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Thread: Sticking brake piston

  1. #16
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    6th June 2011 - 14:55
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    Sorry, a typo. Meant to be scribber. Its probably a bit heavier than a dentists tool but was used gentlly and didn't scratch the hell out of the casting. Their was a little bit of crap there, not a huge amount. Guess I will have to pull the other caliper apart to get a good comparison.

  2. #17
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    13th June 2010 - 17:47
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    Quote Originally Posted by Premature Accelerato View Post
    Cleaned it with the curved end of my trusty old scrubber. I have just pulled it apart again and put the piston in the pot without any seals. It slides in and our easily. I then put the oil seal in by itself and the piston works the same as the others. I then put the dust seal in and the bloody things tightens up to buggery. So I would guess that perhaps the seal is slightly too big or the seal is a little over size. All the extra cleaning at least gets me a 1 1\2 turn of the wheel when I give it a spin. Enough ya reckon?
    Surely you mean the dust seal is Undersize. Are you putting any rubbergrease on the OD of the piston or the ID of the seals ?
    Turning the dust seal inside out can often reveal accumulated crud.
    Bit like inspecting the ID of Methamfeatherston I suspect....
    Reason is a tool - remember where you left it..... The late, great, John Clarke

  3. #18
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    6th June 2011 - 14:55
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    By over size I mean it is too tight but I guess you could call it undersized. I have put a small smear of grease I got from Boyles a couple of years ago, to lubricate things. I have used the same grease many times on brake seals and it has never given me any problems. It is red in colour but I cant remember its brand/trade name. I'll get there in the end.

  4. #19
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    28th May 2006 - 19:35
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    Quote Originally Posted by Grumph View Post
    Surely you mean the dust seal is Undersize. Are you putting any rubbergrease on the OD of the piston or the ID of the seals ?
    Turning the dust seal inside out can often reveal accumulated crud.
    Bit like inspecting the ID of Methamfeatherston I suspect....
    i snuck up the hill a wee while ago and altered their sign.....
    take a good look at the little square boxes too.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  5. #20
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    28th May 2006 - 19:35
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    so did you just replace one seal?
    did you clean the grooves out thouroughly, ie with a solid scraper to pick the shit out of it,
    if you move the seal to another hole them if the issue follows it there it's the seal,

  6. #21
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    20th January 2008 - 17:29
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    Its unlikely but if the compensation port ( very small hole)in the master cylinder is partially covered by the piston seal pressure builds up and pads drag. can be caused by sticking brake lever/actuation mechanism.
    DeMyer's Laws - an argument that consists primarily of rambling quotes isn't worth bothering with.

  7. #22
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    6th June 2011 - 14:55
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    I have now cleaned the absolute shit out of these calipers. I measured the dust seals and the offending seal was actually 0.2mm thicker than the nearest sized seal. I have put that seal in a different pot with the smallest dia piston (albiet by only 0.02mm). Although the amounts are not much, surprisingly the wheel now spins quite freely.

  8. #23
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    28th May 2006 - 19:35
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    Quote Originally Posted by Premature Accelerato View Post
    I have now cleaned the absolute shit out of these calipers. I measured the dust seals and the offending seal was actually 0.2mm thicker than the nearest sized seal. I have put that seal in a different pot with the smallest dia piston (albiet by only 0.02mm). Although the amounts are not much, surprisingly the wheel now spins quite freely.
    yah that's 5 thou, for the seal, usually it's lumps in the grooves that can't be easily seen that cause the issue., well done

  9. #24
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    27th November 2012 - 11:25
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    time to upgrade to nissin calipers --- glad to hear its sorta-sorted ...

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