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Frankenbrakes and brake improvement discussion

Discussion in 'Downhill & Freeride' started by Udi, Sep 2, 2015.

  1. Rockland

    Rockland Turbo Monkey

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    Comparison of a metal piston from one of those first gen M755's vs. a modern plastic one. Oodles of miles on both, but only one of those levers leaked constantly.

     
    #1121 -   Apr 19, 2019
    Last edited: Apr 19, 2019
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  2. Rockland

    Rockland Turbo Monkey

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    Interesting comparison between the timing ports in the original lever & a more modern servowave lever. They've added to the total timing port area. Likely this is to allow the increased flow rate in the faster moving servowave lever piston. The modern levers seem to still have trouble keeping up.



     
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  3. englertracing

    englertracing Monkey

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    Bother for sience.
    Youd think a quality plastic piston made of delrin with proper length would work nice in an anodized bore.
     
  4. toodles

    toodles Turbo Monkey

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  5. Sandwich

    Sandwich Pig my fish!
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  6. slimshady

    slimshady ¡Mira, una ardilla!

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    The manually adjustable levers were 3D printed for a few pros. I think Bikerumor had the story.
     
  7. Happymtb.fr

    Happymtb.fr Monkey

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    Trickstuff had on their old website something saying that having 4 pads negates the advantages of having quads calipers.
     
  8. HAB

    HAB Chelsea from Seattle

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    I'm with them on that, if you have two pistons per side you can balance pad wear over the width of the pad with slightly larger pistons in front. You've also got more surface area for better heat management and less shit to rattle around.
     
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  9. Mo(n)arch

    Mo(n)arch Turbo Monkey

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    FYI, Magura is offering the „Bruni-lever“ now to the public.
    upload_2019-4-28_21-57-44.jpeg
     
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  10. kidwoo

    kidwoo Celebrating No-Pants Day

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    Oh yeah I forgot. Finally put those chinese anodized pistons in some xts last fall.

    they immediately leaked

    yay!
     
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  11. Da Peach

    Da Peach Outwitted by a rodent

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    Tly it nawr!
     
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  12. kingofsweet

    kingofsweet Chimp

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    hi, first time i post here ^^
    i have a set of shimano saint m820 from 2015 and the rear brakes feel pretty bad.. i bleed it several time but it's still feel mushy and inconcistent lever contact point, excepet when i pump it but after 10 second of release it's again feel mushy.. so i was looking for help at least resolve the problem or maybe change lever or caliper ? the front feel very good nice contact point, pretty stiff and good power but rear..
    i was thinking of cura lever with saint caliper as it's seems to have a pretty early contact point ? any concerns ?

    thanks already for the answer and help ! :)
     
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  13. StiHacka

    StiHacka Compensating for something

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    Check if your rear rotor isn't bent.
     
  14. Sandwich

    Sandwich Pig my fish!
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    time for a bleed and fresh pads?
     
  15. kingofsweet

    kingofsweet Chimp

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    The rotor si not perfect but only slightly bend.

    Maybe again a new bleed..
    Any advice for make a good bleed for evacuate all air bubbles?
    Actually my pad are good, there is plenty of material but yesterday I cover those with oil.. So I need to change anyway but I don't think it's was the problem

    Cheers.
     
  16. kingofsweet

    kingofsweet Chimp

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    Je saigne du frein arrière et avec un étrier en métal, le levier ne semble pas du tout spongieux
     
  17. kingofsweet

    kingofsweet Chimp

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    Fredonner.. I just find the problem the lever is leaking from the gold part at the end of the lever
    Des pièces de rechange ou je suis prêt à en acheter une nouvelle?
     
  18. Olly

    Olly Chimp

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    If the lever is leaking, you'd need to buy a new one. Shimano will sell separate levers and calipers, but none of the parts to go inside them.
     
  19. kingofsweet

    kingofsweet Chimp

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    okay ^^ thanks you. the good things it's that the next time i need spares i can take it from the older lever ahah
     
  20. Olly

    Olly Chimp

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  21. kingofsweet

    kingofsweet Chimp

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    i tried the marshy bleed ^^ but the one you send sounds good too !
     
  22. kingofsweet

    kingofsweet Chimp

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    hi, i come back with my lever leaking from the gold part of the lever.

    after searching on the web it's totaly normal ! it's happen when you overbleed the brake and it's a security from shimano.

    i open it and clean ( it's was really black inside.. ) and you have a rubber over a small hole so when it's overbleed the rubber contract and the excess go to this small hole ,after that i reassembly it and now it's work perfectly !

    another thing i find it's about when you pump the lever it's have a smaller travel, what i find it's seem to be the difference in speed between the piston return and lever return difference.

    because the piston return slower to his initial position than the lever so when you pump it quickly it's create more pressure.

    now the lever feel nice and firm, just the deadstroke of the lever who is a little too big if you have idea ? but it's better now.

    cordially, julien.
     
  23. Udi

    Udi RM Chief Ornithologist: “I Brake for Birds”

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    This is normal, particularly on Saint/Zee brakes because the deadstroke is quite long to begin with (even when new). Over time, the topout mechanisms of the lever piston can wear, causing the starting point of the MC piston in the cylinder to grow further from the timing port (which, once passed, closes the hydraulic system and allows the MC piston to push fluid to the slave pistons). This increases the distance the lever must be moved before the caliper pistons start to move.

    Other types of wear also occur in brakes like the M820, for example wear in the bore itself, and all these wear points combine to increase lever deadstroke, or decrease consistency of the stroke length.

    A good solution is to replace the lever/MC assemblies entirely, even though they may not be leaking. It is up to you if you replace with M820 levers or Cura levers, the overall stopping force may be reduced slightly with the Cura lever however I have not calculated this. The spreadsheet in the first post of this thread may give you some clues.
     
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  24. kingofsweet

    kingofsweet Chimp

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    What a great thing I learn thanks you very much! For the moment I can live with that and as soon as the finance are 9kay I will upgrade to trickstuff dirrettissima lever ^^

    But thanks for the help if it's go worse I know what I have to do.

    The cura interest me because they say on review that the dead stroke was really short so that can be a good option if it's still very short with saint caliper
     
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  25. Inclag

    Inclag Turbo Monkey

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    Came across these while searching for elusive shimano piston seals. Does anyone know if there's any difference between slx, xt, zee, saint pistons? May be willing to give these a try.

    https://m.aliexpress.com/item/32973...ts&spm=a2g0o.cart.99999999.309.6bc53c00WvVvPL
     
  26. KAZHA

    KAZHA Chimp

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    probably this will happen

     
  27. Rockland

    Rockland Turbo Monkey

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    Dimensionally the pistons in all those models are about the same.
    Someone earlier in the thread (can't remember who) mentioned certain low level Shimano servowave levers come with aluminum pistons instead of plastic. Roll the dice and try the China ti ones? I'd be scared.
     
  28. Nick

    Nick My name is Nick

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    update. Cura 4 continue to slay without mods, tweaks or magic spells.






    ( probably just jinxed myself)
     
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  29. StiHacka

    StiHacka Compensating for something

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    My Saintguras refuse to die. Pistons are 100%, Saint levers show some sign of use but still go strong. Just flushed the old oil and while it contained products of alloy oxidation, it wasn't really too bad.
     
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  30. marshalolson

    marshalolson Turbo Monkey

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    Curious: How much use?
    About to make some m988/mt5 shiguras this weekend
     
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  31. jstuhlman

    jstuhlman We noticed.

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    finally got the 203 rotor to work without rubbing with my 4 up front...it took the addition of one shim/washer under one end of the adapter. will give it proper shakedown in the hills tomorrow.
     
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  32. StiHacka

    StiHacka Compensating for something

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    Since October 2015, maybe ~4000 miles? Maybe a little more?
     
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  33. marshalolson

    marshalolson Turbo Monkey

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    Awesome! Thanks... stoked to get them running :)
     
  34. Kurt_80

    Kurt_80 Monkey

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    Waiting for feedback....:popcorn:
     
  35. maxyedor

    maxyedor <b>TOOL PRO</b>

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    How's the power on those? Comparable to Saint & MT5/7? Thinking about scooping up a pair.
     
  36. Nick

    Nick My name is Nick

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    behind you, don't wait up.
    I replaced M820s with these Cura 4s. Tons of power, great feel at the lever. A bit more effort to bleed, but I'm sold on them.

    No experience with modern Maguras.
     
  37. jstuhlman

    jstuhlman We noticed.

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    interesting...cura 4 with 203 vs 180 seemed to heat/pump up more on sustained descents. will have to continue monitoring. if i can get up to snowshoe next weekend that would be a good follow up. descents i did today were rough and steep. just for reference, one was about 1500’ over 3 miles; another was about 800’ over 2 miles, and the last was about 1500’ over 3 miles.
     
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  38. Nick

    Nick My name is Nick

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    behind you, don't wait up.
    maybe braking too much?
     
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  39. englertracing

    englertracing Monkey

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    I also have the cura 4,
    I think you need a bigger syringe than the formula kit to bleed the rear.

    Other than that they seem good. Basically feel like a shimano without the servowave
     
  40. Da Peach

    Da Peach Outwitted by a rodent

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    My MT7 are still running strong.

    I just bled the rear the other day to firm it up after a pad change. The process was fairly painless and worked really well.

    The key seems to be to not rush, be sure there are no tiny bubbles hanging in the fluid in the syringe at the lever.

    I used this method: