Rear brakes
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Thread: Rear brakes

  1. #1
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    Rear brakes

    Since buying my bike used, I noticed the rear brakes gave no feed back.
    IE when applying the rear brakes, I can't tell how much rear brake I am applying.
    With the front, you know when the pads are grabbing.

    I went and bled the rear brake thinking there might have been some air in there. But after bleeding the brakes, it is still the same. No feed back.

    I noticed a lot of wear on the rear disk and the rear pads are down to less than 50%.

    Since I am heading to the 2F trackday on saturday, this doesn't leave me with a lot of time to play with the bike.
    And since Monday no one locally is open, that really puts me in a pinch.

    So I am here to ask for people's opinion. Is the rear master cylinder dead or a seized rear caliper?
    01 QX4 tow rig
    07 600RR track bike

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  3. #2
    Registered User Array FunJimmy's Avatar
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    It's difficult to diagnose a problem without physically looking it over.
    I'd suggest pulling the caliper, activating the brake pedal and confirming piston movement.
    You might also want to change the pads and lightly sand the rotor to deglaze it.
    I'm a fan of EBC pads. Readily available too.

  4. #3
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    In all honesty, I've never felt that the rear brakes on a sport bike gave great feedback at all. It's also a lot harder to modulate the pedal vs a lever. If they operate on a stand, they'll operate in use unless like you said you have air in the system or they're actually fading.

  5. #4
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    I had the bike up on the stand and activating the pedal by hand, there is no feed back. With the front brakes, when you apply the lever, you can tell when the pads are hitting the rotor as the lever gets stiffer.
    Same thing on your car when you apply the brakes.

    Right now, the rear brakes feel like the brakes on the car when you apply brakes with the car off.

    When I bled the brakes, there was good pressure and the pedal released like it should which is leading me to believe the rear caliper might be seized, which I hope isn't the problem.
    01 QX4 tow rig
    07 600RR track bike

  6. #5
    Registered User Array FunJimmy's Avatar
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    If you've got the bike on the stand and spin the rear wheel, can you stop it with the brakes?
    That simple test will tell you if the pads are contacting the rotor.

  7. #6
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    Does the calliper actually engage? Otherwise you still might have air in the system or your master is shot. A seized piston will have the opposite effect and build pressure in the system.

  8. #7
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    Fuck you fun jimmy. Lol.

  9. #8
    Registered User Array bandito's Avatar
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    You probably have increased rotor and pad wear because your caliper seals are degraded and not relaxing the piston/pads away from the rotor when disengaged.
    That is why you are not feeling the pads engage.

    Far more likely it's that, than it is a bunked master cylinder. Check the rotor is in spec, and orders piston/seals and some new pads and banjo washers if you like. Rebuild the caliper and
    I think you will find your problem is solved.

    You can get all of those parts ordered on Tuesday for Thursday and do the rebuild Thursday night.

    Just my opinion.
    Last edited by bandito; 06-15-2014 at 02:15 PM.
    Long Live Shervin Of The North!

  10. #9
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    Quote Originally Posted by bandito View Post
    You probably have increased rotor and pad wear because your caliper seals are degraded and not relaxing the piston/pads away from the rotor when disengaged.
    That is why you are not feeling the pads engage.

    Far more likely it's that, than it is a bunked master cylinder. Check the rotor is in spec, and orders piston/seals and some new pads and banjo washers if you like. Rebuild the caliper and
    I think you will find your problem is solved.

    You can get all of those parts ordered on Tuesday for Thursday and do the rebuild Thursday night.

    Just my opinion.
    Thanks. That sounds exactly like my problem.
    The MC would release like it should when I was bleeding the brakes so I think you are right.
    Luckily for me, the rear rotor is still in spec so all I need to do is rebuild the caliper.
    01 QX4 tow rig
    07 600RR track bike

  11. #10
    Registered User Array bandito's Avatar
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    Quote Originally Posted by SumAznGuy View Post
    Thanks. That sounds exactly like my problem.
    The MC would release like it should when I was bleeding the brakes so I think you are right.
    Luckily for me, the rear rotor is still in spec so all I need to do is rebuild the caliper.
    The piston is not cheap.... and may not be necessary.. but you don't know until you get it all apart. Personally, if I am going to the work to rebuild it, I pay the extra $35-$50 or whatever it will be for the piston just to be done.

    You can clean the caliper with isopropyl alcohol and let it dry out. If you haven't done it before... use brake fluid on the seals before installation and also on the piston before popping it in.

    If you are at all not sure about doing the job, get someone who does to help you... only because it's potentially a huge safety issue if you get it wrong. (Not that I don't think you can do the job).
    Long Live Shervin Of The North!

  12. #11
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    Quote Originally Posted by SumAznGuy View Post
    Since buying my bike used, I noticed the rear brakes gave no feed back.
    IE when applying the rear brakes, I can't tell how much rear brake I am applying.
    With the front, you know when the pads are grabbing.

    I went and bled the rear brake thinking there might have been some air in there. But after bleeding the brakes, it is still the same. No feed back.

    I noticed a lot of wear on the rear disk and the rear pads are down to less than 50%.

    Since I am heading to the 2F trackday on saturday, this doesn't leave me with a lot of time to play with the bike.
    And since Monday no one locally is open, that really puts me in a pinch.

    So I am here to ask for people's opinion. Is the rear master cylinder dead or a seized rear caliper?
    Rear brake use without a passenger on board... A really novel concept. Seriously, though. Probably the piston seized from compLete lack of use. Like I ride...

  13. #12
    Registered User Array bacchus40's Avatar
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    Quote Originally Posted by ssblade View Post
    In all honesty, I've never felt that the rear brakes on a sport bike gave great feedback at all. It's also a lot harder to modulate the pedal vs a lever..
    yeah i often have the same issue on the R1 and thats with aftermarket rotor n' CL pads, i'm gonna bleed the system this week n' put some proper Motul brake fluid in there to try n' wake 'em up... its annoying
    http://bcusedoil.com/

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  14. #13
    Registered User Array Mechannibalism's Avatar
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    Change to a larger master cylinder, I went from a 12mm to a 13mm and got better feel (it will make the pedal slighty harder)
    You're just a crackpot till you hit the jackpot - Wernher von Braun

  15. #14
    Registered User Array bandito's Avatar
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    Quote Originally Posted by Mechannibalism View Post
    Change to a larger master cylinder, I went from a 12mm to a 13mm and got better feel (it will make the pedal slighty harder)
    I think he'd be best to get the brakes that came with the bike working properly first, before deciding that the mc needs to be changed. That bike has good brakes on it, it's not necessary imho.
    Long Live Shervin Of The North!

  16. #15
    Registered User Array bandito's Avatar
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    So after all this good advice he's asking the exact same question today on 600rr.net

    How many people do you need to ask before you start taking it apart to fix it?
    Long Live Shervin Of The North!

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