Virticle sync is usually the biggest contributor to that effect. Low fps spikes are also often the cause.
Most of the other video settings such as aa and af can increace either performance or immage quality, however, will have little effect on your tearing problem.
Think of your tearing problem liek this: you and a friend are in the dark and he has a flashlight. He flashes the flashlight at you every second. However, you are sitting in the dark with your eyes closed, and you only open them every 1.5 seconds.
In that example you will only see one flash every 3 seconds even though you are both updating nearly twice as fast as 3 seconds.
When your monitor is set to have a refresh rate of 85Hz it means it completely redraws the screen 85 times per second.
If your video card is redrawing the screen faster than this - your monitor can have refreshed the top half of the screen while your video card tell sit to draw something completely different on the bottom half. If your FPS and refresh rates are off by the right value you can have many different immages drawn together causing your "tearing" effect.
This similar effect can be seen with low FPS as well although its a slightly different ordering but same idea.
I would suggest that you operate at your VSync value for a few reasons. First, MOST people (i'm not saying all) cannot discern the difference between refresh rates of 72Hz and 85Hz. So why do you need the extra frames? Second - if your monitor is only capable of outputting 85Hz then the fastest you can see clean immages is 85FPS. Anything above that will cause tearing. Infact, having FPS much higher can often cause the tearing to be worse.
This is why monitors ARE an essential part of a computer build - because they indirectly affect your playable FPS. Also note that with LCD monitors is can become more complicated as you then have to take into account responce time which is in mS - but CRT's redraw on their refreshes where as LCD's update on their refreshes - so LCD's do have a more solid immage.
So anyways, I hope any of that was usefull to you. Figured I'd throw my cents into the barrel while I was stopping by and noticed an unanswered question.
