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Rear brake seized

Discussion in 'Technical and Troubleshooting Torque' started by Superunknown, Jan 21, 2008.

  1. My rear brake seized on me and i'm chasing some advice and info?

    Riding home from work was all normal until about 400m from home. I live on top of a fairly large, steepish hill. Normally I get a fairly brisk run up and cruise up at 60 in 4th. Today I go up to 4th and went for a bit… dropped down to 3rd with the throttle wide open and still slowing very slightly and thinking wtf? I though maybe I wasn’t used to the power having just done a big ride on my 650 a few days ago… dropped to 2nd and powered up the hill. Got to the top and stopped to see what was going on.

    The rear caliper was glowing red!

    Pulled over, jumped off and had a think. I couldn’t move the bike at all now. A friendly neighbour offer a helping hand and we agreed to go get my trailer and take my bike the 30m across the road to my house. After going home and changing went back outside and the wheel was now spinning freely but there was no resistance in the brake pedal. Now it just moves all the way though its travel very easily, but always returns to its usual position.

    What do you think happened? I have read a few other articles but most of them went (only just) over my head. Why after it cooled did the caliper free up, did the rotor contract enough to release as it cooled?

    Will this be an expensive fix or could I have a crack at it myself? I'm not totally retarded with tools, just inexperienced and slightly overcautious

    Could this have ruined the rotor (which I hear are expensive)?

    Will it be ok to ride to my mechanic? Will it heat back up and lock again?

    Thanks for reading guys

    +edit: The bike is a 2005 Hyo 250 Comet. 25,000 km's. New rear brake pads about 5-7000 km's ago installed by a professional mechanic. They have been squeeky at low speed since i got the new pads.
  2. Now that it has cooled down, does the rear brake actually work? When you press on it can you see the pads contact the disk? Do they return after you release the brake?

    What maintenance were you doing on the weekend before the brake locked up today?

    Did you adjust the brake lever position?

    When did you last use the rear brake on your ride home? Did it work properly? Did the bike seem sluggish after that?

    Do you listen to an mp3 player while you ride?

    All the best

    Trevor G

    PS If the rear wheel had caught on fire do you think you would have actually noticed before the brigade got there??? ;-)

    PPS It's probably not too bad - I know of people who continue driving after the water and/or oil lights have come on, until the engine is completely stuffed.
  3. At a guess sounds like it might have been due to water in the brake fluid - heat from braking turned it to steam which then pushed out the brake piston. You say the pads were changed recently but are you sure the brake fluid was changed (properly) too?
  4. Honestly i have no idea about whether the fluid was changed or not. Pads changed at ~16,000 or soon after. Got a 24,000 major service about 800km (>2 months) ago which i was told involved a change of brake fluid along with everything else. But in those 800kms i have done some fairly hard riding, much harder than the 10 min tootle home. Wouldn't it have shown up already?

    Sorry for omitting the major service and fluid change at 24,000km's.
  5. Recent major service as above. Didn't mess with anything myself since the service.

    brake does not work. pedal moves with very little or no resistance but nothing engages.

    The bike felt normal most of the way. I had a few stop starts and if the rear had seized up i think i would have noticed a handful of revs and major slippage of the clutch to get started (one would hope). IMO i think i picked up the problem fairly recently after it started, or at least once it got into the "very bad" category. Would have used the rear brake <1min before this seizure. and come to think of it, would/should have noticed no feedback in the pedal.

    Basically i think i would have noticed. No mp3. not weird sounds heard. just bad smell of burning brake pads once i stopped.
  6. I agree with Jd, thinking water in the brake fluid. And more then likely some serious brake drag.

    Sorry to say this but. If it was seriously glowing red, then that means heat over 200.C and the seals would have melted. That means either stripping the caliper and checking if its rebuildable, or a new caliper.
    Also its highly likely that your disc would have warped due to the heat and seizure.

    I would take it to the mechanic asap. Wouldnt advise riding it there, trailer to be safe. Most mechanic places will do pick ups.

    Good luck
  7. i had similiar on my RS i had brake drag caused my pads to wear out in 2 weeks than lock my caliper and weld the pistons to the (bare) pad

    i needed new seals & m/c as all the shit from the caliper catching fire f7cked that too

    hope that helps although its probably not what you want to hear.

    take it back to whoever serviced it
  8. I don't see any problem with riding it without a rear brake if you're just taking it to the mechanic's. Not sure of the cause, JD may well be right - but since it's recently been serviced and you'd generally expect the brakes to be bled properly, I'd be pushing to have the whole system replaced as a warranty claim. That includes the disc, 'cause like Natta said it may well have warped under that sort of heat.

    Go the Hyo!
  9. The odds are that the rear brake pedal position adjustment is wrong. A locknut or similar has quite possibly come loose, and the adjustment has "screwed itself up" gradually over a period.

    It gets so bad in the end that the fluid cannot return to allow the pads to come back off the disc.

    The brake no longer works now because either the piston(s) are seized, the fluid has leaked past faulty seals or the pads are worn out.

    This is the third such problem in as many weeks I have read about - the other two were pedal/rod adjustment issues.


    Trevor G
  10. Thanks guys.

    I'll take it to the mechanic this friday and see what he says. Hopefull he'll be honest about it all and admit his fault if he made one. He's been great so far.

    There is still a stack of fluid in the system... well, in the resivouir anyway.

    I'll let you guys know what it was.
  11. It was a faulty seal in the master cylinder. Hyosung do not sell just the master cylinder so i had to get a whole kit ordered in. So it's now got a brand new rear master cylinder, fluid reservoir and brake hose... all apparently redesigned since my bike was made.

    It cost alot for a seal about the size of a 5c piece. :evil:
  12. that sucks

    but how did you wear out the rear disc-pads in 16,000km?
  13. and did you get it under warranty?
  14. That's what Hyosungs do, OP is VERY lucky if Hyosung replace it, I have heard of this thingbefore with Hyo's, and teh owners were left high and dry.
    Another one for the "get a POS" files.

    Regards, Andrew.
  15. I bought the bike second hand with 14,000 km's on it. No idea what the guy before me was doing with it. I was told he sold the bike to get kidney treatment and rode it up here from Vic because Bris has the best specially equipped hospital... (good story? :p)

    Warranty has run out.

    +Edit. BTW, i don't regret buying the hyo. It was a good bike to learn on. It had not had any major faults until this. I put 11,000 km's on her. Now that i have had a spin on other bikes i realise the quality is not quite there, but for a learner it suited me fine.