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Thread: Pulsating....

  1. #1

    Pulsating....

    ....in front brake especially under 10 MPH. I assume this means I need a new rotor. Could this be caused by anything else besides warped rotor?

    Thanks, Terry

  2. #2
    Liaison 20774's Avatar
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    Singe ATE disk, R75/7 right? One of the threads in the Similar Threads pane below is in the Airheads section of the forum. Have a look there from some member thoughts.
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    '78 R100/7 & '69 R69S & '52 R25/2
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  3. #3
    If you are getting pulsating in the hand lever, they you should just get a new rotor although it's worth checking your wheel bearings also. But if you are just getting a pulsating braking effect, and the lever itself doesn't pulsate, then you may be able to get away with cleaning the rotor with something like a rotor hone.
    Anton Largiader 72724
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    Virginia Motorrad Werkstatt BMW motorcycle service and repair in central Virginia

  4. #4

    and brake cable...

    Quote Originally Posted by AntonLargiader View Post
    If you are getting pulsating in the hand lever, they you should just get a new rotor although it's worth checking your wheel bearings also. But if you are just getting a pulsating braking effect, and the lever itself doesn't pulsate, then you may be able to get away with cleaning the rotor with something like a rotor hone.
    Yes, it is in the hand brake and is strong pulse there. So new rotor is needed, I guess. Also, brake cable is original (dated 7/76), This should be replaced as well, yes? I will definitely be checking the bearings when I have the wheel off as well. Thanks
    1977 R75/7
    1982 Suzuki GS1100L

  5. #5
    If disc is warped, it could be detected in a machine shop on a granite table.

    If so, it CAN be flattened by grinding as long as one does not have to go below safe level specs to do so.

    BE SURE that the person grinding, is a real machinist and not a neophyte. The disk when set up on first side, MUST be shimmed at the high spots so that the magnet does not pull it down flat. If it does that, it will get ground flat, and then when the magnet is released, it will then go back to its original warped state.

    When shimmed, this prevents the magnet from pulling it down flat - keeping it in its warped state. Then when ground flat on the first side, it can then be flipped over to do the second side.

    This also only works on magnetic rotors - if it would be pure Stainless steel, it will not be magnetic.

    ------------
    Also check how the rotor is mounted. I could have the effect of being warped because it was mounted with dirt, etc. under it, causing it not to be flat with the rotation of the wheel.

    If wheel bearings are bad, or have not been adjusted up properly (with the in-between bearing spacer), allowing the wheel to fluctuate side to side, it will also feel like a warped brake rotor.
    "The difference between death and taxes is that death doesn't change every time congress meets." - Will Rogers

  6. #6
    Rally Rat 1074's Avatar
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    Rotor

    Yup. I'd replace the rotor. You can get a better deal by betting a Ferodo or EBC rotor and corresponding pads rather than going OEM. The aftermarket parts work better. If it is a 1970s bike then I'd consider replacing the rubber brake line as well to get the system in top working condition.
    Boxerbruce

  7. #7
    Quote Originally Posted by AntonLargiader View Post
    If you are getting pulsating in the hand lever, they you should just get a new rotor although it's worth checking your wheel bearings also. But if you are just getting a pulsating braking effect, and the lever itself doesn't pulsate, then you may be able to get away with cleaning the rotor with something like a rotor hone.
    On the one hand, before you spend money it's worth cleaning off pad material from the disk with emory cloth. I then use alcohol rather than brake cleaner to get the dust off. On the other, it's an old bike and a new EBC, or other accessory brand, disk and pads may improve braking response.
    '61 Clubman's Gold Star, '13 690 Duke, '13 Daytona 675R, '14 Street Triple R, '17 1290 GT (gone but not forgotten: '76 R75/6, '84 R100, '76 R90S)

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