Wheel cylinder

Its function is to exert force onto the shoes so as to bring them into contact with the drum and stop the vehicle with friction.

[2] The wheel cylinders are usually connected to the shoes with small bird-beak shaped rods.

It is very similar to a slave cylinder and functions in much the same way, internally consisting of only a simple plunger.

When brake pressure is applied, the pistons are forced out, pushing the shoes into contact with the drum.

Some designs use two single piston wheel cylinders, one at the top of the drum and one at the bottom, each connected to one brake shoe.