The "forward" shoe is the one towards the front of the vehicle. Ron is
correct, it should be longer, and I think I know why. The wheel
cylinder is at the top on the jeep, and forces the top of each shoe
outward when the brakes are applied. Assuming the vehicle is travelling
forward (which it is most of the time), the friction force on the front
shoe will tend to pull that shoe tighter into the drum. The friction
force on the rear shoe will tend to push it away from the drum. The
front shoe is said to be "self-energizing" in this case. As a result,
the front shoe generates a majority of the brake force, and also would
tend to wear faster. The designers attempted to compensate for the
faster wear by increasing the area of the front shoe. In this way,
hopefully both shoes will wear at approximately the same rate in term of
thickness of the lining. Make sense?
By the way, some fancy cars have two wheel cylinders per wheel. The top
one actuates the front shoe, and the bottom one actuates the rear shoe.
In this way, all the shoes can be made to be "self-energizing"...
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