Hi-Ya Laura,
Long time no see!!!!
Your brake shoe wear pattern is entirely normal.
Here is why:
Passenger car drum brakes since at least the early 1950s have been of the "self-servo" persuasion. In the "self-servo" design, when the brakes are applied, the leading (forward) brake shoe moves into contact with the rotating brake drum. The entire brake shoe assembly (both shoes and misc. hardware) then pivots rearward from the top and "wedge" the trailing (rear) rear brake shoe into the rotating brake drum.
Have you noticed that the brake shoes and connecting hardware are not solidly attached at the bottom of the backing plate? That is a deliberate design feature. It allows the entire brake shoe assembly the limited amount of play required to pivot.
The idea underlying the "self-servo" design is that the "wedging" (not to be confused with a "wedgie" :twisted: ) action multiplies the braking force applied by the driver and makes for lower brake pedal pressures required to stop a moving vehicle. That became an important ergonomic design consideration as the cars of the early fifties went on steroids and became larger and larger and heavier and heavier and faster and faster - increasing brake system loading.
Keep in mind that vacuum-assisted power brakes were not available or available only as a high-cost option on many cars of the period.
It is inherent to the "self-servo' design that the trailing brake shoe actually provides most of the stopping power. Hence, the trailing brake shoe will wear faster than the leading brake shoe, and that is also why there is more brake pad material on the trailing shoe? (A way to tell them apart.)
(A related aside: the self-servo design is also why your brakes seem to not work as well when the vehicle is moving backward. It seems that way because it is true.)
Entirely unrelated, but it seems a good time to remind everyone that white eggs come from white feathered chickens and brown eggs come from brown or red feathered chickens. :wink:
I hope that helps.
Best regards,
Gadget
PS: Related to the above is a process called "arcing" brake shoes. In brake specialty shops, you will usually find a machine that is used to "arc" new brake shoes. Brake shoes need to be arced after a brake drum is turned on a lathe. The inner diameter of the drum changes, becoing larger, after lathing. Hence, the brake shoes need to be arced to match the new diameter of the drum to provide optimal frictional contact. Failing to arc new brake shoes to match a turned brake drum is why a brake shoe will initially wear faster in the middle of the shoe then at the ends of the same shoe.
Here is an illustration to perhaps better explain why new brake shoes should be arced to match a turned brake drum. NB: I have greatly exaggerated the effect for the purpose of illustration.
Shade tree mechanics ignore the arcing process, but for a "pro" brake job, arcing really should be done.
