From here: http://www.justanswer.com/questions/1g9ge-why-would-my-rear-rim-be-hot-to-touch-after-driving-2-hrs-on
The picture doesn't seem to work. Go to the link. They have a picture of exactly what I was talking about.
I’ve seen rear disk brakes with drum parking brakes in the middle on Mercedes-Benz cars and also on a ‘75 Imperial with rear discs.