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saint brake, m820, inconsistant.

santabruzsantabruz Posts: 40
edited February 2013 in MTB workshop & tech
sorry if this has been asked before,,,
i was just wondering if anyone on here is having or has had any problems with the new m820 saint brakes.
most of the journo's at the product launch in whistler last year, reported inconsistant feel, there are lots of threads on various forums about it, yet shimano claim to know nothing about it,
so has anyone else experianced this inconsistant feel in their brake.

on the ones i have the bite point will change randomly, one minute it bites close to the bar, next time i pull the lever it will bite at the top of the lever pull. then it will go back to the bar, then bite near the middle of the lever pull. it's weird. and very un nerving, lots of people on mtbr have reported this problem, and they have tried bleeding their brakes multiple times. but it doesnt seem to make much differance.

Posts

  • Does it change the longer they're used?
    And if you pump the lever, does the feel return?

    My only issue with Shimano brakes is the mineral oil.. it "fades" pretty quick over persistant use, my deores have a similar issue and pretty much died on the last few descents at Afan!
    However, if you pump the lever, they do start to come back.

    Same thing happened with my Saint M810's.
  • peter413peter413 Posts: 5,120
    Can't say I've had this problem with either the M810 or M820 Saint's except when they needed a good bleed. The bite point can occasionally change slightly but this is just one slight bubble causing this I've found, easy to fix with a very quick bleed but I don't usually bother. I haven't noticed this on either pairs of my Deore's either except of course when they needed a bleed.

    From what I've read about journalist's having this problem, it's only when the brakes are dragged for a long time. Shimano do know about the problem, they just don't know how to fix it I think. I'm going to assume that it's just the fluid being put under more pressure and any air that was in the fluid is being turned into a little air bubble causing the problem kind of like degassing the DOT fluid for Avid and Formula bleeds in which case I can't see there being a fix for it. The old M810 levers were known for occasionally sucking in a slight bit of air unexpectedly.

    I've been very very happy with my M820's though and they are worth persevering with IMO, bags of power and modulation in what I've experienced to be a very reliable package.
  • The RookieThe Rookie Posts: 27,804
    Mineral oil has a lower boiling point than DOT......
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • Mineral oil has a lower boiling point than DOT......

    I knew there must be a reason for using brake fluid in brakes... :wink:
  • peter413peter413 Posts: 5,120
    It's a badly designed brake really if you're managing to boil the fluid on a push bike, at least riding normally anyway. Plus surely your pads would be totally ruined if you were managing to boil the fluid. Mineral oil has never once caused me an issue and I've got my brakes pretty hot at times.
  • bennett_346bennett_346 Posts: 5,029
    I thought this new line of shimano brakes was meant to be "like, amazing dude" and stuff...
  • I thought this new line of shimano brakes was meant to be "like, amazing dude" and stuff...

    While I think they're great and very well modulated, they really need to ditch the mineral oil. Its too easy to boil on a long descent and once its boiled, they're censored until bled!

    Could have saved a lot of effort on the ice tech stuff by changing the oil lol!
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