clicking from rear
Had the same thing on front tire this summer - sounds like hitting joint in the road -but there are no joints. Turned out to be tread separation in the tire. The faster you go the more pronounced the clicking as the tread slaps against the tire core. Only give-a-way was there was a slight bulge in tire tread about 10" long making the tire slightly out of round. Have your rear tires checked. Only suggestion I have.