This brake Lever is getting a bit Squishy...- Mtbr.com
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  1. #1
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    This brake Lever is getting a bit Squishy...

    Out for a normal ride and I'm beginning to notice the brake lever is getting squishy. I get home and I'm thinking my rear brake has been compromised and I find this at the banjo and caliper. A blister in the hose at the banjo fitting. Shimano M-785's

    Anyone seen this happen before?

    Attached Thumbnails Attached Thumbnails This brake Lever is getting a bit Squishy...-20200521_143242-i.jpg  

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  2. #2
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    Nope! Was there any weird bends after the banjo? Possibly snagged on something during the ride?


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  3. #3
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    Nope, no previously weird or exceeded bend radius. It has never been snagged that I'm aware of. It was pretty tightly tucked under the seat stay. It appears slightly bent now because I bent it back to look at the failure point deeper into the crimp seal of the banjo.
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  4. #4
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    It looks like it's been heated. Do you carry the bike on rack that runs close to the exhaust?

    Tim

  5. #5
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    Nope, never been on a rack or near heat. I know about that one.
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  6. #6
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    Typical JRA PFM. Time for a new hose.
    Do the math.

  7. #7
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    Ok, I'll take the bait... what's JRA PMF?

    I'm assuming PMF isn't the mathematical Probability Mass Function.
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  8. #8
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    Just riding along...pre mature failure?

    I'd just trim it off if you have spare length.

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  9. #9
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    I'm not aware of anyway to trim at the banjo end of the fitting, it could be time for a whole new line unfortunately. Goodridge hose time!
    Silly bike things happening.

  10. #10
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    It just slowly became squishier Like a brake line aneurysm.
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  11. #11
    Mudhorse
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    Looks like cumulative damage from flexing. Full squish bike with externally routed rear brake hose? If so, a re-termination of the hose to the banjo bolt and some clever cable clamping will minimise the risk of a reoccurrence: clamp it solidly near the caliper, and clamp it more loosely on the main frame so the rest of the hose can move with the suspension.

    I've never had this on a brake line but it's a perennial issue with my Reverb seatpost on Winter Bike. I just have to keep an eye on it and re-terminate when it starts to look too dodgy.
    Hose me down till the water runs clear.

  12. #12
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    ^^^^ Nope, I don't think this was an issue. See post #3. The brake line at the Banjo show no signs of any flexing or having been snagged or bent. I bent it back at the banjo trying to look deeper into where the line was crimped. The origin of the brake line blister appears to be right at the crimp. The brake line was tucked in tightly and run under the seat stay all the way to the caliper and there were no signs of contact with anything.
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  13. #13
    Mudhorse
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    ^ Hmmm... if there's no way for the hose to flex then maybe it's melted. Do you do long downhill runs where you have to drag the rear brake? Shimano mineral oil brakes don't like getting hot (hence the pad option with the radiator fins). That said, bit of a long shot.

    You might be able to re-terminate the banjo by unscrewing the collar. If you try this, best to remove the banjo bolt from the caliper first as if the collar is seized then the banjo will shear in two - better to ruin an already knacked banjo than ruin a banjo and a caliper. If you do get the collar off then I reckon you can re-use the olive, just note which way round it went so you can put it back facing the same way.
    Hose me down till the water runs clear.

  14. #14
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    No excessive heat.

    I think it was just fluke. Sh!t happens. A replacement brake line, a quick bleed and all should be well. I was just curious if anyone here had seen this before.
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  15. #15
    Mudhorse
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    Quote Originally Posted by Cleared2land View Post
    No excessive heat.

    I think it was just fluke. Sh!t happens. A replacement brake line, a quick bleed and all should be well. I was just curious if anyone here had seen this before.
    I've only seen damage to the hose/banjo connection due to repeated flexing, though I'm sure other failure modes are available. If it's not that, and it's not heat from the brakes (yeah, bit unlikely, that) then maybe the person who mated the banjo to the hose used a bit too much heat to soften the end up and it's weakened the plastic in that area. There's no reason why a hose should fail right there if it's intrinsically faulty.

    I had an issue with a leaking Shimano hose on Summer Bike, right where it joins the lever. What I thought was a mangled white plastic grommet turned out to be silicone sealant that the bike assembler had bodged on. I found out why - they'd done a bad job of fitting the barb and olive, and instead of re-terminating and trying again they just slapped a bit of gunk on to seal it just long enough so that it wasn't their problem any more. It wouldn't surprise me if a hose assembler heats up the hose end so it's easier to shove onto the banjo barb, and it wouldn't surprise me if every now and then a hose gets overcooked. It would surprise me if this happened in the Shimano factory though. I've got a love/hate relationship with Shimano, but I will concede that their quality control is very good.
    Hose me down till the water runs clear.

  16. #16
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    JRA = Just Riding Around
    PFM = Pure F-ing Magic
    Do the math.

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