Go to C:\Users\YourUserName\AppData\Local replacing YourUserName with your windows login name and create a "id software\rage" folder structure. So you end up with the following folder:
C:\Users\YourUserName\AppData\Local \id software\rage
Again replace YourUserName with your actual windows loging name.
Now when you run the game you will see 2 files in that folder FileCache000.bin and FileCacheHeader.bin. This improves performance greatly although I still see tearing even after forcing VSync with Catalyst Control Center.