According to the LG specs, the native refresh is 60. The width is 2560, which can be a turning point in performance for some cards--anything higher and you may have strange results (depends on your hardware). With your GPU/Monitor setup it may be possible to override it to 75 with more "normal" output, but something more involved may need to be scaled back to 60 for quality purposes.

Are you running with V-synch disabled in Windows? This can sometimes lead to tearing as well. If so, try locking the v-synch and enabling triple buffering. If that doesn't resolve it, then try lowering the refresh in Windows to 60...may need to lock v-synch (or use adaptive) as well.