sorry but wrong as far as IS mount callipers
post mount callipers are the same but IS mount are not - the legs on the rear are longer than the front.
by default, front IS forks run with 160 mm disc and so does the rear. If the rear caliper is fitted at the ront, then a 180 mm disc has to be used. Likewise if front is fitted on the rear (frame), then 140 mm disc has to be used.
There are adapters for IS callipers that let you run larger disc.
..... tried ages searching on the net to find F+R IS calliper,in the end too a photo of mine.