Saturday night and I am doing a DIY serive on the Hope minis, and am a bit stuck.

One of the pistons will not retract sufficiently – well at all. I tried pushing is back to no avail.
the other piston has gone back all the way. I need to put new pads in so need both pistons all the way back in?

Any useful help,many thanks?

I did say useful!!!

Have you tried WD40?

Just done my M4's and the pistons go back easily as long as they are pushed back squarely.

You could always pump the pistons out again – make sure that you have something centered & fixed (the M4s have a grove down the middle that a piece of 2/3 mm steel strip can sit in) between them so they don't over extend – just in case the problem one is out of line.

WD40 them – clean with an earbud – spray again – let the WD40 dry a little – and then try pushing back again.

Good Luck

Step away from the WD-40, it is devils spunk.

As MLC says but use brake fluid in a syringe to lubricate the seals.

Some oils will cause the seals to swell – only use brake fluid or rubber grease to lube seals.

Work the offending piston in and out – give it a clean as well.

I work my M4 pistons in and out and lube them with some silicone

seems to do the job

If it won't go back in at all (as opposed to being a bit sticky), then you may need a new piston. One of my Mono Mini pistons wouldn't go back more than half way – turned out there was a bit of debris stuck behind it (which I think chipped off the side of the piston). A new piston is only a few quid, plus another couple of quid for the seals, and relatively easy to pop in if you're comfortable with dismantling stuff, bleeding, etc.