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Brakes rub after used.

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  • The RookieThe Rookie Posts: 27,748
    OK, you tell me what seperates the brake fluid from air in a car that is akin to the diaphragm on an MTB system such as Avid, Shimano or Tektro.

    Also explain how an ABS system with valves open (normal condition) is different to a non ABS car in respect of said diaphragm, bearing in mind the ABS car (assuming dual build) will usually have the same resevoir,M/C, servo (brake booster) etc

    Nothing you say suggests you know anything about car brakes.....or MTB brakes.....
  • levolonlevolon Posts: 78
    edited June 2013
    stubs wrote:
    Jesus wept do any of you guys know what your spouting about. Just because there is no vent hole it doesnt mean its a closed system. You all claim to be engineers with more knowledge and experience than God and probably work on repairing X wing fighters for all I know but you dont know the difference between a closed and open hydraulic system.

    I give up and bow to your 50 years experience of working on everything.


    yes id give up same as i have ,,,

    not a fooking clue between them have they :roll:

    Mtb brakes are a mystical thing created by the Andromeda beings and nothing like All bike car hydraulic systems that use dot 3-4 and 5.1....

    cant wait to see their reasoning on dot 5 !!!!! that will be funny

    leave em too it bud , but in a week or 2 they will be spouting about the need for regular fluid changes , you wait and see :wink:

    oh and FYI a motorcycle MC has a pin hole in the cap to allow air in as the diaphragm collapses , the diaphragm is air tight too . so in fact fluid WONT pour out when upside down...
    so a closed system like your mtb brake lol
    keep at it guys
  • The RookieThe Rookie Posts: 27,748
    I notice you 2 never come out with any actual detail to rebutt what I am saying....try doing it eh.....
  • levolonlevolon Posts: 78
    I notice you 2 never come out with any actual detail to rebutt what I am saying....try doing it eh.....

    we dont need too its all on the net go fooking read as you take no notice of anyone
  • The RookieThe Rookie Posts: 27,748
    Most the links provided have been just plain wrong as I've corrected for you...so intead of saying its all on the net, YOU tell ME what bits precisely I got wrong please, as I had the courtesy to do for you rather than just resorting to name calling.

    The bikes I checked have no diaphragm, I dare say some may, cars definately don't by the way.
  • stubsstubs Posts: 5,001
    If as you regulary claim to be you are a multi talented engineering genius who has had simultaneous careers as a Hydraulics engineer, motor engineer, mechanical engineer, civil engineer, aviation engineer and no doubt next week you will claim to have built the Channel Tunnel whilst at the same time invented the paperclip go onto Google and put ABS system in the search box. Or did you invent ABS as well as the paperclip.

    Go on go on go on go on go on go on we know you dont want to but go on go on go on go on. If your not to busy rebuilding the nation one career at a time that is. :lol:
    Fig rolls: proof that god loves cyclists and that she wants us to do another lap
  • levolonlevolon Posts: 78
    stubs wrote:
    If as you regulary claim to be you are a multi talented engineering genius who has had simultaneous careers as a Hydraulics engineer, motor engineer, mechanical engineer, civil engineer, aviation engineer and no doubt next week you will claim to have built the Channel Tunnel whilst at the same time invented the paperclip go onto Google and put ABS system in the search box. Or did you invent ABS as well as the paperclip.

    Go on go on go on go on go on go on we know you dont want to but go on go on go on go on. If your not to busy rebuilding the nation one career at a time that is. :lol:


    think we're witnessing the birth of BEGINNERPEDIA here !! so all we will need in future :lol:
    I think the claim that all the links are Wrong is quite possibly the most profound thing ive seen on a bike forum lol i nearly passed a kidney laughing ...

    ive never heard a Engineer use the term Moderately when answering a Q about how tight should i do it up either??
    Any engineer worth his salt would at worst give a rough torque value as Moderately is so vague its ridiculous .
    although ill give that a try on my ham fisted mate when he wants a torque value for a laugh...

    i see why you have 11.000 post now and i think you need to concentrate on you work instead of pissing about on here all day sweetie ..
  • The RookieThe Rookie Posts: 27,748
    Still no answers then Ion - full of hot air then - no point trying to educate someone who is voluntarily deaf.
  • levolonlevolon Posts: 78
    cyd190468 wrote:
    Here's a question. If mtb brakes are just like motorcycle brakes then why is it that if you undo the bleed valve at the calliper and pump the lever the fluid doesn't come out? One suirt comes out but then the seal at the lever causes negative pressure so air gets sucked up the brake line rather than the fluid coming out. It just goes back and forth. The seals in mtb levers are very different to the concertina type you see in car and motorcycle brakes. That's why when you bleed mtb brakes you generally have to open a valve at both ends. Also how many automotive brake systems are there where you fill the system totally with fluid. There's no full mark, you expell all air from the system and then do up the bleed valves at each end. And regarding dot fluid about half of the current mtb brakes use mineral oil as the hydraulic fluid, not that it really makes any difference just surprised you didn't seem to know.
    BR6848.jpg
    There's not enough give to fully compensate for pad wear so you end up adjusting lever reach so you don't squash your fingers.
    The newer avids hardly have any reservoir at all
    avid_elixir_cr.jpg



    heres your answer

    same thing happens on a motorcycle brake if you open the bleed and pump the lever as the fluid just pulls back as the mc piston returnes..

    so you are again misguided .
    if you are bleeding without a pipe or air lock device this will happen on mtb or mc brakes

    go try this , go to bike and undo bleed half a turn and then pull lever to the bar AND hold it there ..
    nip up bleed nipple and then release the lever ... oh what do you know it is solid still!!!
    basic stuff this guys but if people read your advise on bleeding etc its no wonder they get it wrong...

    and when did we finally get the brake fluid thing then guys ?

    happy

    ive bled more brakes than i care to remember
  • supersonicsupersonic Posts: 82,708 Lives Here
    Having read through I am still not sure what the disagreement is about lol. Is it just slightly different definitions we use?
  • The RookieThe Rookie Posts: 27,748
    The argument was about whether an MTB needed fluid changes, I said not as it is a sealed system (closed, not open to atmosphere etc etc whatever word you want to use), others said it wasn't sealed, then we had links to car pages about why you have to change fluid (not sealed systems), then we have the terminaology argument which as you say isn't relevant at all in itself unless it refers back to the hydroscopy/sealed argument but is being taken a long way by Ion who hasn't (despite being asked) sugegsted how it refers to the original discussion.
  • EH_RobEH_Rob Posts: 1,134
    now im not an engineer, however, i bled my xts the other week, they'd had about 12 months pretty heavy use and had gone a little bit spongy. i noticed a slight discoloration in the fluid coming out so decided to discard and replace. as far as im aware the system does not leak fluid from anywhere, and other than the sponginess i mentioned I have had no performance issues.

    surely in order for the fluid to never need replacement you would need a seal which is 100% impervious to everything all of the time, which sounds pretty far fetched. your little o-ring at the top of the system won't do that. It might stop a lot of gunk getting in there, but it won't stop everything.
  • levolonlevolon Posts: 78
    EH_Rob wrote:
    now im not an engineer, however, i bled my xts the other week, they'd had about 12 months pretty heavy use and had gone a little bit spongy. i noticed a slight discoloration in the fluid coming out so decided to discard and replace. as far as im aware the system does not leak fluid from anywhere, and other than the sponginess i mentioned I have had no performance issues.

    surely in order for the fluid to never need replacement you would need a seal which is 100% impervious to everything all of the time, which sounds pretty far fetched. your little o-ring at the top of the system won't do that. It might stop a lot of gunk getting in there, but it won't stop everything.


    and your not even an engineer ?? but you noticed that you brake fluid had become contaminated as it was discolored!!

    so you changed it and all good again.... yes it really is that simple

    beginner how many times do i need to say its hygroscopic and absorbs moisture for you to absorb it ffs

    i dont make brake fluid so as a manufacturer as your the engineered after all ?
  • The RookieThe Rookie Posts: 27,748
    FFS you haven't said where the moisture is coming from.....there is no direct path into the fluid system for it and you still, despite being asked several times, answered that. You did claim Osmosis, but of course viton isn't permeable.

    Of course moisture absorbption won't change the colour of the fluid, so Robs contamination wasn't that, also it is the Glycerol in normal brake fluid that is hygroscopoc and Rob's Shimano XT uses Mineral oil whch is significantly less hygroscopic, so Rob's tale is kind of irrelevant to the argument, despite you clutching desperately at the straw.
  • EH_RobEH_Rob Posts: 1,134
    FFS you haven't said where the moisture is coming from.....there is no direct path into the fluid system for it and you still, despite being asked several times, answered that. You did claim Osmosis, but of course viton isn't permeable.

    Of course moisture absorbption won't change the colour of the fluid, so Robs contamination wasn't that, also it is the Glycerol in normal brake fluid that is hygroscopoc and Rob's Shimano XT uses Mineral oil whch is significantly less hygroscopic, so Rob's tale is kind of irrelevant to the argument, despite you clutching desperately at the straw.

    if some general censored can get in (which I guess is what caused the off colour of the fluid), why not moisture?
  • levolonlevolon Posts: 78
    cyd190468 wrote:
    lon 456 wrote:
    go try this , go to bike and undo bleed half a turn and then pull lever to the bar AND hold it there ..
    nip up bleed nipple and then release the lever ... oh what do you know it is solid still!!!
    basic stuff this guys but if people read your advise on bleeding etc its no wonder they get it wrong...

    and when did we finally get the brake fluid thing then guys ?

    happy

    ive bled more brakes than i care to remember
    I did precisely as you requested and with my m596s after purging one complete pump of mineral oil from the system the lever came back to the bar because the reservoir only contains enough mineral oil to partially compensate for pad wear so the loss of one complete "lever pump" of fluid left the system underfilled.
    How many sets of mtb brakes have you bled? I have bled many sets of motorcycle and car brakes and they perform just as you suggest, however none of the mtb brakes I have worked on have a significant amount of fluid in the reservoir other than the ones on a mates 99 rocky mountan which were set up like motorcycle brakes, with a large reservoir with an airgap under the diaphragm.


    i have 2 sets of 596's thanks and avids and hayes and tecktro's

    would appear your system was very low on fluid then or you got it wrong again?? .. as it works fine on my 596's
    ill see if i can find a Janet & John brake guide for you..

    beginner YAWN
  • Chunkers1980Chunkers1980 Posts: 8,035
    Do you read who's posting this stuff?
  • Pesky JonesPesky Jones Posts: 2,986
    I think the arguement here lays with theory and practicality - theoretically moisture shouldn't get in. It does.
    :D:lol::)cooldad :shock: :? :cry:
  • Chunkers1980Chunkers1980 Posts: 8,035
    But how do you know moisture has got in?
  • Pesky JonesPesky Jones Posts: 2,986
    I have a 6th sense for when things start to get wet. Take that any way you want
    :D:lol::)cooldad :shock: :? :cry:
  • The RookieThe Rookie Posts: 27,748
    PMSL....if you say so!

    Rob, the contaminant may have been in there when built perhaps....or entered through the bleed nipple which do have a habit of getting crud in the orifice.
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