[ewgoforth]

Leading shoes on drum brakes were self-energizing like the old Pedersen mountain bike brakes. With a leading shoe the pivot point is after the braking surface, so the friction tends to push the shoe harder against the drum. Most drum brakes had one leading and one trailing shoe.

Some motorcycles even twin leading shoes on the front (maybe even four leading shoes with two sided drum brakes). These had issues with modulation like the Pederson brakes. You also had twin trailing shoes when backing up, so you had to squeeze the brakes extra hard then.