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Spent an hour or two last night trying to sort out a rear Hayes nine brake to no avail. Bled it twice - the problem seems to be really bad sticky pistons. Range of movement is way too small when the lever is pressed. Brake fluid on them no good, actually took one out of the caliper to have a look and clean it but that didn't do the trick either.
Reading online it seems to be a big problem with this brake - a litany of woe regarding sticky pistons. Anyone encountered this problem and can suggest anything? Thanks.
A pair of juicy threes?
(seriously!)
Or if you must try make the hayes work, I assume they've over a year or so old? In which case, probably need new seals. New pistons too while you're at it will be worthwhile.
It will cost you more to fix if you need parts than buying a new one off Chain Reaction for 30 odd quid
Try removing both pistons and seals, cleaning them(and the grooves the seals sit in,also check for corrosion build up in there-if there's a noticable ammount i'd bin it) and re-assemble with a smear of silicone grease on everything.
Thanks for the tips - the brake is several years old. I rate them highly though, so I'd like to keep it. The front works fine - great power and a grabby sort of style that is different from other brakes I've used.
Just seen the hundreds of spare Hayes parts on CRC so I guess that's a good place to start.
After having waged war on a pair of Nines a couple of months ago, and failing miserably to get them operating to any decent level, I'd recommend buying new calipers or complete brakes from CRC. Think the Hayes service kits+bleed kits are poor value when a pre-bled brake was on offer at £40+.
One problem I noticed was corrosion inside the caliper body which meant there were tiny weeps around the seals and prevented the brake from being bled. Couldn't find any easy way to clean the seal grooves without causing damage.
Good luck
Iain
bleeding them won't help if the pistons are sticky ( as you've found ). maybe a grandmother/egg situation but have you tried holding one pad back, and letting the other come out when pressing the lever, release pressure then push him back home, repeating a few times, then going to the other side and going again?
if they're just a bit 'reluctant' this could help?
Best bet is to do one of two things.
1) strip the claiper and give a full clean and replace all the internals or
2) pump the pistons so they are nearly out both sides, coat in GT85 or any other light oil and then clean outer piston with a cotton bud. Push the pistons back in and then pump out again and give another spray of oil. Now you should find they are free and should now last another 40 rides before filling with crap again!
Magnesium brake callipers... Genius! Guess they never salt the roads where Mr Hayes comes from..
To fix them without getting new pistons you need to take the piston and seal out and very gently sand (or better, wet and dry) the outer ring of the cylinder- the part nearest the pad. Don't sand the wet part (the bit with fluid in, behind the seal). Clean the piston and cylinder thoroughly and replace the seal the opposite way round to before. If it was very corroded then the piston will have a groove all the way around it. If that's the case, it's ****ed and you need to go buy some real brakes.
Had a set on my Saracen Zen, swopped them out for Shimano and have not had to change them since. As mentioned before pistons were seazed so would needed replacment. Not the most eviromentally friendly brake fliud either.