Bit of a rant about single-piston calipers used on mid-sized and big Mopars

Don't 95% of new cars today use that same single-piston, sliding caliper design? In contrast, 1964-72 A's had fixed 4-piston calipers (as did Mustangs), as do many high-end sports cars today. It does seem unreliable that the square O-ring is supposed to rotate and act like a spring to retract the piston, but seems to work well. Post 5 is the first I read of a trapezoidal groove, but that helps it make sense. If your calipers are old, the O-ring may be too stiff. On most cars, rebuilt calipers are so cheap that most people go that route. I rebuilt the calipers on my 1982 Aries, because rebuilt ones were probably expensive then. That might make sense on a 1970's Mopar. The only trick was getting the piston started without cocking in the bore.