[RobRoy]

Some cars use completely separate pads for the emergency brakes. My old LeBaron had disc brakes in the rear but inside they had small drum brakes as the emergency brakes. I know it probably doesn’t matter, but unless you’re just locking up of the wheels, it would give more grab.

[my right]

I'll have to say I have never seen both disk and drum brakes on the same wheel. Usually the emergency brake is controlled by a cable and the brakes are activated by hydraulics, but both are activating the same shoe or pad.