new 12GS, rear brake rotor hot, front not...

Discussion in 'GS Boxers' started by PaulC, Apr 19, 2006.

  1. PaulC

    PaulC Adventurer

    Joined:
    Mar 11, 2006
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    20
    Hello:
    I have 220 miles on a new 1200gs. Returning from a short ride, I parked the bike in the garage. I happened to look at the rear rotor, and it has distinctly different color than the front - it is a little reddish, more like copper. I touch it, and it was quite hot - I could only hold my fingers there maybe a half a sec or so. The front is cool to cold.

    I use both front brake lever and the rear brake pedal when stopping.

    I will watch it some more tomorrow. Too bad with the linked brakes I cannot make a test of riding, stopping only with the front, and seeing what is happening with the rear rotor. I guess I can try to stop with the engine only, rolling into a stop But in the meantime, does anyone have any ideas what could be causing it ? Or anyone having similar problem ?


    Thanks, Paul.
    #1
  2. sick'ntired

    sick'ntired Banned

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    Surely you're not being "big foot" near the rear brake lever. 1st thing to watch. Some times new boots will migrate toward there.
    #2
  3. retroone

    retroone Long timer

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    Look around the rotor holes and see if there are funny marks/hard spots. If so I thing you have the dredded brembo shit rotor. If under warranty tell them you can feel grindy rear brakes and pulsation. They should replace it.
    #3
  4. PaulC

    PaulC Adventurer

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    I sure hope not, but I will watch for it. Another reason I am hoping this is not the case is that it seems there is quite a bit of travel on the rear brake pedal before it acts, seems longer than my old 1150gs.

    PaulC
    #4
  5. JimVonBaden

    JimVonBaden "Cool" Aid!

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    Coming from an R1100GS I felt the same way. I still think so. Still, as many have said, they all do that, so no worries!

    Jim :brow
    #5
  6. DeSoto

    DeSoto Been here awhile

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    My rear is not discolored, but I was dragging the rear brake when I first got my R1200GS. The only tip I got was because I rode it at night. I have installed one of those LED flashing modules. I noticed I was applying the brakes because I could see the bright lights in the mirror. At first I thought something with the switches was wrong. I kept looking in the mirror and finally put two and two together. Now that I have ridden it a little more, I have no problem with my foot positioning.

    You might try going for a ride and try to keep the balls of your foot on the peg. This will keep you from catching the pedal with the boot. Then check the rotor temp. I would have sworn I wasn't touching the rear brake pedal. I don't know what other bikes you have, but I also ride a HD Ultra. I think because of the vastly different locations of foot positions, this was contributing to the problem. I also switched to the fastway foot pegs. That might have helped too.
    #6
  7. drdata

    drdata R1200GS

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    Mine are the same. I generally add no rear due to linking.

    Make sure the wheel spins freely and you should be OK.
    #7
  8. SamTheEagle

    SamTheEagle Sam the Eagle

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    Mine, too.

    Keep your eyes on rear brake pad wear.

    Since getting the R12GS I have had to adjust to NOT using any rear brake if at all possible. Heck, I'm even trying to use more engine breaking as a general rule of thumb. Because the brakes are linked, there's not much point in using the rear brake lever, unless you want rear-brakes-only.

    Even after consciously not using rear brake, my rear rotor still gets quite hot.
    My first set of rear brake pads wore out in less than 6000 miles! :puke1


    - Sam
    #8
  9. PaulC

    PaulC Adventurer

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    Thanks for the info.

    I did some checking - I put the bike on center stand, with front wheel planted on the ground the rear is up in the air. Started the bike, shifted to neutral:
    - the rear wheel spins, slowly, and any small resistance by hand will stop it.
    - when operating the brake pedal, at some angle, I first hear the servo mechanism working, then as I pressed the pedal more, the wheel stops - the pedal is depressed quite a bit low, plus there is definite resistance coming back from the pedal - I am 99% sure my boot would not cause that.
    - when the pedal is released, the wheel will start spinning again
    - the front lever is much more sensitive - a light touch stops the spinning or the rear wheel.

    This is what the service manager says;
    - rear wheel spinning while in neutral is normal. IS IT ?
    - there is no spring pushing the brake pads back, so there is always some contact between the pads and the rotor. I am not supposed to touch the rotors after a ride, they will always be hot. When I asked why is the front not hot, he said that there is the 2 rotors front vs. 1 iin the back, smaller pads in the back, and the linking puts more braking power into the back.

    What bother me is that my test showed almost no resistance from the pads on the rotor, even after I operate the brakes several times - that would contradict the explanation from the service manager. So there must be some intermittent change, or it is different when I am riding, vs. the stationary test.

    I have to admit this issue is bothering me. I do not want to be replacing pads after 6K.....

    PaulC
    #9
  10. drdata

    drdata R1200GS

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    Get sintered pads for the rear, as I got from BMW dealer at 9K when I replaced the rear pads, which were organic from the factory. Rear caliper seems a lot cooler now, but this could be because I do not add rear anymore. I tend to believe what the service guy said. The rear is a semi-floating design, which is why one pad is thicker than the other; the rear pads do seem to drag more than front.

    Click the link below called "wisdom' and check out the write up on rear brake pads for dummies. I followed this when I replaced my pads. A informative/funny write up, easy to do, and adding some lube to make extra sure that the caliper is floating freely on the guide pin would provide peace of mind.

    Regards

    PS> Many postings here about rear pads getting eaten for lunch. I personally feel its because of organic fitting at factory. Some claim its too much bias with the linking.
    #10
  11. SamTheEagle

    SamTheEagle Sam the Eagle

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    Yes. I've seen plenty of people here report that their rear wheal spins while in neutral (and on the center stand). And this happens on mine too.

    Regarding the 6K ... I should have mentioned that I do mostly city driving and I'm slowly realizing just how much worse this is for brake wear. I use my brakes every couple seconds, compared to highway driving where you might not use your brakes for many minutes at a time. My 6K is by far on the exteme of the low end.

    I can't help but say that I think that the rear brakes shouldn't be hot to the touch the ways these brakes are.
    #11
  12. PaulC

    PaulC Adventurer

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    I think I figured out what is going on....
    - good news - brakes do not get hot just by riding, so no friction while riding
    - bad news ( IMO ) - the front-rear brake linking puts almost no braking action into the front

    I rode on open roads for many miles, used engine braking only, then stopped in an uphill stretch without brakes - rotors were just pleasantly warm to the touch.
    Then I did a test, where I did some fairly hard braking, using the front lever only - result was rear rotor VERY hot, even quick touch would be painful, front rotors warm, but not hot, very easy to hold. To me this means that the front brakes are not really active, and the braking is all done in the rear brake.

    I would appreciate hearing how this works on other 1200gs, I am a little surprised with this finding....

    PaulC
    #12
  13. spanner.rash

    spanner.rash musn't grumble

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    Quote:
    - bad news ( IMO ) - the front-rear brake linking puts almost no braking action into the front

    PaulC[/quote]

    Paul,

    The rear pads are in contact with the rotor all the time, and are squeezed when either front or rear braking occurs. The fronts are floating, not in as close contact with the front rotors as the rear. Please be assured that 60 per cent plus of the braking force is applied to the front with the linking system. The larger diameter front rotors dissipate heat quicker than the rear, and are "in the breeze" more as well.

    FYI I've had one front rotor replaced under warranty at 1500 miles, and the rear rotor at 3,000 miles.
    I mostly ride in town, and use the back brake for nipping through lanes of stationary traffic , as well as hill starts. I concur with you that there is loads of pedal travel before anything happens. IMO Its rubbish about riding with your boot on the pedal.I have size UK 12 MX boots and had to buy a pedal extender to actually get my boot onto the pedal!
    #13
  14. PaulC

    PaulC Adventurer

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    Thanks for the reply.

    my tests seem to show the opposite - no signifficant heat buildup while riding, so if there is contact of the pad with the rotors, it must be very light.

    I, of course, do not have a test bed to test the brake action distribution between the front and the back, but if I get up to 50 mph, slow down pretty rapidly, check the rotors immediately - so that they cannot cool down - and the rear is very hot, and the fronts are just warm, I have to assume the braking is dominant in the back.

    If you have a 1200gs, could you, please, try these 2 tests ? Riding, stopping without braking, checking the rotors. Then a stop with the front lever only, and immediately checking the rotors.

    PaulC
    #14
  15. drdata

    drdata R1200GS

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    Well, I use front only most of the time, and the last I checked my rear rotor is was warm, warmer than the front, but not hot.

    If you try an experiment with rear only, and try and emergency stop, you will fine it breaks loose pretty easy. Now try again with only front. If it was really putting all the bias into the rear the two will seem similar. I bet the front only stops you significantly faster.
    #15
  16. Ken H.

    Ken H. Been here awhile

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    Doesn't sound right to me. With the front lever only, despite the linking you should be getting significant front braking. I'd have the dealer re-check the ABS unit if it was me.
    #16