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  1. #1
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    Polyurethane bushings installed!

    Here are my thoughts on the installation of Powerflex bushings in the thrust/upper control arms of my '00 540i.

    I opted to simply replace the failing control arm bushings since the rest of the front end is tight and has many new parts already in it. To remove just the thrust/upper arms takes a bit of work. First, you will have to unbolt the swaybar body mounts to clear the control arm bushing bolts. These bolts don't actually come all the way out, as the "drag link" or steering assembly is in the way. The steering actually has to be swung back and forth to access these bolts, remove them far enough to let the control arm drop free.

    The next trick is to separate the balljoint. The good news is the balljoint on the thrust/upper arm is much shorter than the lower arm and the Harbor Freight http://www.harborfreight.com/3-4-quarter-inch-forged-ball-point-joint-separator-99849.html tool works just fine as is, but the fit is tight. I left the lower arm installed for the job. To access the control arm balljoint nut, the strut/shock must be raised up a bit. This is pretty easy to do, just release the pinch bolt and pry down. Getting the arm out was not that tough, swinging a wrench inside all the other components is the tedious part.

    Once the thrust/upper arm is removed most people will tell you the bushing needs to be pressed out. Not so. I used a large C-clamp and a very large socket to press out the rubber center of the bushing. This leaves the bushing sleeve in the arm. Its actually a double sleeve. I then clamped the arm to the bench and carefully used a hacksaw to cut through both sleeves in two places. The cut sleeves tap out easily. The key to doing this is being very careful and patient with your sawing technique. You DO NOT want to cut into the inner diameter of the control arm! I very slightly contacted the inner wall on mine, both of them, maybe 1/64" or less, certainly not enough to have any effect on the strength of the arm.

    So now the bushing is out, what next? Well, if you were using OEM bushings you would need to have access to a press or pay to have it done. The minor advantage to the Powerflex is they install without a press. So I popped them in, greased them up, etc. While the arm was on the bench I also pinched the balljoint grease seal, slid a grease needle inside and put a couple of shots of grease into them as well. Can't hurt.

    Reinstallation is pretty straightforward. I had little trouble getting the Powerflex bushings in. The key was to install one washer, hang it on the bolt, slide the arm in, retract bolt, push arm up and "hang" it all on the bolt. The last washer slides in, tap up into position with a hammer and then slide bolt through. Fiddly but not bad.

    The annoying part is getting the balljoint nut tighted back up. There is a thick washer under the balljoint nut, then the nut, and it is pretty much guaranteed that the tapered stud will turn when you try and tighten the nut. The top of the stud has a 6mm hex on it to hold it while you tighten. Problem is that an Allen key is a bit too tall to fit under the already raised strut/shock. The solution is to take a Dremel and cut down a 6mm key so it fits nicely. If you are smarter than me you clean out the 6mm hex BEFORE you install the arm.... The key fits way better that way.

    Thoughts on the Powerflex? I like them. 95% of the vibration, shimmy, etc. is now entirely GONE. There is a very slight vibration around 75-80mph but the tires are crap and need balancing. I noticed no increase in NVH. The steering is MUCH crisper and immediate. We will see how well they last.

    I'm not married to the idea of polyurethane bushings. This was an experiment to see what would happen and the price was right. Could also do it at home without needing a press. I figure if they last until the balljoints wear out then I may go back to OEM with the new arms. Time will tell.

    Lastly, I have my own thoughts on alignments. I'm not bothering this time around. Why? I am making the assumption that the alignment was originally done with "good" components. Restoring the suspension to its designed geometry should make realignment unnecessary. As long as you are not messing with tierods, drag links, idler arms, etc. the alignment should not be an issue. Obviously keeping a very close eye on tire wear and paying attention to how the car drives is key as well. So far, 130miles today on Powerflex gets a huge thumbs up!

    Enjoy, RT


  2. #2
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    Member No: 21320 edjack will become famous soon enough edjack's Avatar
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    Hope you don't go nuts listening to the >>

    squeaky bushings.
    Ed in San Jose. BMW CCA member since 1987 (Nr. 62319). Golden Gate Chapter. '97 540i 6 speed. Build Date 3/97. Aspensilber over Aubergine leather.

  3. #3
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    Re: Hope you don't go nuts listening to the >>

    I'm pretty sure that's pre updated powerflex bushings that squeek. I remember you told me that when i installed them but its been over a year now and no squeeks

    My windshield did crack possibly from the bushings and bilstien sports. Same exact crack e30 M3's got when they had stiff suspensions (jstock etc). The vibrations and body flex that come with a stiff suspension also cracks windshields that are bonded to the cars structure.

    Andreas
    Queens NY
    BMWCCA# 186796
    86 325es (wrecked by careless driver)
    87 325 (project for life)
    00 540is 6spd (daily driver)

  4. #4
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    Re: Hope you don't go nuts listening to the >>

    I'm well aware of the supposed squeeking issue. The bushings were liberally lubricated when installed. Time will tell. Regarding the windshield cracking I am skeptical about this. The shocks, springs and everything else in the suspension is stock. Why would a bushing that is actually now properly locating a suspension component cause anymore undue stress to the structure of the car than the stock setup? Did BMW build the E39's torsional rigidity so close to the margins that simply removing the VERY MINOR slop a stock bushing allows is going to crack windshields? Seems a spurious argument to me.

    It is understandable that lowered/modified suspensions could cause windshield cracking. Increased spring rates and reduced suspension travel will have an adverse affect on the vehicle structure simply because the suspension will allow more energy to transfer, and more importantly, in short, sharp time periods, to the structure.

    There is very little if any difference in NVH with the Powerflex. Yes the steering has a much more direct feel to it, however the essential character of the suspension is unchanged. Stock shocks and springs.

    This is an experiment. If the results are objectionable I will change back to OEM. I will also post about it for all to see.

    RT

  5. #5
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    u misunderstood me

    the vibrations from the solid bushings ALONG WITH bilstien sports on NYC streets cracked my windshield. i doubt anybody else had this issue with on powerflex bushings alone.

    BTW NYC highways are really bad lately, u can be cruising at 80mph and suddenly without any warnings the next few miles of road has been stripped down for new asphalt. The whole e39 vibrates so bad its tearing itself apart.

    Either way NO SQUEEKS YET lolol

    Andreas
    Queens NY
    BMWCCA# 186796
    86 325es (wrecked by careless driver)
    87 325 (project for life)
    00 540is 6spd (daily driver)

  6. #6
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    Re: u misunderstood me

    I see your point, just clarifying mine. I've been to NYC enough to know that a stock E39 could crack a windshield with the conditions of the roads. RT

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