According to the parts manual, there is only a lower centering block that holds the two lower shoes points. Usually there is a manual adjuster on drum brakes that the part brake or self adjusting mechanism click into and automatically adjusts up the opposite end of the shoes from the wheel cylinder.
I don't see anything in the parts breakdown that looks like a self adjuster.
Also as others have said, because of the way the cylinder pushes out and operates in series the two shoes, they are self-energizing. A lot like strap brakes on the old cars with a leather strap. The strap works best with one direction of the drum versus the opposite direction. The shoes do the same in that the more they push out the more the brake drum friction grips harder and "adds" pressure to the shoes against the drums.
I'm still at a loss though on what keeps the shoes out within first striking distance of the drums.
You "should" be able to adjust the lower centering block to re-arc the shoes, so to speak to the diameter of the drum. Maybe the park brake has a part in this adjustment. But that would eventually get you out of park brake pull on the lever if you didn't readjust the cable periodically as normal maintenance.
Drums should "just" slide on over the shoes when properly adjusted. There will be some drag until they seat into place.
I also didn't see any residual valves in the plumbing pages. Usually with lower mounted master cylinders, they use a 2psi on the front for rotors and a 10psi on the rear for drums. The residual valve hold that amount of pressure in the line against the wheel cylinders do they don't retract as far from the rotors/drums. Without residual valves, sometimes you have to pump the pedal too far to get the first bit of braking force.
I used them on several of my street rods with lower frame mounted master cylinders.
So I'm not sure what MMC uses to hold the pads and shoes close to the friction points.
Good luck with your swap out on your next tire change.
I'm used to seeing disc pads about 6mm to 8mm thick, but on my new Harley with disc and ABS, the pads are only about 2mm to 3mm thick. I thought they were worn out until I saw a new set at the stealership.
