How do the screw in rear brake caliper pistons work? Since they must be screwed in manually with a spanner/jackscrew tool, how does the master cylinder push them out and the rotor disc push them back in without them being rotated?
There are a number of web sites that give a nice explanation,
I thank you for your reply & link, however my topic was not mentioned
I am sure you can do your own google search to find a more detailed answer. The screw in the caliper is to get the pads close to the rotor . Once close, the piston pushes the pads on the rotor when the brake pedal is depressed. Once the pressure is released the piston comes out just a bit, enough to allow the rotor to turn freely. As the pads wear, the screw can advance just a tiny bit each time the brakes are used, not enough to make a gross adjustment which the initial adjustment does, but enough to keep up with the wear.
The brake pads have locking pins on the back side that engage the piston so it won’t rotate. Engages the very same grooves you use to turn the piston to retract it.
Does that answer your question?
I am not familiar with your vehicle, and you did not mention the year. but if you have electronic emergency brake then you cannot screw the piston in. you will either have to go into your settings and disarm the electronic emergency brake before working on them. some vehicles do not have the option in their settings to do this and you need a special scan tool to do it.
The screw is for the parking brake and to keep the rear calipers adjusted for pad wear.
Each time the parking brake is used, this causes the screws to rotate so pistons push the pads so they come in contact the rotors.
Then when parking brake is released the pistons move away from the rotors.
Under normal braking, the pistons move by hydraulic pressure.
Tester
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thanks, Tester, you have answered the exact question I had asked