Rear Brake Nonsense With The Bonneville

Discussion in 'Technical Help' started by steve lovatt, May 5, 2018.

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  1. steve lovatt

    steve lovatt Something else

    May 12, 2014
    9,211
    1,000
    North Yorkshire
    Sun was out and due to meet up with friends at their house around 20 miles away - "are you taking the bike" she says (the answer is obvious) "I'll come with you" she says. This would be the first time since last September - the bike has been fine and I was out on it twice on Thursday.

    Less than a mile form our destination and at around 35 mph, the bike suddenly feels as if you've shifted up from 2nd gear to 5th by mistake and runs like an absolute pig. I shift down to 3rd and then 2nd but it still runs badly but by and then we're at the turn anyway so come off the main road and prepare to stop but it suddenly picks up OK so we go on another 300 yards to the house.

    Get off the bike and the rear brakes are smokin' big time - the disc is actually blue. Leave it all to cool down and then take a look. On the centre stand and I can barely turn the rear wheel by hand and the brake pedal is almost solid when you try and push down on it. I manage to get one pad retaining pin out with my limited tool kit but the other one rounds off!

    Thankfully borrow a socket set and a set of hex keys and have the caliper off. The pistons are seized solid and nothing is moving so not much else I can do. Unbolted the banjo nut and no fluid comes out. Get a jar and pump the pedal and eventually with a "gush" all the fluid comes out and the pedal is free. Rode home with caliper in the rucksack and the hose cable tied up to the frame.

    Looks like I could need a new disc, will need to drill one pin out of the caliper and then if it's salvageable a seal kit and new pistons probably. Going to look at it properly this morning. May now consider the Motone caliper relocation bracket as well!

    By the way - World of Triumph want £405.00 for a new caliper and £143.00 for a new disc, plus £64.21 for new pistons and £24.22 for the seals! (plus postage of course).

    20180505_085352.jpg
    Doesn't really look blue here (but it is)
    20180505_085345.jpg
    How to get home!
     
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  2. Oldyam

    Oldyam Grumpy Old Git

    May 14, 2017
    613
    500
    ireland
    Sounds like the rear brake line has failed and needs replacing, then strip and check everything else, replace as needed.
     
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  3. MrOrange

    MrOrange Guest

    Sounds like a seized caliper. Strip, clean, new seals, plenty of RRG on assembly.
    Can you get the disk skimmed? Enough meat left on it?
     
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  4. steve lovatt

    steve lovatt Something else

    May 12, 2014
    9,211
    1,000
    North Yorkshire
    Caliper is OK - cleaned up well and old retaining pin is now drilled out! Pistons pushed back in by hand so they probably aren't seized - suspect the brake hose!
    Ordered new one and new pins and will check the disc to see if it isn't warped.
     
  5. MrOrange

    MrOrange Guest

    How does the hose fail and lock the brake on?
     
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  6. Sprinter

    Sprinter Kinigit

    Aug 17, 2014
    6,026
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    uk
    WTF? " Get a jar and pump the pedal and eventually with a "gush" all the fluid comes out and the pedal is free." I cant think what would cause that, even if its a blockage where did it come from?
    Do you think youll solve it?
     
  7. Erling

    Erling Elite Member

    Dec 12, 2017
    1,123
    943
    Norway
    What might have happened, is that the internals of the brake hose have collapsed making the hose act like a check valve.
     
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  8. MrOrange

    MrOrange Guest

    If it was locked on, would fluid then boil and empty out of caliper ?

    Can only think that piston or pins seized enough to jam the brakes on. Then cause other troubles, imho.

    Ti's all guess work at the end of the day. But least likely culprit would be the hose I would have thought
     
  9. tcbandituk

    Subscriber

    Apr 8, 2016
    2,763
    1,000
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    My guess (and it's just a guess:)) would be the rear brake was used a bit more with a pillion, the pads heated up and, being a bit thicker due to being new*, expanded, locked on and caused the fluid to boil?

    If that was the case, you're lucky it didn't just seize on, I've seen a guy pitched from his Busa with a similar problem.

    *IIRC, you've not long replaced them?
     
  10. Callumity

    Callumity Elite Member

    Feb 25, 2017
    3,358
    800
    Nr Biggar
    Brave of Steve to post photographs......the chain and sprocket don’t shriek maintenance ;)

    I’ll get my coat.....

    (Mine looked like that til last week....winter etc....)
     
  11. Hack Driver

    Hack Driver Well-Known Member

    Oct 12, 2017
    455
    63
    Denton, Maryland USA
    My compliments - I'm not sure I would have been smart enough to take the caliper off and ride home without calling for a tow. In addition to the items listed above (bad hose, pistons seized in the caliper, additional stress) you might think about the piston set in the rear brake master cylinder. It may be contaminated or have some other problem which would have caused the caliper to seize. Then with repeated pumping, it might have 'freed-up' and pushed the remaining fluid in the line out of the banjo fitting. The rest of the fluid could have been in the caliper due to it's expansion. This doesn't explain why no fluid was in the line when you took it off initially.
     
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  12. steve lovatt

    steve lovatt Something else

    May 12, 2014
    9,211
    1,000
    North Yorkshire
    It's much cleaner than it looks and covered in WD40 chain wax. Unfortunately after a couple of days it makes the chain look rusty!
     
  13. steve lovatt

    steve lovatt Something else

    May 12, 2014
    9,211
    1,000
    North Yorkshire
    No not that long ago - same day I met you and crispey at Loomies :cool:
     
  14. steve lovatt

    steve lovatt Something else

    May 12, 2014
    9,211
    1,000
    North Yorkshire
    More investigation needed I think. Haven't had the hose off yet but will look at that tomorrow!
     
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  15. Callumity

    Callumity Elite Member

    Feb 25, 2017
    3,358
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    Nr Biggar
    No, mine was genuinely filthy!
     
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  16. steve lovatt

    steve lovatt Something else

    May 12, 2014
    9,211
    1,000
    North Yorkshire
    That was my thought as it seemed as if the brake were locked on and as I now know the piston move freely.
     
  17. steve lovatt

    steve lovatt Something else

    May 12, 2014
    9,211
    1,000
    North Yorkshire
    Slightly glazed pads and remains of the retaining pin.

    20180505_130027.jpg 20180505_130036.jpg
     
  18. stevethegoolie

    stevethegoolie Elite Member

    Oct 16, 2014
    2,452
    800
    East Riding of Yorkshire
    They are buggered, they are!:eek:
     
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  19. Yorkshireman

    Yorkshireman Crème de la Crème

    Dec 12, 2015
    3,401
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    Barnsley
    That’s what I would point the finger at given your explanation.
     
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  20. MrOrange

    MrOrange Guest

    I'm not following how a tube fails, then becomes something more?
     
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