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Shimmy

Discussion in 'Wheels & Tires' started by Jaeger, Jul 30, 2009.

    Jaeger guest

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    When I bought my 7 from the previous owner, he informed me that because of the wear patterns on the tires I would get some shimmy. However, having been told that it could be warped rotors causing my trouble, is there any gauge of surety other than replacing both?

    (Shimmy: The steering vibrations occurring during braking. If I brake harder, it goes away.)
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    granthr

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    I am not positive, but that sounds like it could also be worn control arm bushings. I say this because it goes away if you brake hard.

    Jaeger guest

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    Sounds like another potential. How easy are said control-arm bushings to replace?
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    granthr

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    Not sure about an E38 (7 series 95-01), but if they are like most BMWs it is not too difficult. The tough part is that you really need a hydraulic press to get the bushing into the "lollypop" (the metal bracket that holds the bushing). So if you are going to try this yourself you could just take the bushing and lollypop to a shop to have them press it in. The other issue is getting it onto the A arm. Bavarian Autosport sells a tool to do that. It isn't cheap, but one use and it pays for it's self. The thing is this isn't the type of job you will do very often. Check with your local chapter, someone might have this tool for you to borrow. If you are going to do this yourself, buy the Bentley Repair manual. http://www.bentleypublishers.com/isbn/9780837615318/index.html

    The other option will be of course to pay a pro. If you don't have a mechanic I highly suggest you find an independent BMW mechanic that you trust. You can find one here, http://www.bimrs.org/

    Jaeger guest

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    Sounds fun. Due to cost and budget, of course, I'll be doing it myself. Fortunately my car came with the Bentley manual, as the previous owner was very serious about taking care of it, so that's $140 off my initial cost! Thanks for the forecast of what fun I may encounter. This is what dads are for -- helping replace those difficult parts. :D
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    granthr

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    Yes dad's are good for this sort of help, as long as they are mechanically minded. Sounds like you have a good project a head of you. But before you start make it is in fact the bushings that are bad. I think the bentley gives direction on tell.

    I just looked up your suspension on www.realoem.com. A very valuable tool. Here it is http://www.realoem.com/bmw/showparts.do?model=GJ83&mospid=47531&btnr=31_0248&hg=31&fg=05

    You have a different set up then my E30s and E36. I am guessing here, but if item 5, 6, or 10 on the above diagram are worn out, it could be the cause of your vibration. You can probably still do this yourself if you have good tools and mechanical knowledge. The tough part will be if things don't want to come apart. Bavarian Autosport also sells a tool to coax the ball joint stud out of the suspension strut. It will make life easier for you.

    Good luck.
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    CRKrieger

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    OK; as Grant just learned, the big cars don't have A arms. The most likely culprit is the bushing at the big end of Part #10. It can be a bit of a PITA to get the bushing pressed out and replaced, but this is the time to check the ball joint at the other end. If it moves freely, then it is nearly worn out as well - and it is not separately replaceable. You'll probably find the whole arm with new ball joint and bushing installed to be a very reasonable alternative since it is a simple unbolt and replace operation. At least, I do on the E28 that has basically the same arm and bushing. In fact, one of the best replacements for the E28 bushing is the E32 750 bushing - milled slightly narrower to fit - in the E28 control arm.

    Once you have replaced these (do both sides at once), you may find your problem gone. If not, you have prevented it for the next ~150K miles - because they will wear out eventually no matter what else happens.

    Jaeger guest

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    In essence, you're suggesting I check and see if the ball joints need replacing; and if they do, simply purchase the whole assembly instead as preventive (or corrective) maintenance as it's simpler and more cost-effective?
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    CRKrieger

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    Correct. I figure that, by the time you've gone to the trouble of pressing out and pressing in a bushing, you're left with a labor bill and costs that nearly equal the whole part (costs ~$130-$175 for an E28) - and you still have a used ball joint at the other end with who-knows-how-many miles left on it. When it finally gets bad, it can destroy the bushing and other ball joints as well. If you have your own press, or free use of one, it might be cost effective. Otherwise, the smart money is on buying a new arm.

    Jaeger guest

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    Considering that it's nigh $100 for the pair of bushings, I would likely better off with the full setup. Now I just have to see if it's worn out under there... Thanks for the advice there, CR.

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