Worst case, you can take a screwdriver or thin pry bar and pry the pads out from the bottom of the caliper. You can use the rotor hat or studs (if you have them) as leverage on the front side. There's something to pry against in the back.
ST60s seem to be a minor PIA to get the pads in and out. The pads come out with a little effort in the ST40s. The key is to fully depress the pistons with spreader. I do apply some anti seize to the sides of the pads to make removal a little easier.
The pads should be snug as to avoid pad rattle...a really annoying clack, clack, clack sound at low speed. If they are too loose they'll rattle.
2013 F30 328i Melbourne Red
2011 E90 M3 Monte Carlo Blue
2004 E46 M3 Imola Red