[John Brown]

Buick was 5" on the big cars until about 1978 when some of them started using 4 3/4", the A bodys were 4 3/4" as long as I can remember. We used to have to know what diameter rear drums the 78 and later cars had to know what bolt circle front rotors to sent to our customers. 9 1/2" rear shoes meant 4 3/4" b.c., 11" rear shoes meant 5" b.c.