On Open Road, we use our Virtual Speed technology as the default way to calculate the speed for power meters and smart trainers. We have based Virtual Speed on the laws of physics. Therefore, it is extremely accurate. It calculates the speed from your weight, the weight of your bike, the gradient of the road, your watt output, and air resistance.
We created Virtual Speed because the speed output from your smart trainer is not always accurate. This is simply because of the limitations of the brake in your smart trainer. A good smart trainer has a brake that can simulate gradients up to 20 percent and more. Cheaper smart trainers have a brake that can only simulate single-digit gradients. Some trainers cannot simulate negative gradients.
If a route exceeds the range of gradients that your smart trainer can simulate, the trainer’s speed output will no longer be accurate. For example, if you are riding a 15 percent slope and your trainer can only simulate a slope of 8 percent then your trainer’s speed will be inaccurate above 8 percent and you will be able to ride faster compared to what would be possible on the real road. Uploading this kind of ride to Strava will corrupt the leaderboard. Likewise, if your smart trainer cannot simulate descends then you will feel you have to pedal as if you were riding on a flat road. Virtual Speed solves this problem too and corrects the speed in accordance with what it would be like descending with a real bike. As Virtual Speed is not based on the limitations of your trainer’s brake, it will make the speed from smart trainers with different capabilities comparable.
Virtual Speed is turned on by default. When it is turned on, it takes over the speed calculation completely, not only when you go beyond the capabilities of your smart trainer. If you want to use the speed output from your trainer, you can turn Virtual Speed off in ‘General Settings’ and use the speed of your trainer instead (not recommended):