675 Street Triple R 2014 - Weak Front Brakes

Discussion in 'Street Triple' started by Popkos, Oct 8, 2019.

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  1. Popkos

    Popkos New Member

    Aug 26, 2019
    7
    3
    Czech Republic
    #1 Popkos, Oct 8, 2019
    Last edited: Oct 8, 2019
    Hello,

    I´ve bought a 2014 Street Triple R about a month and a half ago with 39 000 km´s from new.
    Bike has ABS.
    When I got the bike, front brakes were fantastically sharp, only one finger was needed to stop.
    I´m now at 40 000 km´s, and front brakes started to feel very weak. You need more power and they aren´t sharp as before. They almost remind me of my old Kawasaki Z750 brakes, which were simply rubbish.

    The bike got a new brake fluid about a month ago, before I bought it (got invoice from service).
    Brake pads seems like they have a lot of meat remaining.
    What would you suggest?
    Get off the calipers, clean them with hot soapy water? Try to bleed the brakes? Or is this some common problem?

    PS: The rear brake is very weak too (it needs quite a lot of force to start braking when comparing with my old Z750).

    Thank you for advice.
     
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  2. PH1969

    PH1969 Well-Known Member

    Jan 6, 2017
    65
    78
    Northampton
    Still fluid in the resevoir?
     
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  3. Old phart phred

    Old phart phred Noble Member
    Subscriber

    Jun 23, 2019
    1,235
    443
    Ks
    Are the pads glazed?
     
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  4. Popkos

    Popkos New Member

    Aug 26, 2019
    7
    3
    Czech Republic
    Sorry, I did not understand your question. What do you mean by that? If is the fluid at the same level?
     
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  5. Popkos

    Popkos New Member

    Aug 26, 2019
    7
    3
    Czech Republic
    Haven´t checked the stripped calipers yet. What would that mean, if they are glazed?
    I have an invoice, that there are installed Brembo Sinter pads (07KA23SA).
     
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  6. PH1969

    PH1969 Well-Known Member

    Jan 6, 2017
    65
    78
    Northampton
    Is the fluid at the same level in the reservoir, is there any fluid in there? If the pads are good probably worth bleeding it through again.
     
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  7. Notso

    Notso Senior Member

    Dec 17, 2018
    328
    113
    Solihull
    Have you tried cleaning the disks with brake cleaner and a clean rag? I wonder if a spot of oil, grease, polish, acf50 etc. has got on there.

    Sorry if too obvious, that's about my limit of brake knowledge!
     
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  8. Callumity

    Callumity Elite Member

    Feb 25, 2017
    2,801
    750
    Nr Biggar
    There are two possible issues or a combination of both:

    Loss of clamping force
    or
    Loss of friction

    Either your hydraulic system is leaking/has air in it and is failing to transmit clamping force from pads to disc
    Or
    The pads/pins are partially seized from corrosion/contamination and/or the pads and disc surface have become contaminated or glazed.

    FIRST, while stationary, squeeze the brake lever. Does it feel firm or spongey? If spongey you have air in the system and your fluid change may be the culprit, especially if the ABS system got partially drained.

    Discs and pads can be roughed with fine sandpaper and wiped clean with brake cleaner or acetone. If you are not a competent mechanic find one! Brakes are not to be played with.
     
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  9. Popkos

    Popkos New Member

    Aug 26, 2019
    7
    3
    Czech Republic
    Thank you.

    Do you know, where the leak could be? I read about master cylinder failure (new piston kit should repair it).˝

    Or somewhere else? The bike has new fluid from this July.
     
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  10. darkman

    darkman Crème de la Crème

    Oct 26, 2015
    4,376
    1,000
    Southcoast of the UK Earth
    Caliper piston seized ??
     
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  11. Popkos

    Popkos New Member

    Aug 26, 2019
    7
    3
    Czech Republic
    #11 Popkos, Oct 20, 2019
    Last edited: Oct 20, 2019
    So Today I managed to strip the calipers. Looked pretty dirty, probably never been cleaned. Pads were changed once. I cleaned the calipers and tried to pump levers and look for seized piston. The bigger pistons were moving freely and on every side the one piston from the smaller duo was a bit stuck. I got them moving by pumping and pressing them back in.
    I did not have time to test ride the bike sadly, so don’t know, if it helped yet, but as someone mentioned above, the lever feels a bit spongy, so next up is brake fluid change + bleed. I don’t have diagnostics or OBD and TuneECU app, so can’t bleed the abs, but if is the lever spongy, than the air must be between master cylinder and calipers I think. Strange, that the fluid has been changed two months ago.. here are some photos from the action
    20191019_123730402_iOS.jpg 20191019_125442070_iOS.jpg 20191019_131210150_iOS.jpg 20191019_131503071_iOS.jpg 20191019_132809086_iOS.jpg

    20191019_133317060_iOS.jpg
     
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  12. Popkos

    Popkos New Member

    Aug 26, 2019
    7
    3
    Czech Republic
    So I´ve ridden the bike and.. well sometimes the brakes feel very nice and sometimes they feel very week.. depends on situation. Very strange.
    I took of the front lever to check the master cylinder piston seal, but it looks like its fine. No sign of any leaks.

    It is now cold outside, so I will probably continue this mission next year, cuz the bike will be sleeping over winter :D

    Next thing to do is the brake fluid change/bleed.
    unnamed.jpg
     
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  13. capt

    capt Noble Member

    May 8, 2016
    2,011
    450
    western Australia
    You may still have dirt in one of the caliper pistons , when it move's out you have good brakes ! When it moves back in it binds and you have poor brakes ! Piston's will '"jam'" on the smallest bit of dirt if its in the right position !
     
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  14. Popkos

    Popkos New Member

    Aug 26, 2019
    7
    3
    Czech Republic
    So what you suggest? Tak them off again a clean them one more time?
     
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  15. capt

    capt Noble Member

    May 8, 2016
    2,011
    450
    western Australia
    If as you say you are laying up the bike for winter , pull the brake system apart . use low air pressure to 'pop' the piston's out , put something wood or plastic between the piston's. When completely apart clean everything , use mineral turps or or kerosene as cleaning fluid. You can polish the piston's with tooth paste (its very fine,non abrasive to metals) blow everything dry and then put it back together using small amount of rubber grease , work the piston's back and forth to check smooth action (low air pressure) use the wood again ! When happy it's all good you are ready to reassemble.
     
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  16. Popkos

    Popkos New Member

    Aug 26, 2019
    7
    3
    Czech Republic
    Hello again guys..

    I was just thinking again about the situation with weak front brakes.

    Is there any chance that air can get from the ABS module to the front brake circuit?

    Because when I got the bike, I tried to block rear end wheel, to know, how the ABS behave and I think, that the FRONT brakes got worse after ABS was handling the blocked rear wheel.. But again, I´m not 100% sure.. just asking, if is this possible or not.
     
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  17. Callumity

    Callumity Elite Member

    Feb 25, 2017
    2,801
    750
    Nr Biggar
    .......yes. Your ABS is a pump/modulator unit that reacts to a pulse signal from the rotation. When it senses lock up it reduces hydraulic pressure via the ABS unit. If you have air in the ABS module then actuating it will re-introduce air to a bled system.
     
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  18. Popkos

    Popkos New Member

    Aug 26, 2019
    7
    3
    Czech Republic
    And if I blocked the rear wheel, is it possible that air would get to the front brakes system?
     
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  19. Callumity

    Callumity Elite Member

    Feb 25, 2017
    2,801
    750
    Nr Biggar
    Well........ are they linked? (No!)
     
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  20. joe mc donald

    Subscriber

    Dec 26, 2014
    9,474
    1,000
    slough / burnham
    Popkos
    Just a thought how full are you reservoirs as they also need a little space in there to function properly.
    Regards
    Joe.
     
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