But the vsync rate is still 60Hz, so if you don't display 60 different frames each second you are not going to get smooth motion. If you generate 58 fps with an even spacing you will get a noticeable 2Hz alias signal because every 30 frames you will get a duplicate rather than a new frame. In practice there will probably be enough jitter in the 58 Hz signal that the alias will become noisy and will be less noticeable.