I mean smoother performance.

It don't, you just perceive the performance as smother because the images may become so.

V sync does make performance smoother in some games. Dead Island, for example.

if anything else, V sync lowers your frame rate, to sync with the screen. So the performance is not smoother (just synced together), but the visuals are.

However, as the end user, what you see on the screen is the final product, so if it looks smoother, it becomes smoother, if you know what I mean....

Tearing isn't about having too many frames to cram into your refresh rate. Its about updating the graphics during a refresh which creates a tear because you have two totally different images being drawn in the same pass. It can be even more noticeable at low FPS given that the differences between frames is more dramatic.

Very true... in that situation the only way vsync could help is if it dropped the game to 30fps (then the monitor would be showing each frame twice <.<).
That's what I was trying to say, thanks. ;)

I know V sync lowers your frame rate that is why I made this thread. :) Some games perform better with V sync on and it doesn't make sense to me. So hoping someone has an answer to why some games perform better with V sync on.

what do you mean when you say "perform better"?

Perceptual improvement seems like the most probable explanation in most cases. If I were to take a stab at actual improvement reasons I would have to theorize that a game may have a wild FPS swings depending on what all is going on. Like one second going from 120FPS down to 20FPS with a slight camera shift or addition a few character models.

By turning on V-Sync maybe you are forcing the game to not take such wild swings(20-60FPS vs 20-120) which may make the game seem visually smoother when paired with the elimination of tearing.

Another idea is when calculating the time variable that all things are relative to, it is generally necessary to use the amount of time it took to render the previous frame since you can't really predict how long it will take to do the one that is currently being worked on. If there are those sudden wild FPS swings then the timing could get thrown off a bit. Not so much you could tell what was happening, but maybe enough that you feel some roughness.

If you are really curious you can search the gamedev.net forums. I'm quite sure V-sync is a regular discussion topic. I've recently discovered that. I had been wondering why an old sprite editor I wrote years ago now emits a high pitched whine when run it. I think its because the card is trying to kill itself by giving me a ridiculous amount of FPS. Then I have something more recent I was working on that was taking less than one millisecond to render. The timer resolution was in milliseconds so it looked like it was taking zero time to render and it caused a time lock where nothing would update. To fix it I had to add a wait to the render code so time had always passed. Then there was some extra sticky stuff with the ultra low numbers but that's getting too detailed.

I had never given much thought to a high FPS causing problems, but there are some weird things that can happen. Though they are probably fairly rare, and I don't think they could cause smoothness issues unless a game was rendering faster than the system's timer resolution(and I highly doubt that.)