rear brakes get too hot

I have noticed after driving several miles with just normal braking no panic stops the rear brake drums are too hot to touch . backed off the adjusters no change. The car(s) is a 69 Barracuda with front power k/h disc rear drums 8 3/4 suregrip rear . I have also noticed same thing on my 67 cuda with drums front and rear 7 1/4 rear. After driving home from work 27 miles rear drums too hot to touch front drums warm, also checked my Ranger after a drive home from work rear drums only warm. Any ideas , anyone else experienced the same thing ?