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  1. #1
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    When to bleed brakes

    I've heard that brakes should be bled once a year. Is that true?

  2. #2
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    I've heard people that do that, but never mess with it unless there are symptoms.

  3. #3
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    I have a pair of Shimano's that haven't been bled since they were installed in 2001. Still Work fine.
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  4. #4
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    I'm sure the once a year rule was devised by the marketing teams.

  5. #5
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    My name is MikeDee and I get respect
    When to bleed brakes is what I expect
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  6. #6
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    I assume it depends on if you use mineral oil or DOT fluid. DOT should be bled annually, or maybe 2 years since it attracts water that lowers the boiling point.

    For mineral oil I wouldn't worry before maybe 5 years unless you have a strong reason you overheated the oil a lot (unlikely since you then also had discolored rotors etc.). Maybe check the fluid if you really ride and brake hard and often.

    Over time some dirt will pass through the seals, so dark fluid would be an indicator of need for a full bleed.

    Obviously bleed out some air if they are spongy.
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  7. #7
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    You bleed them when they start to feel mushy/spongy or you feel that something is wrong. Otherwise don't mess with working brakes if they work as expected, no gain there.

  8. #8
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    It's been almost a year since I last bled my brakes (DOT fluid). I'm about to put new pads and larger rotors in. I guess I should probably bleed the brakes while I've got the system somewhat disassembled. Not my favorite maintenance activity though.

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    Personally I bleed when replacing pads. Itís easy, gives me a great opportunity to clean and lubricate the pistons, and ensures trouble free operation. Itís all very depending on equipment and riding conditions though, your Shimano mineral oil might last 10 years or 10 hours. Iíve blackened (overheated) fluid in a couple weeks of hard trail riding with brakes a little undersized for me before.

  10. #10
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    When to bleed brakes

    My street motorcycle has 3 discs each with 3 pistons. The front and rear are interconnected with a proportioning valve and three master cylinders.
    Bleeding those is a maintenance chore.

    Bleeding my mtb brakes seems a breeze compared to my motorcycle.


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  11. #11
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    Quote Originally Posted by MikeDee View Post
    It's been almost a year since I last bled my brakes (DOT fluid). I'm about to put new pads and larger rotors in. I guess I should probably bleed the brakes while I've got the system somewhat disassembled. Not my favorite maintenance activity though.
    I still wouldn't bother if they're working properly. Clean the calipers up with alcohol before pushing the pistons back to keep the gunk out of the seals. Bed in the new setup. If it works, run with it. If not, then it's time for a bleed.

  12. #12
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    Yup. Clean meticulously and bleed 'em at least once a year. Fluid becomes contaminated with moisture and dirt, and dissolved air comes out of solution. Granted, modern brakes are really great and will often continue to function for the life of me bike with little maintenance, but if you want tip-top performance you need to make a little effort. It's like buying a new Camry. You can drive it for 150,000 miles with no maintenance, but driving it won't be nearly as nice an experience as Ūf you kept it tuned up.

  13. #13
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    Quote Originally Posted by WHALENARD View Post
    My name is MikeDee and I get respect
    When to bleed brakes is what I expect
    I laughed pretty hard at this.

    Quote Originally Posted by farfromovin View Post
    Personally I bleed when replacing pads. Itís easy, gives me a great opportunity to clean and lubricate the pistons, and ensures trouble free operation. Itís all very depending on equipment and riding conditions though, your Shimano mineral oil might last 10 years or 10 hours. Iíve blackened (overheated) fluid in a couple weeks of hard trail riding with brakes a little undersized for me before.
    I agree with this. If the brakes go off before the pads are done, then I bleed. Otherwise not until swapping pads.

    That said, I don't have a DH rig ridden in wet conditions. If you have that, then pad life is radically different.

  14. #14
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    I went ahead and bled the brakes. The front brake had some air that came out. Funny that the brake lever wasn't mushy or had excessive travel. It must have been in the reservoir.

  15. #15
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    Keep in mind that DOT fluid can only absorb moisture if it's exposed to the air.

    In a sealed up brake it can't.
    In a vehicle master cylinder reservoir it's exposed to air and can.
    Ridden in wet conditions it's possible to track moisture in through seals.

    Conditions matter, age doesn't really.
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  16. #16
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    Personally, I'm going to get into the habit of doing it more often. It's been maybe 5-6 months since I last bled my XTR Trail brakes and this is what I got:



    I've also have experienced what I'll just call "issues" at the brake lever that I've convinced myself coulda been avoided with a shorter bleed intervals. Sticky/stuck levers and leaks... perhaps from a breakdown of the seals and contamination of the lever piston.

    Shimano mineral oil isn't that expensive when you buy the big bottle (divided by the number of bleeds you'll get), the caliper pistons will be happier, it's easy to do, I always notice an improved feel after a needed bleed, and it gives me something to do while I drink beer.
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  17. #17
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    Mmm, looks like a chocolate shake. I flushed my m8000ís after a month of thrashing them and it was much darker than new fluid, but not frothy looking like that! Amazing they still function really.

  18. #18
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    Quote Originally Posted by teamdicky View Post
    Personally, I'm going to get into the habit of doing it more often. It's been maybe 5-6 months since I last bled my XTR Trail brakes and this is what I got:



    I've also have experienced what I'll just call "issues" at the brake lever that I've convinced myself coulda been avoided with a shorter bleed intervals. Sticky/stuck levers and leaks... perhaps from a breakdown of the seals and contamination of the lever piston.

    Shimano mineral oil isn't that expensive when you buy the big bottle (divided by the number of bleeds you'll get), the caliper pistons will be happier, it's easy to do, I always notice an improved feel after a needed bleed, and it gives me something to do while I drink beer.
    That's nasty. Is it from the lever or has it been pushed up from the caliper? If it's caliper I'd drain it out the bottom rather than pushing it up through.
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