My car has disc brakes in the rear, and the calipers have a small lever, which is pulled by the parking brake cable. (The parking brake uses the discs, so there is no additional drum or similar.)

When resetting the pistons, they also have to be rotated (clockwise in my case).

This system is quite common for many car models, but I would like to know how this works internally, so can anyone describe it or has some good references?

2 Answers 2


The operation is simpler then you might think. In broad strokes there is a screw type setup in the center of the piston. One part of the screw is loosely attached to the piston, the other part is attached to the lever. When the breaks are applied using hydraulics the piston has some degree of freedom to move beyond the length of the screw setup. If the piston moves farther then the screw will allow the screw will rotate slightly to accommodate, this happens as the pads wear. To bring it all around, when the lever on the back is pulled it rotates the screw extending it. That extension pushes out on the piston activating the breaks.


The general answer to the title of your question is that in cars with rear disc brakes, the parking brake either actuates the disc calipers (usually with much less force) or has a small drum brake housed within the hub assembly. As an example of the latter, Subaru's have a small drum brake within the hub that works against the inside of the disc rotor which sits over the hub.

I suggest you state which model of vehicle you have if you're looking to understand how a specific part works.

  • As said in my question, I'm interested in the version without additional drums, which actuates the calipers. Those need the special treatment when resetting. The system is quite common, and I'm interested in a common answer. But if it helps: Kia Picanto 2008.
    – sweber
    Oct 3, 2015 at 11:16

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