Results 1 to 5 of 5
  1. #1
    mtbr member
    Reputation:
    Join Date
    Dec 2008
    Posts
    26

    Hope Mono Mini Problem - lever and cease

    I have a Old Mono Mini Brake 160mm Rotor.

    If I take my wheel of and pull the brake I can see that only one of the pistons is moving. Once I have squeezed it, it is then very hard to separate them, so that where is enough gap to fit my wheel back on.

    What should I do to uncease them?

    Another problem I have is that the small metal bar which is attached to the brake lever, which has a ball shape on the end, has wore out the inner part and therefore is loose. So sometimes my lever comes out [which is dangerous obviously]

    I have found this online but am unsure if it would work.
    http://cgi.ebay.co.uk/HOPE-MONO-MINI-M4-DISC-BRAKE-LEVER-SPARE-PARTS-KIT_W0QQitemZ370112036898QQcmdZViewItemQQptZUK_spo rtsleisure_cycling_bikeparts_SR?hash=item370112036 898&_trksid=p3286.c0.m14&_trkparms=72%3A1301|66%3A2|65%3A12|39%3A1|240%3A13 18#ebayphotohosting



    One final question, If I have a 160mm currently but want to get a 203mm, can I just replace the rotors, or would I have to get a new brake?

    Thanks

  2. #2
    ...idios...
    Reputation: SteveUK's Avatar
    Join Date
    Apr 2006
    Posts
    5,662
    It sounds as though you have a failed seal on the caliper and that it's also time for a lever overhaul. Here's a guide for a caliper seal change and here's a guide to overhauling the lever. I'd recommend Chain Reaction for the caliper seal kit and lever rebuild kit as they're almost always cheaper than anywhere else. You'll need to pick up some DOT fluid (4 or 5.1) as the system will obviously require refilling and bleeding afterwards.

    As far as moving up in size with the rotors, you can get a +40mm adaptor (also at CRC) which would then allow you to run 200mm rotor.
    .
    .


    What luck for rulers, that men do not think - Adolf Hitler

  3. #3
    mtbr member
    Reputation:
    Join Date
    Dec 2008
    Posts
    26
    Thanks Steve, could not have hoped for a more informative reply!

  4. #4
    mtbr member
    Reputation:
    Join Date
    Nov 2007
    Posts
    1,255
    Caliper problem #1 (only one piston moves) is just a sticky piston. All the brake dust clogs up the piston bore and the piston then doesn't move freely. When you squeeze the lever, the piston that is easier to move will give way under the fluid pressure and the other one will stay still. If you hold back the piston that is moving (with a screwdriver or other tool), the sticky piston will start moving. Spray the whole assembly with either of GT85, isopropyl alcohol or methylated spirit and get both those pistons moving and clean.

    Caliper problem #2 (can't push piston back) happens because you can't always push the piston back evenly and it becomes misaligned in the bore and gets stuck.

    If the brakes haven't been bled for a long time, the DOT fluid will have absorbed moisture past the seals and will have increased in volume. This will prevent the pistons from being pushed all the way back. Don't know if you have this problem also, but watch out for it.

  5. #5
    ...idios...
    Reputation: SteveUK's Avatar
    Join Date
    Apr 2006
    Posts
    5,662
    "Spray the whole assembly with either of GT85, isopropyl alcohol or methylated spirit and get both those pistons moving and clean."

    The GT85 I would be doubtful of - too much oily residue - but do NOT use Isopropyl Alcohol or methylated spirits to clean around pistons seals. Both products will eventually dry the seals, stiffening them and so rendering them useless.

    There's a silicone spray which you can pick up at Maplins or B&Q. This is the ideal solution for cleaning calipers as not only will it help to keep seals soft and maleable enough to be able to do the job, but, after all excess has been wiped away, it will dry without wet residue and leave a semi-protective coating which, in my experience, also appears to help keep the caliper clean afterwards.

    Seal cleaning should only be done with either DOT fluid or an appropriate silicone-based lubricant.

    A screwdriver, used carelessly, can crack or chip a phenolic piston. Use a plastic tyre lever for holding them or pushing them back into the caliper.
    .
    .


    What luck for rulers, that men do not think - Adolf Hitler

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •