Stuttering with vsync on a powerful hardware

Any idea why it works this way
I have 240hz screen and I limit the games speed to 60fps(I don't see much difference at above 60fps or maybe because I have never played at above 60fps before(on my old weaker laptop))
If vsync is enabled,I have random stuttering\fps drops on any game(no matter the settings)and if it is not enabled,I have solid 60fps.
So why is that?

Open Nvidia Control Panel > Manage 3D settings > Global Settings Tab.
In that section waft your mouse pointer over Feature: Vertical sync, and read the notes that appear below, Description and Typical usage scenarios.