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Front shimmy diagnosis q's

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    #1

    Front shimmy diagnosis q's

    I have some questions about diagnosing and isolating a front end shimmy. Here is my situation. I have a steering wheel shake (back and forth) at highway speeds. All front end components are new except for the rack (used Z3) and control arms. All tires were balanced three days ago. Alignment is perfect.

    The car did not have a shimmy before I began the S52 swap. The control arms are original to the car as I bought it. the only non-standard parts I've installed are the E36 rack and Treehouse eyeballs.

    With the car up on stands, I can get a little movement in the wheels when I grasp them at 3:00 and 9:00, but no more than a 1/8 of an inch. The steering wheel moves slightly with the wheels when I push on them. That is to say that the steering wheel and front tires move together. This indicates to me that there does not seem to be any slop in the rack. Is this a correct assumption?

    Do I need to compress the coil springs in order to help determine if I have worn ball joints in the control arms? I looked them over pretty well before installed them. There wasn't any play in the ball joint studs. I do not know how old the control arms are. They were in very good shape but the studs did not offer a lot of resistance to movement (like a very stiff joystick).

    There is no movement in the front wheels when grasped at 12:00 and 6:00. I'm pretty sure my bearings are OK.

    Any comments and help or tips on diagnosing or isolating would be appreciated.

    Thanks.
    Tags: None
    #2
    Wheel ?

    Do you have original BMW wheels or are they aftermarket?

    If the wheels are not hubcentic do you have the proper rings to center them to the hub?

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      #3
      +1

      That'd be my first thought based on what you've said.

      Sarcasm is a body's natural defense against stupid.
      When a man talks dirty to a woman, it's sexual harassment. When a woman talks dirty to a man, it's £3.95 per minute.
      "My mother never saw the irony in calling me a son-of-a-bitch." Jack Nicholson"
      Old age and treachery will always overcome youth and skill.

      Comment

        #4
        This sounds like an out of balance/out of round problem with the tires, perhaps aggravated by worn control arms or worn shocks. The best way to check the control arm ball joints is to squeeze the joint with a very large pair of channel locks (with the wheels in the air). Any motion in the joint is cause for replacement.

        I'd suggest having the tires re-balanced. Note that if you have non-OE wheels that aren't a close sliding fit to the hubcentric ring it may not be possible to successfully balance the wheels off the car.
        The car makes it possible, but the driver makes it happen.
        Jim Levie, Huntsville, AL

        Comment

          #5
          Yeah, it dawned on me last night that I've changed wheels since I bought the car. Pulled the front tire, took some measurements, and ordered some hubcentric rings today after work. That is definitely my problem.

          I always tend to assume the worst of a situation.

          Thanks

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