when do you need to bleed hydraulic brakes?

Giraffoto
Giraffoto Posts: 2,078
edited February 2012 in The hub
This is a slightly techie question, but I’m posting it here because it’s more for my curiosity than to solve anything I’m planning to do. So, when do people really need to bleed hydraulic brakes? On a car it gets done when the brake fluid gets replaced, is it needed more often than that on a bike? I’m curious about this because the number of threads on the subject suggests that there are people out there doing it every week for a bit of fun
Specialized Roubaix Elite 2015
XM-057 rigid 29er

Comments

  • 1mancity2
    1mancity2 Posts: 2,355
    once in 2 years on my brakes.
    Finished, Check out my custom Giant Reign 2010
    Dirt Jumper Dmr Sidekick2
  • if/when they feel like cack and under perform despite changine pads and cleaning etc
  • nicklouse
    nicklouse Posts: 50,675
    When the fluid has been contaminated or boiled. So that means rarely.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Anonymous
    Anonymous Posts: 79,667
    Indeed. Far less than people assume and don't blindly follow advice of "oh you need to bleed them mate".
  • VWsurfbum
    VWsurfbum Posts: 7,881
    hydroscopic fluid goes off at approx 2 years, so i would suggest then but even so thats only because its absorbed a lot of moisture and would boil easier, depends how hot you get your brakes?
    Kazza the Tranny
    Now for sale Fatty
  • Redhog14
    Redhog14 Posts: 1,377
    What are hydraulic brakes?
  • The Rookie
    The Rookie Posts: 27,812
    VWsurfbum wrote:
    hydroscopic fluid goes off at approx 2 years, so i would suggest then but even so thats only because its absorbed a lot of moisture and would boil easier, depends how hot you get your brakes?
    As most (all?) bike brakes are sealed systems, the fluid being hydroscopic is irrelevant as no moisture should be getting in in the first place.....unlike car/motorbike system that runs a ventilated master cylinder.

    Simon
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • VWsurfbum
    VWsurfbum Posts: 7,881
    VWsurfbum wrote:
    hydroscopic fluid goes off at approx 2 years, so i would suggest then but even so thats only because its absorbed a lot of moisture and would boil easier, depends how hot you get your brakes?
    As most (all?) bike brakes are sealed systems, the fluid being hydroscopic is irrelevant as no moisture should be getting in in the first place.....unlike car/motorbike system that runs a ventilated master cylinder.

    Simon
    True to a point.
    it still goes off with age. just like a tin of baked beans :wink:
    Kazza the Tranny
    Now for sale Fatty
  • The Rookie
    The Rookie Posts: 27,812
    No, it ages due to water/contaminants and oxidation, a sealed system will exhaust those in the first month or so, after that, no effect.

    So not true to a point, just true!

    Tins of baked beans from the 70's have been opened and found to have the contents in perfect condition......although I havn't tried the tin of Salmon I found that is priced in Shillings and pence......it hasn't 'blown' the tin though!

    Simon
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • VWsurfbum
    VWsurfbum Posts: 7,881
    Sorry but i disagree.

    Tinned fish is bad at the best of times, maybe take it to antiques roadshow :lol:
    Kazza the Tranny
    Now for sale Fatty
  • Anonymous
    Anonymous Posts: 79,667
    Tinned anchovies are best at any time, off or not. Though so much salt not sure they can go off. Anyway, great on Pizza :D
  • The Rookie
    The Rookie Posts: 27,812
    As someone allergic to any seafood, I have to disagree!

    Simon
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.