I'm building a replica of a 1932 Studebaker Indy race car. The front brakes are circa 1967 Riviera with 2-1/4" wide shoes, the back ones are 1961 Buick Invicta backing plates with 2" wide shoes. I've got the Buick 12", 90-fin front drums on all four wheels. As I was mounting the rear brake shoes the other day, it occurred to me that the drums are about 1/4" wider than the shoes in the back. Will the shoes stay where they belong or have I created a problem? I don't think shoes ever rub on the sides of a drum, but what keeps them against the backing plate? The 2-piece hubs take wire wheels with knock-off centers.
What you have there in terms of backing plates, shoes and drums is very similar to what’s on the front of my avatar. I run 90 fin drums with 2” wide shoes on old F2 backing plates. What holds them in place are the various springs and retainer pins as shown in your photos. I chose the 2 inch shoes because that’s what the backing plates used. I am thinking different width shoes would require at least a different top centering pin as well as the retainer pins. Someone will know that for sure. Nice looking car there.
The two hold down springs and pins keep the shoes against the backing plate. The other springs are return springs and draw the shoes back against the large pin at the top of the backing plate the hold down springs and pins are designed to allow the Bendix style shoes to float but keep them drawn against the backing plates. All Bendix single or dual servo brakes are retained in the same manner.
I may have just answered my own question. I think the two pins and dinky hold-down springs with cups will hold the shoes against the backing plate when the brakes aren't energized, but I'd be suspicious that they can't do that when the wheel cylinder pushes on the shoes and large forces are developed. However, there is the plate with the two ears (anchor shoe guide) that holds the top of the shoes against the backing plate at the centering tube/anchor. The return springs hold the guide plate in place. So, at least one end of the shoes stays tight against the backing plate. I assume (always dangerous!) that the cylindrical shape of the drum and shoes will keep the rest of the shoe where it belongs, helped a little by the small hold-down springs. I'll find out when I finally get it all together!
I cant see in your pic, but you have the bottom spring over the adjuster, right? If so, you aren't missing anything.
Keep in mind that the shoes only move a small amount, so everything stays in place very well. Look at the system with the drum off, gives us the impression that quite a bit of movement takes place. It is captive in a small area when all assembled.
I agree with @alchemy , I think there is usually a spring across the bottom to hold the star wheel adjuster mechanism in place, even with manually adjusted brakes.
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