J55 & C5 brakes are both 13" rotors with dual piston calipers, but that is about where the similarities end - no parts are interchangable.
The C5 rotors are about twice as thick as the J55's. The C5 caliper is also a bit heavier duty and is a bolt in design unlike the J55's quick change pin style. Also that pad surface is bigger with the C5s.
The C5 rotors are about twice as thick as the J55's. The C5 caliper is also a bit heavier duty and is a bolt in design unlike the J55's quick change pin style. Also that pad surface is bigger with the C5s.