Just another FINAL DRIVE nightmare....with a twist

Discussion in 'GS Boxers' started by Englishmatt, Jul 29, 2011.

  1. scooteraug02

    scooteraug02 Dog Rancher

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    When you do the 6 and 12 and 3 and 9 wiggle check do it from this side. You can see it move in the middle.

    [​IMG]
  2. def

    def Ginger th wonder dog

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    Here in Dixie, that's normal weight for a husband/wife. Many pickup trucks go down the road lopsided when only one is in the truck...when the passenger is aboard, all is well but fuel consumption increases.

    We love our hog fat and grits here in Dixie...sometimes, we even cook it.:lol3
  3. def

    def Ginger th wonder dog

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    I would think that the GVWR is more related to allowable maximum tire loading rather than bearing load requirements. Have you seen the size of the bearings in the FD? Well, I have not seen the bearings first hand but, in my FD (the one without the hole), the crown wheel bearing is rather large although it is a grooved ball bearing design. Also, the bearing opposite the grooved ball crown wheel bearing is a smaller taper roller bearing (which rarely fails even when the crown wheel bearing fails). I cannot bring myself to believe that these bearings are unable to support the load of the motorcycle and fat rider/passenger (as Anorak so correctly points out) without early failure.

    IMO, the failures are related to the loads applied from the side rather than static load. Also, inasmuch as the taper roller bearing in the older FDs rarely fails, incorporating this bearing style would provide longer service, improved side loading tolerance and allow for rather simple preloading as well as a more tolerant preload range.

    And as Anton says, if it can be assembled by mortals, it can be repaired by mortals. (Anton, you are a mortal, are you not)?
  4. scooteraug02

    scooteraug02 Dog Rancher

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    Final Drive Bearing Replacement ('07 R1200GSA)


  5. rutard

    rutard Magnanimous Madcap

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    You inspired me to make this:
    [​IMG]
  6. FlyingFinn

    FlyingFinn Long timer

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    I have a 2005 GS with a "2010 FD" on it.
    While the above statement is generally true, I have bit of an update on this.

    I'll type more later, but for now I just wanted to resurrect the relevant thread.

    --
    Mikko
  7. FlyingFinn

    FlyingFinn Long timer

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    Like it's been discussed before, the the pre-08 FD units aren't interchangeable with later ones. The reason is the rear wheel speed sensor in the FD. Mechanically the final drives are 100% interchangeable.

    The newer FD units have several improvements over the earlier ones:
    - Larger, more robust pinion bearing
    - Added vent to equalize the pressure, should help the seals
    - New units also come with the steel wheel flange (the aluminum ones are prone to crack)
    And a newer used one is simply likely to have less miles on it.

    But problem is that BMW also changed the wheel speed sensor and the ring gear the sensor reads. To use a 08+ FD in a older bike, there are two fundamental problems that need to resolved.

    1) The sensors are mechanically different size so it's not possible to simply use the old sensor in the new FD.
    2) The sensors use different output signal level. The computer on an older bike can't even tell the rear wheel is turning based on the signal from a new sensor.
    3) The ring gear in the 08+ FD has 48 slots and the older one has 78. Even if the sensor signal levels were compatible, the new FD would make the speedometer read 38.5% too low, and on a ABS equipped bike the ABS computer would throw an error.

    The wheel speed sensors used in the r1200 bikes are 2-wire Hall effect sensors with binary current output. The two current levels of the older sensor are 4mA and 10mA, the new sensor uses 7mA and 14mA.
    That's bad news since all the electronic speedometer calibration devices out there support only other types of wheel speed sensors. Either open-drain outputs or old inductive sensors that produced an AC voltage that was relative to the wheel speed.
    All Japanese bikes, most other European ones and most cars use open-drain output sensors (also called "ground switching" sensors).
    So none of the SpeedoHealer or other comparable products work with our bikes.
    If they did, it would be trivial to plug in one of those, dial in the correction factor and be done with it.

    What I've done is first studied these sensors to figure out the interfaces they use and designed an electric circuit that a) converts the current signal from the sensor to a format that a "SpeedoHealer" can use as its input, and b) takes the open-drain output of the "SpeedoHealer" and converts that back to current signal that is compatible with the BMW computer input.

    I have all the measurement data from old and new type of sensors, how they interact with the computer and simulation results (used a SPICE simulator) of the signal conversion circuits.

    Next step will be to order some samples, build prototypes of those circuits and plug it in with a standard SpeedoHealer. This will take bit of time but I'm quite confident it will work. I have all e data I need, the simulation uses real component models and results are good.

    Mikko
  8. Emoto

    Emoto Sure, why not?

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    :lol3

    Mind if I borrow that?
  9. rutard

    rutard Magnanimous Madcap

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    Borrow away...just make sure to give it back. :huh
  10. FlyingFinn

    FlyingFinn Long timer

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    Got the parts and put together the first prototype.
    Works as expected. So at this point the speed sensor in the FD from 2008+ Bike drives the computer of an <2008 bike.
    The signals are now compatible but speedo is still off.
    Next I'll hook up more stuff into the circuit to make speedo read correct.

    [​IMG]

    [​IMG]


    Mikko