GS1100 front brake disc loose

Discussion in 'GS Boxers' started by pacman6009, Sep 19, 2010.

  1. pacman6009

    pacman6009 Adventurer

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    Looking for help in working out why the front wheel, left side brake disc is loose on my R1100GS?

    It has a small amount of play - 0.05 mm - even though the hex bolts securing the disc rotor to the wheel are rock solid tight!

    I was wondering if maybe there were fibre washers or something that have worn away / out?

    Or its meant to have a small amount of play in it?

    Thanks for taking the time to read this query

    Pacman
    #1
  2. mouthfulloflake

    mouthfulloflake Not afraid

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    there are some flex washers or something underneath the mounting bolts I think.

    Ive read ( here) about some folks wrapping thread to take the play out..
    or order shim washer things.

    Mine do the same thing ( 95 r1100gs) it clicks at the beginning of every stop.
    #2
  3. hasenwerk

    hasenwerk Long timer

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    Mine has a small amount of play as well even though the bolts are tight - I guess this allows for a bit of potential warp in everything. I have sampled several others and I think it is the same old "they all do that".
    #3
  4. mouthfulloflake

    mouthfulloflake Not afraid

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  5. pacman6009

    pacman6009 Adventurer

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    Hey Lads,

    many thanks for the info . . .

    I've only just noticed the movement, but it seems to fit what 'hasenwerk' and 'mouthfulloflake' are also experiencing.

    I'll keep monitoring it to see what happens.

    The bike still stops . . . so far anyways!

    Thanks again.

    Pacman
    #5
  6. Lensgrinder

    Lensgrinder Long timer

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    The rotors are supposed to float a little. My 1100GS did the same thing and my 1200GS rotors float as well.
    #6
  7. wrysingfeenix

    wrysingfeenix Dust off those ashes

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    What he said.

    #7
  8. vintagerider

    vintagerider Long timer

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    Measure your disc with a caliper. Compare to minimum allowable thickness stamped on the rotor. It is most likely worn out. The mounting holes in the rotor get worn (obviously from excessive wear). If the rotor thickness is within spec, order the rotor mounts kits from BMW as above noted in the above link. Heat the mount screws with a small pencil torch to melt the thread lock and they come right off. You will see what I mean regarding worn rotor holes when you pull the first screw. When new, the 1100 rotors did not have noticeable play in them , at least not the ones that I have seen. Yes they were floating design but that they should not flop around on the hub. Checking a new old stock R1100RTP front wheel since this at 8:04pm, the rotors are tight and do not move by hand. The RTP and GS used the same rotors and hubs.
    #8
  9. def

    def Ginger th wonder dog

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    Do not attempt to remove the float clearance in your front rotors. The float is there by design.
    #9
  10. Steptoe

    Steptoe steptoe

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    The 1100/1150 and 1200 discs aren't meant to have play. Hence why the original poster has play in only one disc.
    I'm not sure about the later 2008 onwards 1200 disc with the built in mounting bolts.

    If the discs move the wavy washers under the bolts have worn .

    If not replaced, over time the disc mount holes wear oval, and the disc mounts on the wheel also wear uneven.
    #10
  11. Hunsta

    Hunsta Have guns will hunt

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    Dont know about the wave washers, but when I changed my pads recently. The old ones had small wire frames on the top sections of the pad. These were I assumed to stop pad rattle. The new ones had the holes but no wire, so I had to drill out the rivets and rivet them into the new ones.
    #11
  12. supershaft

    supershaft because I can

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    I am not sure I am following everyone. I have never seen the rotor's button holes wear. It had always been the buttons. It has always been the buttons wearing more so than the wavy washers but to what degree I don't know for sure because I always replace the wavy washers when I replace the buttons. Floating rotors often get quite a bit of axial slop in them as the buttons wear. What really needs to be monitored is the radial forwards and rearward slop caused by worn rotor buttons.

    A very popular misconception about floating rotors is that they float to allow for axial side to side play. Not so. They float to allow radial expansion. Radial expansion is what warps rotors kind of like a thin slice of potato heating up and turning into a potato chip.
    #12
  13. Lensgrinder

    Lensgrinder Long timer

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    They do float.

    Check out link.
    http://micapeak.com/bmw/gs/gs_tel1.html

    <TABLE border=1 width="90%" bgColor=#ffffcc><TBODY><TR><TD bgColor=#ffffcc align=left>Front brakes: <TD bgColor=#ffffcc align=left>Twin 12 inch (305mm) floating discs
    Twin four-piston Brembo calipers with angular pad wear compensation
    </TD></TR></TBODY></TABLE>
    #13
  14. vintagerider

    vintagerider Long timer

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    Lensgrinder, Pacman's question was regarding loose rotors. "Floating" simply refers to what Supershaft said, the rotors are allowed to expand to prevent warping. The rider should be able to grip the rotor forcefully and it should NOT move. (1100-1150). As Steptoe mentioned, loose rotors need attention.
    #14
  15. Lensgrinder

    Lensgrinder Long timer

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    Without seeing them in person it is difficult to know if it looseness is radial or axial. I was only stating a fact that there is a little float which is exactly how they are described. I agree with what supershaft said, but what steptoe said could be misunderstood as well

    "If the discs move the wavy washers under the bolts have worn" .

    After replacing bolts and wavy washers the rotors on my 1100 moved(floated) because that is the way it is designed.
    #15
  16. Steptoe

    Steptoe steptoe

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    It is not the way they are designed - otherwise they would have movement from new and every single bike would also have movement.

    The GS discs aren't meant to have any play - RT/ RS and R series do have floating discs, they do have play.

    The GS discs are the same all the way through the model range from 1100 up to 1200 - no play.
    #16
  17. vintagerider

    vintagerider Long timer

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    Looking at a set of low mileage used BMW 1100 RT? GS? rotors, the rotor mount holes are oblong radially to permit expansion (i.e. floating). 1100 GS that I have seen with loose rotors have these holes also egged out, forward and aft of the pin contact area, from wear. It is extremely obvious what is worn once the rotors are dismounted. If you can grip the rotor and twist it in or against the direction of rotation and there is slop so that the rotor can bang against the mount pins when applying the brakes, that is obviously wrong.
    #17
  18. Steptoe

    Steptoe steptoe

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    Sorry, in my old age i meant to post the K series RT RS have floating discs.

    The R series RT and RS do have the same discs as the GS but with a larger radius, i should know i have my own high quality discs manufactered and sell them online in my "gsshop" :D

    For a disc to "float", it has to have two seperate components, a disc and a disc carrier joined together by "bobbins" or "top hats". And they float "across" the caliper and wheel, not backwards and forwards.

    The GS uses a one peice disc, attached directly to the wheel.
    #18
  19. rglohre

    rglohre Adventurer

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    #19
  20. PartTimeTravel

    PartTimeTravel Been here awhile

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    They should move a bit. Even new disks and new wave washers will still move a bit. It is meant to do so.

    With over 400,000km on mine, i replaced the bolts, washers and disks recently. They still move as designed. NOTE the bolts were not worn.

    Btw, use loctite on the bolts and correct torque.
    #20