If you're one of those people who think RAGE is a bit too large for their harddrives (21,5 GB) and you don't play the multiplayer or coop, here are some good news:
If you go to the folder (or your equivelant):

You'll see there is a folder called "MP". Simply delete it (or move to another system drive if you want to save space on just the drive RAGE is installed). Bam, RAGE is now 6,8 GB less, which means it's size is now 14,7 GB instead of previously 21,5 GB.

Just a small tip. Just remember not to press "Multiplayer" in the game menu - the game will restart and hang and bad stuff will happen..