I have a tacX trainer and zwift on my laptop. During a regular route on watopia or one of the locations the speed is accurate, I use the trainer instead of speed sensor. BUT during a training program or a free ride in the training program the speed is not accurate. Power is consistent but not the speed. Anyone else have this happen? Thanks!
Please read this: https://forums.zwift.com/t/how-does-zwift-determine-my-speed/