On a normal car, changing brake pads is a ten-minute job: pull the caliper, push the piston back with a C-clamp, install the pads, done. On the 720S, that C-clamp is the last thing you should ever put against the piston — because the electronic parking brake (EPB) is not a mechanical lever you can overpower. It's an electric actuator, and forcing the piston back against it while the system is engaged is exactly how people damage the actuator motor. I've done caliper work on my car, and this is the complete procedure the way I run it, with the factory cross-references from the service manual.
The EPB on the 720S retracts the rear calipers with an electric motor and screw mechanism inside the caliper assembly. When the brake is applied, the motor drives the mechanism to clamp the pads against the disc. When you release it, the mechanism retracts the piston — but it retracts only as far as its own mechanism allows.
If you try to push the piston back by hand or with a C-clamp while the motor isn't in the right state, you're doing one of two bad things: either the mechanism is engaged and you're forcing the piston against a load the motor was designed to carry (binding the screw, stripping internal threads, or burning the motor), or you're pushing the piston past the point where the pads will re-seat correctly when the system re-engages. Either way, the fix for the damage is a new caliper assembly — a very different bill than the brake pads you came to change.
The solution is the same every time: put the EPB into service mode first. In service mode, the system releases the calipers and holds the actuator in the state that lets you retract the piston safely by hand. The procedure exists in the manual, and it's the one I'd never skip.
Get the car up properly — ramps or a lift, wheel off, and the caliper clear of the disc. Inspect the disc while you have it off: thickness, scoring, and any glazing. On a car that sees track days, the rear discs are the ones to measure, because the rear is where the track weight lives. If the disc is at or past minimum, it's getting replaced in the same job — you don't bed new pads on a worn disc.
Command the EPB into service mode through the diagnostic tool, following the procedure in the manual. The system will release the rear calipers and hold the actuator in the state that allows safe piston retraction. Confirm the mode is actually active before you touch the piston — some tools show the state explicitly, and that confirmation is the difference between a safe retraction and a damaged actuator. This is the step that protects the motor, so don't rush it.
With the EPB in service mode, unclip the caliper from the bracket and support it so the hose isn't under tension — you're not disconnecting the hose, just giving the caliper room. Remove the old pads and the worn hardware. This is the moment to look at the piston boot and the caliper bore for leaks or damage, because you won't get this view again until the next job.
Now — and only now — retract the piston using the correct tool, rotating it back in the direction the mechanism allows. You're working with the actuator, not against it, so the piston should move smoothly. If it's fighting you, stop and re-check the service mode state before applying more force. Force against a binding mechanism is how the actuator gets damaged, and the tool plus the service mode together are what make the retraction safe.
Fit the new pads and fresh hardware, making sure the pads seat flat and the anti-rattle clips are in place. Slide the caliper back over the pads and re-clip it to the bracket. Reconnect anything you moved, and make sure the caliper sits true against the disc before you torque anything.
The caliper mounting bolts torque to 195 Nm. That's the value from the manual, and it's a high one for a reason — the caliper is carrying the clamping load of the parking brake, and a loose bolt here is a safety item, not a cosmetic one. Torque to spec, not "snug."
Retracting the pistons drops the fluid level, so top off with the correct spec and check the reservoir after the system is cycled. Then exit service mode through the diagnostic tool, re-applying the EPB and confirming it engages and releases cleanly. A few applications and releases is your verification that the actuator is happy with what you just did — if it's binding or the release isn't full, something in the job needs a second look before you drive off.
Before you put any real load on the brakes, drive gently and apply the brakes a few times at low speed to seat the new pads. Check for leaks, re-check the fluid level, and confirm the EPB warning is off in the cluster. New pads on this car need a proper bed-in before you trust them hard — light to moderate stops, no full stops from speed, and the pads will seat evenly.
There's really one, and it's the one I lead with: never force the piston against an EPB actuator that isn't in service mode. Every other mistake on this job — a slightly loose bolt, a bit of fluid on the disc — is cheap to fix. A damaged actuator is a caliper assembly, and the labor to get to it is not trivial. The service mode step is the whole reason the procedure exists, and it's the one that's free to do right the first time.
Caliper work is the job that pairs with the M840T oil service as the "routine but easy to get wrong" end of the maintenance spectrum, and the RCC II hydraulic flush is the one that intimidates people more. All three are written up with the factory cross-references so you can follow them straight into the service manual for the full procedure text and torque tables.
Found a caliper that wouldn't retract cleanly, or an EPB warning that came back after the job? Tell me — the goal is that the next person reading this gets it right the first time and doesn't buy a new actuator.