pulling to the right

#4
4. Backing plates worn where the shoes ride

...is insidious. Everything looks OK, backing plates might show wear, but the shoes bind against the backing plate. This happens even if the 'pads' where the shoes rub are lubricated.

It took me a LONG time to figure this out.
Symptoms include: works sort of OK, until you brake hard and you hear a 'clunk' sound.. The shoes move against the backing plate and then the brake gets grabby and won't release as well as it should. Once the shoes move around a bit the grabbiness goes away. This happens because where the shoe rubs against the backing plate, there is a small notch worn into the backing plate.

I finally took a sander and 100 grit paper to smooth out the 'pads' (raised portions on the backing plate). Now that side works nicely. Must do it to the other side.

I believe the effect is worst on the "leading shoe", as that is the one which moves out more and self-energizes. (Self-energizes means, the shoe moves out, and the friction against the drum causes it to pivot a bit and force itself harder into the drum.)

When the wheel cylinder is at the top as on these cars, it is the shoe facing the front of the car that is the "leading shoe", the one that uses that leverage to add braking force.

Drum brakes are subtle, amazing feats of engineering.