When I am able to see any of the floor my FPS is around 50-60, when I move up my view enough so I cannot see the floor anymore my FPS shoots up to 99 FPS, I have V-Sync enabled and max_fps set to 100 so thats the highest it will go. I've attached some screens to show you what I mean.
This is while not looking at the ground. (99 FPS)
http://www.halflife2.net/forums/attachment.php?attachmentid=9851&stc=1
Now I stood still and tilted my view down just enough to see the ground.
This is when I move my view down so I can see the ground. (51 FPS)
http://www.halflife2.net/forums/attachment.php?attachmentid=9852&stc=1
This is while not looking at the ground. (99 FPS)
http://www.halflife2.net/forums/attachment.php?attachmentid=9851&stc=1
Now I stood still and tilted my view down just enough to see the ground.
This is when I move my view down so I can see the ground. (51 FPS)
http://www.halflife2.net/forums/attachment.php?attachmentid=9852&stc=1