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  1. #1
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    Shimano BR-M755 (XT - 4 Pistons 4 Pots)

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    Hoping I could get some information from the large experience/thought pool of mtbr

    1) What's the evolution of the 4 piston brake design? I seem to recall they were originally adapted from Grimeca's, but not too sure. What I find odd is that until the 4 piston Saint came out, all other Shimano dbs have been 2 piston.

    2) Why have they become so popular recently?

    3) For users, how is their performance? any problems with parts?

    4) How do they compare with current newer dbs?

    5) From a design standpoint, how are they different from the m810 saints?

    Thanks everyone!

  2. #2
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    As I know it, they were derived from the Grimeca Disc brake that eventually became known as the System 8 but use mineral oil instead. It seems all parts are the same except for seals. I haven't tried them myself but it seems they still have a lot of loyal followers if that says anything.

  3. #3
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    4 pistons have more clamping power. The surface area of the pistons in a 4 piston caliper is greater than in a 2 piston caliper. The XT brake also has 2 different sized pistons to try and equalize the pad wear. Go to Wiki and look up hydralics. But, more parts means more sources of problems. Seals, sticking, etc. This is why most cars have 1 piston calipers. Or as a great military leader once said, "tmmp". Too many moving parts.

  4. #4
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    I understand that they were designed by Grimeca and Shimano later licensed the design and manufactured their mineral oil version when it realised that it had fallen behind in the disc brake stakes. SRAM also produced a copy (9.0?) and I think another version was called XLS. Reports in the early-mid 00s indicated that the Shimano quality was better, with Grimeca parts breaking more often. But I am sure that there are quite a few people still running both.

    Tim

  5. #5
    nnn
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    I got my hands on a NOS calliper which hadn't even had its stickers taken off. Bought some LX levers and a 90-straight hose kit and some EBC downhill pads (same as Hope M4) and I couldn't be happier. They certainly look unique to all brakes out there! Not to mention absolute power with amazing control.

    The new saints are one piece and I think have slightly larger pistons and a larger internal oil volume + better seals. I'd love to have a go, but don't have the dough
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  6. #6
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    great information, thanks everyone - keep it coming!

    btw, what years did they sell this brake?

  7. #7
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    [QUOTE=nnn
    The new saints are one piece and I think have slightly larger pistons and a larger internal oil volume + better seals. I'd love to have a go, but don't have the dough [/QUOTE]

    The new Saints are 2 piece. They are a redesing of the 755 for use with the new selvo brake levels, 755 are not design for selvo brake level and the seals will be damage because of the extra preassure brake line pressure put out by them. They are also post mount which the 755 never came in.

    I got 4-pot XT calipers and they are great. I use mine with 180/160 rotors, XTR brake levels, sistere pads and Goodridge line. The modulation and power is great specially in the front. They feel way better than the XTR calipers they replaces. If you can find a set I highly recomend them, if not the Saints are good artenative. Oh one more thing they look cool
    If I disagree with you, it's because you are wrong.

  8. #8
    dirt visionary
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    I have both the grimeca and m755's Love em wouldn't give them up for anything (except maybe the new saints)I have tried most other offerings out there and like the 4 pot design best.
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  9. #9
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    thanks! sounds like a solid choice then! i'm looking to get a pair, just worried about finding replacement seals and/or diaphragms - anyone have a good source?

  10. #10
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    no one has an idea on diaphragms? can't seem to find any online...

  11. #11
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    Reservoir kits for M755 levers are available here:
    http://www.ride-this.com/index.php/s...755-right.html

    If you wants seals for the calipers I don't think Shimano made them. You may be able to find them at a bearing/seal supplier.

    Tim

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