Alignment issue 1150 GS

Discussion in 'GS Boxers' started by FourG, Jan 14, 2013.

  1. FourG

    FourG Adventurer

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    To be honest, I think I'm just being lazy. I think I will try to do the bearings soon as I'm now planning a 10k ride through Alaska for August... Better be safe than sorry. We'll see if it kills 2 birds with the one bearing.

    Thanks all for your input.
    #41
  2. the_menno

    the_menno Forever Noob

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    My vote is for gyroscopic procession.
    #42
  3. FourG

    FourG Adventurer

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    Due to? New Tires?
    #43
  4. the_menno

    the_menno Forever Noob

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    Due to a rotating crankshaft along a longitudinal plane, is my answer.

    Like member Bemiiten said: 'Heavy crankshaft spinning along the bikes axis causes a torque effect. They all do it'.

    I have to agree.
    #44
  5. roger 04 rt

    roger 04 rt Long timer

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    Weight imbalance side to side, which is the same as rear wheel offset errors as I mentioned earlier.

    The crankshaft rotating along the longitudinal axis only produces a short term force due to changes in angular momentum caused by changes in rpm. Once the engine is steady, no more force.

    Try adding 5lbs. at a time in either side case and see what happens.
    #45
  6. Chat Lunatique

    Chat Lunatique aka El Gato Loco

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    My GS pig runs straight as an arrow both under acel and cruising. Isn't the counter-balace shaft design supposed to compensate for this effect? Wouldn't all Beemers torque steer if this was the root problem?

    Too much brain freeze in the Peg eh? :lol3
    #46
  7. roger 04 rt

    roger 04 rt Long timer

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    As I mentioned the only time there is a torque effect is when you change engine speed, and then only momentarily. Try it yourself. Stopped with the engine running, balanced on your toes, quickly blip the throttle, the bike leans left. Increase the rpm from 1000 to 4000 though, and once at 4000 it takes no more force that at idle to hold the bike upright.

    The root problem is either rear wheel offset which should be designed to counterbalance known weight offsets or side to side weight differences caused by fuel, transmission, exhaust, FD, etc. To convince yourself just start adding 5 lbs. at a time to one side or the other.

    A bent frame could also cause tracking problems but many boxer models have 10-15 lb. side to side imbalances. And they all have some amount of rear wheel offset.
    #47
  8. Chat Lunatique

    Chat Lunatique aka El Gato Loco

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    Nope, it doesn't happen on my ride.
    I am familiar with torque effect on small aircraft where one has to kick on opposite rudder to keep a straight track on takeoff.
    #48
  9. roger 04 rt

    roger 04 rt Long timer

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    Hi, I'm a pilot too. I think this is the effect you're referring to (courtesy of flightgear.org):

    Prop wash
    A propeller pushes air not just horizontally to the back, but more in a twisting helix around the fuselage (clockwise as seen from the cockpit). As the air whirls around the fuselage it pushes against the left side of the vertical tail (assuming it is located above the propeller's axis), causing the plane to yaw to the left. The prop wash effect is at its greatest when the airflow is flowing more around the fuselage than along it, i.e., at high power and low airspeed, which is the situation when starting the takeoff run.

    To my own surprise, I realized that there's a sort-of weight and balance side-to-side calculation affected by rear wheel offset. Then I just went out and rode various weights. Of course the RT has a major fuel imbalance that I believe is not so prominent on the GS.
    #49
  10. TUCKERS

    TUCKERS the famous james

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    Wow! Not one mention of paralever bearings/bushings and he says he has play in the rear wheel.

    Choose either OEM or Rubber Chicken Racing and do your paralever.

    On center stand have someone hold the rear brake down. Rock the wheel now, and if it moves AT ALL you need to do the paralever bushings/bearings.

    If it only rocks with the brake off you need to do your Big final drive bearing.
    #50
  11. Ron from BC

    Ron from BC Long timer

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    Is that not a symptom of worn pivot bearings.....not tracking in line with front wheel?
    #51
  12. tagesk

    tagesk Tuscan rider

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    ....and it the effect of accelerating a rotating mass.

    [TaSK]
    #52
  13. bemiiten

    bemiiten League of Adventures

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    No counterbalance on a 1150.
    #53