Yes, you need the tool that rotates the piston on the rear. Not necessary on front.

 

Does anyone have a vid or some kind of elaboration? The Mustang is the only car I have heard of this.

 

Most cars that have rear disc brakes that also incorporate the parking brake in the same caliper require the piston be rotated back to the retracted position with a special tool. The parking brake uses a threaded shaft in the center of the piston that auto rachets the piston out as the pads wear when the parking brake is applied and/or as pads wear.

BD

 

I found this on that other Mustang forum

Ford Mustang Rear Disc Brake Pads Replacement Guide - 2015, 2016, 2017, 2018, 2019, 2020, 2021 & 2022 - Picture Illustrated Automotive Maintenance DIY Instructions

How to change the rear disc brake pads on a sixth generation 2015, 2016, 2017, 2018, 2019, 2020, 2021 and 2022 Ford Mustang EcoBoost 2.3L I4 model with photo illustrated steps and the compatible replacement part numbers.

www.paulstravelpictures.com

 

I found this on that other Mustang forum
Ford Mustang Rear Disc Brake Pads Replacement Guide - 2015, 2016, 2017, 2018, 2019, 2020, 2021 & 2022 - Picture Illustrated Automotive Maintenance DIY Instructions