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  1. #1
    billyboy197
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    Hope Mono Mini Binding - Help Please

    I've got a set of mono minis that I've had a couple of years that have behaved faultlessly up until last week. The rear is suddenly binding on the rotor and the caliper makes a creaking noise when I pull the lever to apply pressure. The lever feels very spongy. I have remove the pads and thoroughly cleaned the caliper, extended the pistons and lubed them but no difference. The pistons don't spring back into the caliper when I realese the lever like the front ones do. I have not changed the oil before as I have not felt the need to.

    Are these classic sypmtoms indicating a need to change the oil or does it sound more like new seals required? I'm sure it's nothing too sinister but I could do with some advice.

    Thanks.

  2. #2
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    Reputation: SteveUK's Avatar
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    Both pistons? I'd try a bleed before I started pulling seals. It's possible that the DOT has turned 'jelly', as it can do if left in the system for too long. It'll typically thicken up behind the pistons and in the master cyclinder, so it may be worth your while just removing the MC cap and checking the condition of the fluid sitting in there.
    Check this link for the procedure to replace lever/caliper seals. Follow the 'lever' link for bleeding instructions.
    Last edited by SteveUK; 01-27-2008 at 08:46 AM. Reason: insert link
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  3. #3
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    Quote Originally Posted by SteveUK
    Both pistons? I'd try a bleed before I started pulling seals. It's possible that the DOT has turned 'jelly', as it can do if left in the system for too long. It'll typically thicken up behind the pistons and in the master cyclinder, so it may be worth your while just removing the MC cap and checking the condition of the fluid sitting in there.
    Check this link for the procedure to replace lever/caliper seals. Follow the 'lever' link for bleeding instructions.
    I agree, I had this happen on a set of old mono's. Completely drain then flush good with dot 5.1

  4. #4
    billyboy197
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    Thanks, I'll start with a bleed then. If the oil has turned badly to jelly will a flush and bleed clear it all out or will I need to strip the caliper down still?

  5. #5
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    "If the oil has turned badly to jelly will a flush and bleed clear it all out or will I need to strip the caliper down still?"

    This is the question. It's the kind of thing that I'd judge when I opened the MC. If the MC cap hasn't been off for a year or so, you'll probably need to replace the diaphragm that sits under it, so you may as well pick up a full seal kit and bore cap tool while you're ordering. Even if your bleed gets the brake up and running, and given the fact that the brake has seen no maintenance or fresh fluid (DOT also lubricates the seals/pistons) for at least two years, I wouldn't be surprised if one or both caliper seals agev up on you in the not too distant future. If the bleed doesn't flush the system (you'll probably need 8-10 MC's worth if it's really gummed up; just watch at the nipple for the DOT to come out free of discoloration), then you should replace at least the caliper seals. A lever seal overhaul on top will leave your Mono Mini feeling 'as-new' and is really worth the extra half hour of work.
    All of your seals kits and tools will set you back less than twenty quid, plus a couple of hours to do the job.
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  6. #6
    billyboy197
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    Just bought some 5.1 from motorbike shop. Didn't know how much I needed so bought the 250ml and the 1ltr bottle. How much am I going to need per flush? I'll take the one I don't need back.

  7. #7
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    250ml will do you fine.

  8. #8
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    Update? I was curious to what the problem was since I'm considering these for a new bike.

  9. #9
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    Quote Originally Posted by billyboy197
    Just bought some 5.1 from motorbike shop. Didn't know how much I needed so bought the 250ml and the 1ltr bottle. How much am I going to need per flush? I'll take the one I don't need back.
    If you get any on your frame or fork quickly wash it down with rubbing alcohol it will eat you paint/finish. I usually keep some handy in a squirt bottle.

    Just flush the whole 250ml through to make sure you get all the goo out. Once you've done this then somewhere safe, like grassy area make sure the brakes function properly under stress. If they don't time to take the calipers apart and replace seals.

    Keep the 1 liter until you know the job is complete.

  10. #10
    billyboy197
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    Man that was easy!!!! Rear seems fine now. I used about 100ml, the old fluid didn't look too bad as it came out although there were a few bubbles. Just one question though:
    The pistons were stuck bad before I started and wouldn't go all the way back in (say 2mm sticking out each side). I wedged them while bleeding as instructed and now I'm finished they move freely and will go all the way in. Is this going to cause a problem in use as I suppose there is now slightly more fluid in the system than there should be. Lever operates fine, pads clear the rotor, everything looks good. Just curious
    Thanks for the tips.


    For those who want to know if these brakes are any good, I'd say Yes, they have performed faultlessly for 4 years (I just found the receipt ) and this is the first time I have bled them . I ride XC-AM and they are just fine.

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