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Urethane subframe bushings, diff mounts and RTAB's on street driven car?

Discussion in 'E30 (1984-1993)' started by Grinch337, Mar 18, 2009.

    Grinch337 guest

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    I am replacing my suspension and don't know whether urethane subframe bushings, diff mounts and RTAB's are going to be too harsh on a street driven car? The car will also be used for track days and autocrossing. Does anyone have any insight?

    I am between getting all stock vs. getting urethane bushings from AKG Motorsports. Is there anything else I should be looking at?

    Thanks.
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    mooseheadm5

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    They will be harsh, they may squeak, and they will transfer a LOT of driveline noise to the cabin. You will hear the diff through the body.
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    MGarrison

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    Yup, what Paul said - urethane subframe and diff. mount will increase the in-car noise level an order of magnitude. If you're not willing to put up with that, you might want to reconsider.

    What are your overall goals/long-term plans? That should guide your decision process.

    Looking for increased durability of those wear items? Better handling? What?

    There's a bazillion options for these cars depending on what you want to do.

    Daily driver with 1-2 driver's schools a year, 1-2 autocrosses, and you're just beginning driver's schools and the learning curve for that? IF the stock suspension is in good shape as are your street tires, probably best to leave it stock and take care of any needed maintenance items for the pre-event tech-inspection.

    As far as learning goes while maintaining larger safety margins, stock configuration vehicles are generally best for that. I think most would recommend that you do driver's schools basically stock until your skill and comfort level gets to the point that a specific thing becomes a substantially limiting factor.

    For instance if you and your instructor jointly agree that you're now driving the car as best, optimally, and as fast as you can, but now you're exhausting the performance envelope of your street tires, and perhaps choosing a hi-performance or wider tire might be warranted.

    After that, things open up a lot.

    First upgrade that will show a substantial difference: tire upgrade. R-compound tires are, generally speaking, probably a bit much to jump into as you do your first several driver's schools, as you'll learn more about how to manage your tires in less time with a greater safety margin than if you opt for some super-sticky mega-tire early on.

    Next fairly obvious and inexpensive things are stainless steel brake lines and higher performance brake-fluid, such as ATE Super-Blue.

    It starts to get to be a balance of choices - on-track safety vs. say, performance. At which point do you decide a roll-hoop and 5 or 6 point harnesses trump a suspension, handling, or power option?

    If the track bug bites you, and you decide to do enough events that you progress to the advanced class levels (typically, A or B run groups in a 4 run group school), by the time you get to that level, a roll-bar is probably appropriate, despite it's compromising BMW's engineering & design to make the interior as safe as they knew how in case of a wreck or rollover.

    But, if it's 1 or 2 driver's school a year for the forseeable future, maybe you opt to hold off on that path, and start going for handling.

    Common E30 stuff - larger swaybars w/ urethane bushings (yes, the bushings may very well squeak nearly constantly, for years). More negative camber via offset strut mounts, lowering springs (w/ obvious ride-quality compromises), camber plates (or adjustable camber options), and rear trailing arm modifications, or bushing kits.

    Hi performance or sport shocks, front or rear shocktower stress bars, offset control-arm bushings, beefier or reinforced rear shock mounts, and probably lastly consider the substantially stiffer urethane bushings throughout, but of course that consideration will come up as various typical suspension maintenance items come up. And then there's the various things that should be re-inforced or beefed up - motor mounts, swaybar mounting points, etc. And then you have to consider that all those nice, compliant rubber bushings you're replacing with something substantially stiffer won't be absorbing what it was before, and that force and energy has to go someplace, and will be transmitted instead to a steel piece which was never designed for that level of stress and will crack or suffer unless reinforced.

    (had a friend w/ his E30 M3 that had a cracked front subframe; however, its solid control arm bushings didn't have much option for force dispersement; I'll take the rubber M3 ones with their more frequent replacement interval and deflection over the option of a front-subframe failure).

    Of course, given the mileage on E30's these days, hardly anyone's going to go through a linear modification and upgrade path, more likely you need to make some decisions because why duplicate the labor expense for the same work down the road if you think you'd be inclined to do the modification anyway at some future point. If you drive the car all day every day, the stock rear subframe bushings are definitely quieter, and quite long-lived. Urethane bushings might not wear enough to require replacement if you owned the car for the next 20 years (I'm guessing, don't place a bet on that).

    Best of luck regardless what you decide!

    Grinch337 guest

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    Thanks for the replies guys. To give you a little more information:

    I've had the car for a few years, but havent been driving it that much (its been a second car). The car is now going back into daily driver duty for the next one to two years. The car has 151,000 miles on it and is still on the original suspension and bushings. Needless to say, things need to be replaced. Other maintenance items have been taken car of, however I am due for a timing belt change in the fall or next spring.

    While the car is in daily driver duty this year it will see 3-4 autocrosses, as well 1-2 track days. This year will be my first time on a track, but I have been karting for a few years and have done several autocrosses. Tracking cars is going to be a long term hobby of mine. The only reason I am just starting now is because it is only now becoming financially feasible for me. I am also going to continue to drive karts as well.

    In 1-2 years, the car is going to become more of a weekend hero/track car.

    Last year I replaced the motor mounts and the tranny mounts with Ireland Engineering polyurethane. Any initial increase in NVH has subsided, and I really like the increased stiffness. However, it is difficult to compare to stock since my old motor/tranny mounts were pretty tired.

    As far as my replacement list goes (please feel free to give me feedback on this):

    Bilstein Sports
    H&R Sports
    IE Fixed Camber Plates
    Wheel Bearings
    Control Arms (either Lemfoerder or Meyle)
    Offset M3 CAB's (either stock or Powerflex)
    Front and Rear Sways (Suspension Techniques Kit from Turner which includes Adjustable Rear Links, Poly Bushings )
    Front Strut Brace (from IE)
    Tie Rods (Stock)
    Front Strut Mounts (???)
    Heavy Duty Rear Shock Mounts
    RTAB's
    Diff Mount
    Subframe Bushings

    The Bilstein Sports, H&R Sports, IE Fixed Camber Plates, and Wheel Bearings were purchased used off of a local CCA member. Everything else I am planning on purchasing in the next few weeks. Do I need the Front Strut Mounts with the used Billy/H&R's that I already have (the complete front strut housing is what I already have).

    I also havent decided if I am going to go with Lemfoerder Control Arms with stock M3 CAB's from Turner, or Meyle Control Arms with Powerflex Bushings which are on sale at -->
    http://store.bimmerworld.com/shared...2=634147286&CategoryID=22&Target=products.asp

    Is there anything else I should be getting? Any other comments/concerns?

    If I were to go with poly bushings in the rear, I would get the 70A Subframe Bushings from AKG Motorsport. The problem with that though is that I have read that you should use the same material for both subframe and diff mounts, thus if I were to use the poly Subframe Bushings I would also get the AKG poly diff mount, which is 75D in durometer. That seems too hard for me, as it would transmit too much NVH. The problem is I cannot find a softer poly diff mount.

    The same thing with the RTAB's. AKG's are only available in 75D, which again I would think is way too hard. I guess there is always the option of going with Powerflex RTAB's, but it does not say what durometer they are --> http://store.bimmerworld.com/shared...2=520148873&CategoryID=35&Target=products.asp

    Up until last night I had been leaning towards poly bushings everywhere. Now Im thinking it may be better to go stock, and simply upgrade later on if I feel its necessary.

    One last thing: Unfortunately I wont be able to do all of this work by myself. Any comments on finding someone to do the work for me? How much is this going to run me to have it installed? Im not expecting a low number. I would do it myself (or actually with a more knowledgable friend helping me), but every bolt I have ever tried to loosen on my car has been impossible to get off due to its age.

    Thanks for the replies guys. This forum is turning out to be a great place to hang out. It seems much better than the old message board on the old CCA website.
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    mooseheadm5

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    Where are you located? The bill for replacing all of this stuff is going to be very high. I would try to group certain things together to save labor times if I were you.

    Grinch337 guest

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    Im in Northern Jersey. I am planning on shopping around heavily before choosing who is going to do the work. Apparently the guy who runs E30Tech.com does work on E30's, and he is local to me. http://www.e30tech.com/forum/showthread.php?t=48979

    So I plan on emailing him, as Im sure he'll be the best price. Any other suggestions? How much am I actually looking at? Should I hold off on having some things installed, such as swaybars, because once the main work is done I will be able to do them myself?
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    mooseheadm5

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    I don't know your level of skill, so it would be hard to say what you are capable of doing. Significant duplicate labor would occur with front struts/mounts/camber plates. You can do the control arms and bushings at the same time, as well as tie rods to save a little (very little.) You should do bushings and control arms at the same time. Either the Meyle or Lemforder arms will be fine, but you don't have to replace yours unless they are bad. Even then, if it is just the outer ball joint that is bad you can have a new one pressed in so long as the guy knows the trick to getting the arm off without damaging the inner joint boot. Only do wheel bearings if they are bad. There is only duplicate labor if you are doing brakes on the front. The rears should really only be done if the guy has a bearing puller and even then only if they are bad. Of course if you are pulling the trailing arms to do the bushings, then you can go ahead and do the bearings. I personally would not do RTABs unless they are bad because of the labor involved. Rear subframe bushings should only be done by a shop with the special tool, or else you will have to have the rear subframe pulled from the car at significant cost (someone I know was quoted around 8 hours at the dealer, I charge 3 hours for the pair with the tool.) If you do none of the work yourself, you are looking at $1500-$3000 of dollars in labor depending on what they guy charges per hour, how you group the jobs together, and whether or not he charges you more because you are bringing your own parts.
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    mooseheadm5

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    And timing belt is 60k or 4 years (some say 5.) Do it or risk turning your car into a parts car. I have purchased numerous E30s for less than $200 because of snapped timing belts.

    Grinch337 guest

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    Thanks for your advice Paul. $1500-3000 is more than I was expecting. Let me spell out what exactly I think I need done. Please correct me where I am wrong. I am more or less a novice when it comes to working on cars. I am mechanically inclined, but just don't have a lot of experience in wrenching stuff myself. At the very least I need someone to help me that knows what they are doing. I am planning on doing all of the above in one shot, therefore hopefully minimizing duplicate work.

    The used Bilsteins, H&Rs, IE Fixed Camber Plates and wheel bearings are already put together. When I purchased them (remember they are used) I literally just detached the entire front strut housing from the donor car, and its now sitting in my basement. Thus, I believe that I just need to have the front strut housing that is on my car now removed, and then insert the struts/spring combo that is already put together. I of course am going to have to move the brakes which were replaced recently to the new struts.

    While the existing front strut housing is off of the car, the new tie rods and new control arms/cab's will be put on the car. I am probably going to have the bushings pressed on to the control arms at the place that I buy them from (either Turner or Bimmerworld).

    The following question shows my ignorance level --> do the front strut mounts go within the front strut housing/assembly, meaning that they are already in the strut housings that I am already in possession of?

    At this point, if I am correct in my thinking, it makes the most sense to switch the sway bar to the new one. No matter what I can do the front strut bar myself. That takes care of the front.

    As to the rear, thanks for the advice on the Subframe Bushings. I knew that it was pretty complicated, and will definitely have a shop do it. It therefore makes sense to have the shop do the diff mounts at the same time as well, correct?

    I dont know about the RTABs. Like I said, the car is on the originals with 151k on them. The rear end doesnt feel solid at all. How would I know whether RTAB's are bad? If changing them is a real pain in the butt, maybe I'll leave them be for now. However, Im more inclined to the job once and do it right.

    As for the timing belt, this summer will be the 4 year mark. The car has only seen about 12k miles since it was done. I will be doing it soon, thats for sure. Maybe it makes sense to do it now, as I may be able to get a discount on labor if the shop also has to do the timing belt.
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    mooseheadm5

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    That will be much cheaper, then. You simply bolt that whole assembly up to the car after removing the old stuff and doing the tie rods and control arms

    Does that mean you will have to buy new lollipops as well? May not be worth the extra money. I'd consult the tech doing the work.

    The struts are in there, so it is a bolt up operation. If there is a spring on the assembly, then the upper strut mount is already in place. If not, then it will have to be purchased/assembled. How about a pic of what you got?

    There are only 4 (ir was it 6?) bolts that hold the sway bar on the car and two of them must be removed to remove the control arms. It is not much more work to toss on the sway bar at that time. The upper strut brace is held on by three nuts on each side which must come off to replace the struts, so it would be up to you to decide if it is worth it to have the tech toss the strut brace on while he is there.

    Maybe. If they can only do the subframe mounts by pulling the subframe, then they must remove the drive axles, diff, and lots of other crap. It would make sense to put in the diff mount (there is only one.) This could, BTW, lead to you needing to replace a portion of brake line, as the T fitting at the back is often rusted up pretty badly. Otherwise, replacing the diffmount only requires removing the rear cover and pressing in a new one. I advise finding a tech with the special tool

    The tech will eb able to show you if they are bad.

    Do the timing belt as required. You will not get a discount on labor.

    Grinch337 guest

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    So I've been thinking about this all day, and after writing out the specifics about the labor involved I think Im ready to tackle the front parts by myself with the help of a more knowledgable friend. If worse comes to worst, I'll ask a fellow local CCA member to help. Even though most of the bolts have been in place for 20 years, I think that if I can use air tools and a large breaker bar we'll be able to replace the front parts, which will save me a significant amount of money. The rear I am going to have a tech do.

    I am going to take a pic, but I wont be able to post it until this weekend. After reading what you have written, I think the front strut housings that I have already have the front strut mounts in them.

    As for the rear, I have looked closer at the Powerflex bushings (all of them: RTAB's, Subframe Bushings, and the Diff Mount), and I think Im ready to deal with the excess NVH on the street to have a stiffer car that I will enjoy more for several more years on the track. Bimmerworld suggests that they are ok for hard core street use. My commute is short, so even though it is on rough roads I think it will be ok for the year that my E30 will serve as a DD.

    The excess cost of buying Powerflex Bushings will be offset by performing the work on the front by myself. I also want to do the RTAB's because like I said, I would rather do the job once and do it the right way.

    My last question: Bimmerworld charges $75 for pressing the CAB into new carrier housings. I know I dont need to buy new carrier housings (and I can even get an extra set for free beforehand so there is less downtime), but can I take my new CA, CAB's, and lollipops to any local mechanic to have the bushings pressed in? How much does this typically cost?

    Any other comments? I would rather pay a little extra to have quality work done with piece of mind, but of course I would always like to have a few extra dollars in my pocket.

    Thanks for all of the responses. Paul: I've enjoyed reading your responses to Botond. You are a real asset to this forum. Thanks for the hard work and your time.
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    mooseheadm5

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    Any machine shop or mechanic ought to press in CABs for the price of a 6 pack after hours. It literally takes 5 minutes for a pair. Clay is really pushing it asking $75 for that service unless he goves you new lollis with it. You will also need to press them onto the control arms, but I have heard that some have luck with spray silicone lube and a well placed whack with a deep well socket and a BFH. I believe that it is possible for most mechanically inclined people to change out entire steering knuckles and control arms on E30s, just be smart and safe. If you do tie rods (outer or whole assemblies?) you will need to have it aligned, but then you probably will want to do that anyway (assuming you want the offset M3 CABs.) Buy a Bentley manual- NOW! Do the front first and the rear struts and springs and both sway bars (very easy, though the rear bar needs to be threaded in just right) then drive it for a week or so before commiting to more NVH harshness. My brother had this attitude with his E28 M5 (he and his buddies own Road Race Technologies now) and changed his mind after hearing the diff in his teeth when he drove. He also had the needle bearing UUC shifter and could feel the synchros in his wrist with every shift. He changed his mind and sucked it up and built a separate track car. As I said before, there is no duplicate labor between RTABs and cross member bushings if the shop has the special tool for the cross member bushings, which are the most likely cause of the less than planted feeling in the rear. I'd wait on the RTABs if money is a concern. You can always do most of the work yourself later once you get into it.
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    MGarrison

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    Couple other thoughts to add - when or if you drop the rear subframe/trailing arms/differential, that's the time to closely assess the solid brake lines running to the rear of the car. They'll never be easier to replace than when the subframe is out, if they're rusted, bubbled, or showing obvious deterioration and need replacement.

    I have had just the solid rubber rear diff mount in my 325is for many years of track use, and it's held up just fine. My original stock rear subframe bushings held up quite well for a very long time. I only replaced them w/ Ireland Engineering ones when the rear subframe had to come out to resolve another issue (cracked rear trailing arm mounting tab) and the replacement bushings for the originals hadn't been installed far enough to get fully seated in the subframe. Point being, the stock ones will hold up reasonably well for a long time for a mix of driver's schools and street driving; however, the urethane ones should last even that much longer.

    I have K-mac offset rear trailing arm bushings. Again, the stock items here will hold up pretty well for a good long while, but if you have to get into that area for anything, there's little downside to upgrading those, and you gain some adjustability that could only otherwise be gained by slotting the trailing arm mounting tabs. One downside to adjustable rear trailing arm bushings is - they can loosen up! If you get those, once you get the car aligned, it's a good idea to retorque them a couple times a year (use a torque wrench) to make sure they stay tight. (unexpected rear-wheel steering and shifting is a really disconcerting feeling....)

    This discussion reminded me about the trailing arm mounting tabs. They are affixed with either a couple of spot welds, or are only welded on one side. If you drop the subframe, it's not a bad idea to beef up the tab mountings with reinforcing welds. Took me about 1.5-2 years to accurately diagnose that problem, and not discovered until the 2nd time the rear subframe was pulled. And that was after trying a whole slew of other stuff.

    I have an Autosolutions short shift kit, with which I've been completely happy. Don't forget a short shift kit for a track car - very nice improvement.

    The offset strut mounts are good for 1/2º of neg. camber, the camber plates should get you a lot more than that - I wouldn't say it would be worth the expense or time of disassembling the strut assemblies for the extra 1/2º from the offset mounts until you got to the point where the strut mounts you already have need replacing.

    ditto on Kudo's to Paul - your willingness to share your expertise & experience is definitely an invaluable and much appreciated asset around here.
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    mooseheadm5

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    BTW, adjustible RTABs require professional setup work, and offset ones need to be installed right the first time. If you have a really beefy rear sway bar you should also reinforce the mounts at the trailing arms.
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    mooseheadm5

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    You order all that stuff yet? Just found this in ebay:

    click

    Grinch337 guest

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    Thanks for the link. I can't tell if the parts are OEM parts, or aftermarket parts which may or may not be "built to exceed OE specifications." I emailed them to ask. If they are not OEM parts, I would hesitate before buying the kit. I would prefer to spend more on parts I am sure are quality parts rather than cheap crap from China. What do you think about it?

    I am planning on responding to some of the above posts tonight when I have more time. I have a few questions, and I took some pics of my front strut housings. I will post them tonight.

    Grinch337 guest

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    Received a response from Deutsche Parts (the company selling the parts on Ebay). They said:

    "The parts are Manufactured by Hamburg Technic in Germany."

    and thats all. Im going to do some research on Hamburg Technic.

    Grinch337 guest

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    When googling "Hamburg Technic," this is the second link (the first being the manufacturers webpage):
    http://www.bimmerfest.com/forums/showthread.php?t=239444
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    mooseheadm5

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    There you have it. Go for Meyle, then. I don't like TRW joints. I was pissed at Meyle for a while, but their quality has really jumped up several notches in the last couple of years.

    Grinch337 guest

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    Ok, here are the pics of what I have.

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    So Ive recruited my buddy/CCA member to help me with this project. He has access to air tools. Hes been wrenching on BMW's for years, so I am pretty confident we can do this. I havent ordered the parts yet, so its going to be a month or so until we can actually tackle this project.

    Im going to take the bushings to a local mechanic before we do it. Well be able to get them on the CA's with a mallet I think.

    So it looks like I have tie rods on already on the front strut assemblies that I have. Why did the previous user put plastic baggies on the ends before covering it with the plastic sleeve? Should I replace these tie rods now, or give them a shot?

    I was planning on an alignment. I will be able to get the car aligned enough at my buddy's place to drive it directly to a shop to perform the alignment, correct?

    Already have one.

    As you suggest, Im going to hold off on the RTAB's for now. Since there is little duplicate work involved I am just going to have the tech check them when I have the Subframe Bushing and Diff Mount installed. I will also have him check out the brake lines at this point.

    What else do I need to know about the front strut housings that are already in my possession. What can I use to clean the surface rust on them before installing, or should not worry about it? Is that a rear shock mount on the top of the rear struts? If it is, should I replace them?

    Im planning on putting a 22mm bar on the front and a 19 on the back, with new poly bushings and adjustable links. Should I be alright with the stock mounts?

    What else do I need to know.

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