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The pistons in my very early Hope Minis are sticking, meaning that instead of creeping slowly through the seals and self-adjusting for pad wear over a long period of use, the pistons stay back causing increasing amounts of lever travel then suddenly jump though and stick on when you grab a big handful of brake. When this happened on C2C recently I had to force the pistons apart to free the wheel and the only way to do it was to bleed out some fluid at the caliper.
Can anybody explain this odd behaviour?
piston/bore corrosion from grime
use of wrong lubricants on pistons and levers
lever master cylinder dying
water in fluid corroding from inside.
old fluid
the seals are orings effectively and orings degrade over time due to exposure to fluids and UV
the old silver calipers used to oxidize badly - most things when they oxidize expand
Certain seals swell very quickly with the wrong type of fluid, but I assume this isn't your issue 😀
Cheers, Rich
Even with the right fluid they swell over time, they're resistant to DOT fluid, but not impervious to it. So they're either dirty, corroded, swollen or all three.
DOT brake fluid will swell and degrade the seals, and inside face of your brake hoses over time. Collapsed brake lines can also prevent fluid from returning freely, also making the piston not return.
You should replace DOT brake fluid every year to slow down its effect on the seals and brake lines.
Ive got some XT 4 pots from about 1999 that have never had a bleed since first setup. Still using them on my SS. Worried now about them failing at the wrong time.
Thanks, sounds like I need to give the brakes a full refurb as they must be 15 years old. I wonder if Hope will do this for me?
This how my minis/M4s died.
Mineral oil is a bit kinder to the seals, they're probably fine. You'd be unlucky to have both go simoultaneously anyway.Ive got some XT 4 pots from about 1999 that have never had a bleed since first setup. Still using them on my SS. Worried now about them failing at the wrong time.
Usuaaly in that case they feel fine while braking as the fluid re-expands the hose, but never they retract as the hose becomes a one way valve so the pads rub.Collapsed brake lines can also prevent fluid from returning freely
The pistons in my very early Hope Minis are sticking
Do you have the original two piece silver calipers?
Do you want a set of spare pads? I have some lying around from years ago - unopened. Don't want to throw them out 🙂
Yes, thanks! PM sent.
Seals will, breakdown, swell, degrade over time so yes really they will.
I've got some original seal service kits for the silver mini I think. And a still working spare brake I think. Yours if you want them.
Wow! Some great generosity on this forum! Another PM sent.
Hope can refurb them for £45 each and then another £26 each to replace the pipes but I can do all that myself if I can get the bits.
Thanks again Molgrips and Fat-boy-fat.