Originally Posted by
FBinNY
If you feel the clearance seems too close, check that the hanger isn't bent, and the RD cage is straight.
This^^^
Shift your bike into a gear combination that makes the derailleur arm point straight downward. Prop your bike against something so that it's standing up vertically. Now walk around and look at your derailleur from the back of the bike. If it looks like it's pointing toward the rear tire - that's it.
Cheap bike, you can probably bend it back with your hands. Quality bike you'll probably be better served by having a shop align it with a gauge. That's about a $15.00 service.