I've always used the top one on the rear calipers.



And I believe thee's other cars that require you to turn the psiton back in instead of just pressing it.

 

Its not a Mazda thing. On all rear calipers that have emergency brakes they screw in like that. Ive seen it on Saturns and Nissans. From what some mechanics have told me is that when you pull the ebrake handle the caliper screws out to squeeze the disk. This is why you have to turn them in. I mean would they sell a special tool for this in just about every auto parts store if this were just a Mazda feature?

 

all hydraulic e-brake systems seem to have the same style piston (single at least), i just looked at my dad's 97 saturn coupe and the rear piston looked the same and had to screw in, then i put a set of hawk HPS pads on the car

 

i've worked on cars that have a different setup, but the screw in piston is very common on the rear disc cars, to facilitate an integrated manual parking brake.



for example... on a crown vic that i worked on which had rear discs, it had a small drum brake integrated with the rotor for the parking brake. That made it a real bitch to get the rotors off because the shoes had worn into the rotor-drum and a nice rust ridge formed (yum, salty winters) ... reaching the adjuster through the backing plate was a pain in the *** on that car because the shoes were very small everything was a tight fit. but on that car the piston compressed normally.



my fiero had screw in stock but the wilwood setup has a seperate caliper for the parking brake that is purely mechanical.