Why do I have to finish a CHALLENGE ride within a radius of 5 km / 3.1 mi from my starting point?

Wind direction and wind strength cannot be included in the calculation due to a lack of data sources. Therefore, each CHALLENGE ride...

Wind direction and wind strength cannot be included in the calculation due to a lack of data sources. Therefore, each CHALLENGE ride must be finished within a finish radius (5 km / 3.1 mi) from the starting point of the ride. This ensures that the ride is driven with and against the wind (loop).