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Thread: new brake pads and brake fluid

  1. #1
    Flirting With The Redline dpwell's Avatar
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    new brake pads and brake fluid

    hi - I'm shortly going to install new front brake pads. Do I need to do anything with the brake fluid? There's a somewhat confusing instruction sheet that came with the new Honda pads that says "the upper/lower level line of the reserve tank indicator is designed to set the fluid levels on the precondition that the pad is still new. Therefore when you replace the brake fluid, please adjust the fluid level to the upper level line". I'm not sure what they're getting at here. What if you are replacing the fluid and your pads are not new? What if you're installing new pads and your fluid was replaced a year ago?
    2018 Honda CRF250L ('Rhonda')
    2015 Honda CB500X ('Betty')
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  2. #2
    RiderCoach 4000 Posts! AZridered's Avatar
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    When the pads are brand new, the fluid level should be a the upper line. As the pads wear, the line will drop as the brake pistons (which push the pads) extend farther and farther.

  3. #3
    This is a pet peeve of mine. If you need to add brake fluid, your pads are low or you have a leak. Fix the problem, don't just add fluid. So to answer the question, no, there is no need to add brake fluid during a normal pad change.
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  4. #4
    Flirting With The Redline 8000 Posts! Trials's Avatar
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    Quote Originally Posted by dpwell View Post
    .... What if you are replacing the fluid and your pads are not new?...
    Push the pads apart as far as they go, that is where your brake pad travel starts and where the reservoir should be well up on the full mark line.

    ... you have to do that anyway to get all the old fluid out of the brake calliper when doing a fluid change.

  5. #5
    RiderCoach 5000 Posts! NORTY's Avatar
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    Quote Originally Posted by dpwell View Post
    What if you are replacing the fluid and your pads are not new?
    As AZridered stated, since your pads will wear, this wear will displace fluid from the M/C. There isn't much reason to change the fluid without changing the pads. But, if you do want to change fluid, then replicate the fluid level in your M/C with the new fluid.
    What if you're installing new pads and your fluid was replaced a year ago?
    1 year old fluid is likely ok, unless you live in a humid environment and the M/C lid has been open a lot. Some brake fluids are "hygroscopic". This means they'll literally "pull" humidity right out of the air. The fluid will then "hold" the water in suspension. This water may corrode things within the brake system components. Water may also breakdown constituents built in the brake fluid. Water DOES compress slightly, causing a mushy lever or pedal. Water when heated enough may turn to steam, causing a mushy pedal/lever. It can also cause the volume of fluid to expand, causing the pads/shoes to force themselves against the rotor/drum, even without the application of lever or pedal. It tries to create an "interference" fit, making even more heat and pushing the pads/shoes even harder to their swept surfaces.
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  6. #6
    Flirting With The Redline dpwell's Avatar
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    Quote Originally Posted by NORTY View Post
    There isn't much reason to change the fluid without changing the pads.
    Not sure I follow that. Next Spring my brake fluid will be around 2 years old and need to be replaced, while my brake pads may still have loads of life left, especially the rear, which seems to be taking forever to wear out. It would seem silly to replace perfectly good pads, especially given how costly they are.
    2018 Honda CRF250L ('Rhonda')
    2015 Honda CB500X ('Betty')
    Previous bikes:
    2009 Ninja 250 ('Saki')
    2007 Honda CBR125
    http://www.vancouvermusictheory.com

  7. #7
    RiderCoach 5000 Posts! NORTY's Avatar
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    Quote Originally Posted by dpwell View Post
    Not sure I follow that. Next Spring my brake fluid will be around 2 years old and need to be replaced, while my brake pads may still have loads of life left, especially the rear, which seems to be taking forever to wear out. It would seem silly to replace perfectly good pads, especially given how costly they are.
    With this add'l info, you are correct. For some riders though, brake pads are done in 10,000 miles, which can be burned thru in 2 months here. Some ride a little, some ride a lot.
    Knowledge speaks, wisdom listens.

  8. #8
    RiderCoach 4000 Posts! AZridered's Avatar
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    When brake fluid is flushed and changed, the pistons should be pushed fully into the calipers. This forces old brake fluid out of the caliper bores (places that moisture is likely to collect). When this is done, just refill the master cylinder and pump the pads back into contact with the discs. Your fluid will drop to the correct level.

    The exception is some bikes which may have been styled with smaller than full capacity brake fluid reservoirs. These may need fluid to be added before the pads are fully worn down.

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