Minor correction. The late model E320 (1993-95) did indeed have the same diameter rear rotor (278mm) as the 400E/500E, but with solid (9mm) discs intstead of vented (24mm). However the early 124's (1986-92, approximately, and ALL diesels) had smaller 258x9 rear rotors - except the 1990-up coupe, which got the 278x9's.
Basically any 24-valve engine got bigger brakes (front and rear). The brake size from the factory was directly related to engine power output, that's why the 93-up E320 got the upgrade, because power jumped from ~177hp to something like 217hp. The coupe had the M104 engine before the sedan, hence the different year for the brake up-sizing. The ONLY cars that had vented rear rotors were the M119-powered models - 400E/500E.
Confused yet?
