I have pistons that will not retract fully after a particularly muddy weekend of bikepacking. I have tried the usual lubing the pistons with dot 5 and working them in and out. This only seemed to make things worse! The caliper was rebuilt recently with new pistons and seals and has not seen a huge amount of use since so I’d not expect to have to rebuild it again. The other 3 M4 brakes I rebuilt at the same time seem to be fine and the old hopes I had never got rebuilt.

What am I doing wrong? Any suggestions?

Whats the piston lube of choice? Red Rubber Grease or Plain old Dot 5? Anyone tried the Hope/Hunter’s Silicone Lube? Any better?

They won’t retract fully if the pads have worn; more piston will show the less pad material there is.

If you know that already and the pistons are sticky though. Take the pads out, squeeze the lever a couple of times go get more piston showing (be careful not to pop them out). Then use silicone lubricant to lubricate the pistons/seals. Sex lube works well and is easily acquired! The Durex stuff that comes in little bottles.

Hope recommend silicone (non oil based lubricant) for the job and supply it in their dealer kits.

You can buy the actual Silicone lube that hope use from plumbers stores, I bought a big tube of it when I last serviced my m4, can’t remember name but it’s green and cost about £7, better than using dot.

http://www.bikegoo.co.uk/components-c8/disc-brake-spares-c11/hope-silicone-lubricant-p519/s1194?utm_source=google&utm_medium=cpc&utm_term=hope-silicone-lubricant-httlube&utm_campaign=product%2Blisting%2Bads&gclid=CjwKCAjw3_HOBRBaEiwAvLBbou6jMv7VX8iqwnkYHunOPpdrQB1Cihh5rNmcFTkokaYShheWgMF6MhoCQBgQAvD_BwE

This stuff is what I use on my Tech M4’s, all of the pistons were sticky, I popped them out as far as I dare then cleaned them with Isopropyl alcohol and then lubed with the Hunters silicon, works well.

Sex lube works well and is easily acquired! The Durex stuff that comes in little bottles.

brings a whole new meaning to pump the brakes.

My solution with previous Hope
Issues is put them in a padded envelope. Send them to the helpful hope man and get them serviced. Both times it’s only cost 80 quid and been turned around in a couple of days.

Maybe not the answer you were looking for but it saves a lot of hassle.

I hope you mean DOT 5.1 rather than 5, if not there’s your problem.