I have been having some brake issues with my 72. The left rear caliper is hanging up. I since replaced all the calipers on the car because after inspection I found all the pistons were in pretty poor shape. I bled everything out after install and it seemed to be working well until I got 20 miles up the road and the left rear hung up and was smoking like crazy. I stopped, cooled it off and got it home without incident. Any ideas out there??