able to simulate at different speeds realistic inertia effect. Virtual Speed in combination with a NEO Smart is hardly being used
Handlebar computers and watches
Smart trainers can also be connected to watches and handlebar computers, showing power, cadence and speed. Due to the lack of the Virtual Speed feature in these devices a difference in speed reading is possible when comparing the applications with another device.
ERG training (power based training, Watt, FTP, HR):
Speed is not important in these trainings. In the background the program needs to understand what the distance for calculation so it just takes an average speed. If you ride faster it needs to correct the Virtual Speed. It will always be Virtual Speed in the program. This also counts for the NEO.