i see, the only info i pulled up on international standard related to 6 bolt disc mount and yes i am post mounted.

calipers are br-m 525 on 160mm (ish) rotors.

rear was spongy before and since i worked with the bike inverted, school boy style (though i did refrain from putting a clothes peg and piece of card in the spokes) the lever now hits the bars so will defo need bleeding.

thanks for offer of gubbins mboy, i might take you up on that as as yet i have no bike specific kit.

have knowledge of cars and motorcycles with single, twin and four piston calipers and both fixed and floating calipers or discs.

cleaned these shimanos up earlier, quite surprised that they were twin pistons. initially they were squeal free, then i cleaned the disc and they squealed again! only had wd40, solvent cleaner and some crap three-in-one copper grease (it's a spray grease and goes everywhere… not ideal)

gonna get some new pads, brake fluid, cleaning materials and proper grease tomorrow to do the job properly.

as for IS and post mount, IS is "international standard" and applies to disc mount but what is "post mount"

they're hydraulic shimanos, original fitment. as for IS or Post? ain't got a clue, said i was a newbie! thing is a couple of mates were in front of me, they were on their brakes too (much newer & larger discs!) but weren't clearing the woods of wildlife. think i'll go to the garage, wash the mud off and have a play.