Problem with Hope E4 brakes

sandy771
sandy771 Posts: 368
edited November 2017 in MTB workshop & tech
I have an odd problem with my E4's

I changed the brake pads earlier and while the old pads were out I pushed back all four cylinders so the disk would fit (as I have done plenty of times before). When the new pads were in and I squeeze the brake lever nothing happens, or rather the pads move slightly but exert no real grip on the disk.

I didn't think it would be a fluid issue as I didn't lose any, but I bled the brakes anyway, but have the same issue :(

Anyone have any ideas what I may have done (wrong).

Comments

  • 02gf74
    02gf74 Posts: 1,168
    If you pull the lever and pads move but lever feels spongy then there is air in system

    If lever moves with little resistance then likely the piston seal in the lever is worn.

    There are stories of the seal lip being reversed which may have happened due to piston being pushed back when calliper pistons pushed in.

    Try bleeding again, if no joy you need to take lever apart to see what is going on.
  • The Rookie
    The Rookie Posts: 27,812
    If you see the pads come out each time you pull the lever and then retract the seals aren't allowing them to advance properly.
    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.
  • sandy771
    sandy771 Posts: 368
    Thanks for the feedback.

    I'll try bleeding again.
    There are stories of the seal lip being reversed which may have happened due to piston being pushed back when calliper pistons pushed in.

    I don't understand what I should be looking for, or what I can do about this - can you expand on it please?

    cheers
  • 02gf74
    02gf74 Posts: 1,168
    ^^^^^ I heard this happen with car brake master cylinders so as bike brakes work on same principle it could also happen.

    I'll try to to explain without a picture.
    <
    The above top and bottom lines are the bore and the line with < is the seal in cross section.
    Applying the bake pushes piston and seal to right. The edges of < touch the bore and due to their shape, the fluid presses against the edves forcing the lip against the bore making a tighter seal.

    Lip reversal the seal is > so the fluid presses in on it forcing the seal lips away from the bore.
  • sandy771
    sandy771 Posts: 368
    Thank You that makes sense.

    I think it's back to LBS with this one, changed the pads before without a problem strange this should happen now. They are still in warranty though.

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