Leave the old pads in. Then spread them apart by putting a flat head screw driver in there and turning it sideways, any strong/flat piece of metal would work though. Once the pads have been pushed back all the way, take them out and put in the new ones.freeriderB said:
Don't do this with the new pads, as it will ruin the surface. It's really the only way to get all 4 pistons in at the same time.