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Thread: What Are the Implications of Driving With Failing UCA Bushing?

  1. #1
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    What Are the Implications of Driving With Failing UCA Bushing?

    I get the 55 MPH shaking. Its not horrendous but I am planning at the moment to have Powerflex poly's put into the arms Friday. What am I doing to the tires, the UCA ball joints or other suspension parts if I drive it extensively in this condition? Wearing out the tires? Should I expect I'll actually find the ball joints weakened when removing these arms? Maybe I should order a new pair.

  2. #2
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    Increased wear on components, steering assembly, suspension, strut assembly/housing but realistically unlikely to have any critical failures in a short period of time.

    I like the moosehead spherical UCAB, increased NVH but nothing out of line for a sport sedan . . . they are not expensive at all

    Id do ball joints

  3. #3
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    Minute tire wear. Nothing detrimental Id say. Apparently you’re better off replacing arms completely. I went that route to avoid bushing pressing. If you want poly thats a different story.

  4. #4
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    I ruined a set of snow tires in one season with bad control arms. It can be worse than you think. I went through like 7/16 of tread really fast.

  5. #5
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    I will not use poly bushes, I replaced the old parts with original, OEM parts and all works fine, here some comments on poly bushes https://www.zroadster.net/forum/viewtopic.php?t=42721

    excerpt:
    Poly bushes MUST be periodically lubricated in rotating applications or rapid wear and increased friction will be the result. Prodrive for one do not like Poly bushes as an unlubricated poly bush has higher friction than a rubber bush. For flexing bushes, Rubber has its own inbuilt version of damping, poly urethane does not have this. (well it does but it's different and a complex subject). Urethane also comes in several grades of hardness and not all poly bushes are equal. Most polybushes are 90a which is way too hard for the application. Poly has applications but they are limited. What they are is cheap to make aftermarket and easy to fit, that's the main reason they are everywhere in the aftermarket
    Shogun tricks and tips for the E32 series are HERE!

  6. #6
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    This is interesting... The bushings I have from Powerflex are not the same as I had from them about seven years ago which were Black but two piece. These are one piece and also Black but extremely hard with virtually no yield at all. I was going to return them to Bavarian Autosport which were local to me but they went out of business last week and I am sort of stuck with them ($90).. I suppose I ought to just grab the recommended 750i stock types and use them with the Meyle HD arms I have on order.

    Thanks for speaking up. I never found any noise or harshness issues with the older type and drove them till the rear differential literally dropped out from rust and they seemed to be fine although I have to admit I may have had other problems I never connected with those bushings.
    Quote Originally Posted by shogun View Post
    I will not use poly bushes, I replaced the old parts with original, OEM parts and all works fine, here some comments on poly bushes https://www.zroadster.net/forum/viewtopic.php?t=42721

    excerpt:
    Poly bushes MUST be periodically lubricated in rotating applications or rapid wear and increased friction will be the result. Prodrive for one do not like Poly bushes as an unlubricated poly bush has higher friction than a rubber bush. For flexing bushes, Rubber has its own inbuilt version of damping, poly urethane does not have this. (well it does but it's different and a complex subject). Urethane also comes in several grades of hardness and not all poly bushes are equal. Most polybushes are 90a which is way too hard for the application. Poly has applications but they are limited. What they are is cheap to make aftermarket and easy to fit, that's the main reason they are everywhere in the aftermarket
    Last edited by jehu; 03-14-2019 at 09:45 PM.

  7. #7
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    The biggest thing is the shimmy... especially a bad one, can trash a steering box pretty quickly.


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  8. #8
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    I had bad upper control arms last year ( I have a post on it). Had the shakes over 55mph. By the time I replaced them, my tires were shot. They looked as if I had massive camber and the tires were running on wire. I would replace the tires due to uneven wear.
    At the very least, buy used tires until you can get an alignment and new tires.

  9. #9
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    I am passing up on driving it until I can get them replaced.. have some arms and 750i bushings and if I can't get them installed today I have an appointment for Tuesday morning. Running a set of Michelin Ice X 3 winter tires on the 15" new this Winter so trashing them or the steering box is definitely nothing I need to do.

  10. #10
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    Quote Originally Posted by jehu View Post
    I am passing up on driving it until I can get them replaced.. have some arms and 750i bushings and if I can't get them installed today I have an appointment for Tuesday morning. Running a set of Michelin Ice X 3 winter tires on the 15" new this Winter so trashing them or the steering box is definitely nothing I need to do.
    I installed the OEM 750 bushings on one of my e32 740's and they worked great. They are now starting to wear out after about 55,000 miles. Somewhere on the forums somebody posted insight into the stiffness of all the OEM BMW options and the part numbers (from the e34, e32 and e31 models). I can't remember what was the most durable but I believe the top of the list was either e34 M5 or e32 750, then the e34 740, then the rest in some order...

    I want to try spherical bearing type bushings (there are a couple different aftermarket options out there) but I fear that they would be too harsh on expansion joints and other imperfections of the road. I did install the e31 lower control arms which have spherical bearings in stock form and there was no increased NVH, but they don't see fore and aft loads like the thrust arms, only lateral loads. The e31 lower arms did make the immediate turn-in response slightly better which was nice.
    Last edited by m60power; 03-15-2019 at 07:40 PM.

  11. #11
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    More folks just need to drive cars with Moosehead bearings. Since they made those things serviceable, they are an awesome lifetime-of-the-car upgrade, with negligible trade-off. I love them even more paired the the E31 lower bearings.
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    Quote Originally Posted by danespann View Post
    Every E34 needs the same things in the end.

  12. #12
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    To Update this I had the new Myle HD arms and 750i bushings installed today and when I got onto the highway over 65 the shaking was terrible ... I assumed it was the tires so went straight to have them rotated front to rear which substantially corrected the matter so Its pretty clear driving with busted UCA bushings will croak your tires even though they measured even per the tire shop. Interestingly the ball joints were fine and I probably didn't need the arms... anyone need a pair of UCA's?

  13. #13
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    moroza is offline MORΩN ΛABIA BMW CCA Member
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    Quote Originally Posted by m60power View Post
    Somewhere on the forums somebody posted insight into the stiffness of all the OEM BMW options and the part numbers (from the e34, e32 and e31 models). I can't remember what was the most durable but I believe the top of the list was either e34 M5 or e32 750, then the e34 740, then the rest in some order...
    Yup.

    When I refreshed my 525i suspension a few months ago, I made sure to get the correct (blue) bushings. The pair of thrust arms I bought came with one white and one green (750iL) bushing.

    I'll also add my experience of replacing stock 534i bushings (white) with 750iL: I noticed a stiffer ride and a lighter wallet, and nothing else.

    Quote Originally Posted by BleedsBlue View Post
    More folks just need to drive cars with Moosehead bearings. Since they made those things serviceable, they are an awesome lifetime-of-the-car upgrade, with negligible trade-off. I love them even more paired the the E31 lower bearings.
    I have a hard time believing that reducing the fore-aft compliance in the suspension that much would be negligible. Now, if somebody made a greasable spherical bearing encased in the same rubber as the OE bushing, I'd spring for that.
    Last edited by moroza; 03-19-2019 at 11:16 PM.

  14. #14
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    Quote Originally Posted by moroza View Post
    Yup.

    When I refreshed my 525i suspension a few months ago, I made sure to get the correct (blue) bushings. The pair of thrust arms I bought came with one white and one green (750iL) bushing.

    I'll also add my experience of replacing stock 534i bushings (white) with 750iL: I noticed a stiffer ride and a lighter wallet, and nothing else.

    I chose the 750i bushings primarily for the hope they simply last longer . There was I heard a service bulletin for the 540 to do this. While the rest of the 5 series could use the e34 part the 540's were busting them sooner.

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