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Thread: M suspension swap

  1. #1
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    Question M suspension swap

    I have a 93 325i, my suspension has seen better days. Would it be worth it to upgrade to M3 subframes, control arms, spindles and sway mounts? I plan to install either GC or H&R coil-overs, and replace all bushings at the same time. Anyone done this? What kinds of problems do you think I'll be inflicting upon myself by swaping in M components? What the heck will this cost me?!
    thanx.
    jorge

  2. #2
    Join Date
    Mar 2001
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    1996 M3 lux, 1988 325
    Subframe, no
    rear control arms, no
    front control arms, yes
    swaybar end links, yes - requires different or modified struts
    spindles/kingpin, only if doing a brake upgrade.
    == Stable mates ==
    -1996 M3 Lux, bright red (hellrot), Modena interior. Aus Freude Am Fahren!

    -1988 325, Alpenweiss. The commuter.
    BMW HOWTOs

  3. #3
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    My Cars
    93 332is Turbo
    I swapped just the springs/shocks and it helped tons, but now I am swapping the control arms too.
    stock is the new mod

  4. #4
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    E30M3,318is,318i,E21320
    not necessary,

    Just get M3 front control bushes and strut mounts(only geometry difference between M and Non M cars), then run with what ever shock/spring combo you want. When deciding on struts choose M3 or not depending if you want to change to M3 front swaybar links, then make your own links out of spherical bearing ends. This combo will put you over stock M3 handling.

    Subframe, no difference
    rear control arms, junk, their all stamped sheet metal
    front control arms, yes....oh boy bigger ball joints
    swaybar end links, yes

    more option suggestions
    rear control arms, BMP, TC Kline, AA all make solid arms
    X-brace would compliment everything else
    maybe use Powerflex bushes and your set

  5. #5
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    Hold on a sec...

    Could you please simplify what needs changing, just explain in list form..i.e

    1. change bla bla bla
    2. change bla ..

    I've been thinking about this for ages, also if all this was done would it enable you to put wider tyres on ?, my 318is is not built for speed but for looks, I'd love to put 255's on the rear!!

  6. #6
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    ok here it goes

    1. change front control arm bushes to M3 ones. there is two different bushes; ones made for the 95 M5 (offset bushes) ones made 96+ (center hole bushes) the offset ones will give additional castor to lessen bump steer and tramline with bigger tires

    2. buy M3 front upper strut mounts. again two different versions; in 95 center position additional camber or 96+ rear position additional castor and additional camber

    you could stop here since this give you M3 geometry except sway end links or

    3. buy new struts/springs for M3 ie. bilsteins etc, etc.
    4. buy new M3 sway links to work with your new M3 struts

    you could stop here or go even further

    5. buy M3 front control arms (they have bigger ball joints)
    6. buy aftermarket rear control arms (stock are stamped sheet metal and don't offer much camber adjustment)

    7. buy an X-brace to finish it off (this will compliment your suspension even at the stock level)

    Important:
    8. buy rear trailarm bushes (or toe bushes as their sometimes referred to) buy only 96+ M3 version toe bushing since their harder and deal better with harder suspension OR buy Powerflex bushes which I highly recommend.

    You can run the staggered tire setup if you like the look, but for handling I don't recommend it. I would use 17x8 at all fours with 235/40/17 rubber.

  7. #7
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    Just an fyi, on caster:

    http://www.ground-control.com/gctalk5.htm

    In this regard, my understanding is that with the 96+ M3's, BMW migrated to a concentric front control arm bushing, but still got lots of caster b/c of a change in geometry in the front control arms from the 95's.

    I believe that 96+ M3 front control arms with eccentric bushings will give you too much caster.

    Jeff
    In the slow lane

  8. #8
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    Definately be careful mixing 95, and 96-on M3 front suspension parts. While they all fit together, they don't necessarily give you the geometry you are looking for.

    On the 95 M3, the only major geometry change was to increase the caster. This was done by using offset bushings on the back of the control arm, and an upper strut bearing that moves the top of the strut toward the rear of the car. Increased caster should give you greater straight-line stability (i.e. less "tramlining"). It does little to change any bump steer, which the E36 does not do anyway. The nice thing is the control arm, and kingpin geometry is the same for a 95M3 as a regular E36. In 96, the control arms, kingpins, bushings, and strut bearings all changed. For example, if you put a 96 strut bearing on a regular E36, you will get about 1/2 to 1 degree of *positive* camber. Your safest bet unless you change *everything* on the front to 96M3, is to stick with the 95 parts.

    Now with that out of the way, here is a link to my post that lists the parts that I changed when I went to M3 specs.

    http://bimmerforums.com/forum/showth...&threadid=3476

    I still have to fix the links to the pictures, but the text is there.

    Have fun!
    Bernman

  9. #9
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    Outstanding thread! The timing is perfect!

    I want to reduce the tramlining on my lowered '95 318is.

    So to reiterate what you're saying (making sure I'm on the right theory page:
    - Installing the '95 M3 upper strut bearing and '95 M3 offset control arm bushings will give me the desired caster adjustment with no camber change.

    Way cool... but now to exercise our minds...
    But I would ALSO love to undo some of the negative camber induced by the lowering to preserve tires....

    So does anyone know if can I do what you just advised against - mix parts from differing years. Specifically, can I use the '96 M3 upper strut bearing and '95 M3 control arm bushings to get the caster increase AND reduce the negative camber?

    It seems like it would if the 96 strut bearing just moves the top end of the strut outward while leaving it the same offset rearward... Maybe have to ovalize one of the lower strut mount holes to allow the strut to tilt outward with the stock '95 318is control arm...

    I truly appreciate any advice or shared experiences!

  10. #10
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    The front camber does not change very much when lowering an E36. Have you had yours checked? The rear does change when you lower, but there is adjustment for that.

    Anyway, if you really do want to reduce the camber in the front, you can use the 96 M3 strut bearing. That will move the top of the strut back, and toward the outside, giving you increased caster, and reduced camber. In my case, the alignment tech had to increase the caster by installing washers between the strut and the kingpin. I have the cup kit, and 96M3 strut bearings. The Camber is set at 1 degree negative.

  11. #11
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    Oops, forgot to attach the image...

    You can see how the center of the bearing is moved toward the outside of the car on my strut bearing. On the 95M3, the bearing lines up right in the middle, but is still toward the back of the car.
    Last edited by Bernman; 04-12-2002 at 07:55 PM.

  12. #12
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    Excellent! Thank you, Bernman. And the photo was quite helpful, too.

    I didn't measure how much camber was induced, but I could visually see they were tilted. I placed my framing square on the floor and there definitely was some camber - I did a 1.75" drop. Now that I know I might be able to "fix it", I will do some more accurate measuring. If it is more than 1.5 degrees, I will use the '96 bearing.

    Thanks again! :

  13. #13
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    Originally posted by frayed
    Just an fyi, on caster:

    http://www.ground-control.com/gctalk5.htm

    In this regard, my understanding is that with the 96+ M3's, BMW migrated to a concentric front control arm bushing, but still got lots of caster b/c of a change in geometry in the front control arms from the 95's.

    I believe that 96+ M3 front control arms with eccentric bushings will give you too much caster.

    Jeff
    speaking of caster, I had this talk with every tuner that sells replacements and they all say and sell the same thing

    Even for the 96+ M3 models they only offer a spherical bearing or delrin, urethane replacements in OFFSET which means more caster like the 95 M3 bushing.....they all said to increase caster for more straight line stability and are putting these on all 96+ M cars.

    So what I'm getting at is their all saying it doesn't matter. Well I'll be able to tell you soon. I'm going to install new 95 M3 offset bushes with my 96 M3 upper strut mounts in two weeks. This is on a modded 96' 328is:

    My center hole urethane bushes(5 months old) are total garbage right now so I'll do a little experimenting since no one has a clear answer.

  14. #14
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    Excellent! I'll be eagerly awaiting your results! And if it's not too much bother, can you report how much the camber changes?

    Do you know if your '96 328is used the same front control arm geometry as the '96 M3, or will it be identical to the '95?

    Last sponge request: Where are/did you get the strut mounts and bushings from? Good pricing?

  15. #15
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    Right now I have the exact geometry as a 96' M3 on the alignment rack.

    96' 328 control arms
    96' M3 center control bushes
    96' M3 strut mounts
    Bilstein sport struts
    O.E. sport H&R springs

    I ordered all my stuff from BMP Design. For stock parts I usually use bimmerparts, but I'm starting to use my local dealer. I get a special discount on dealer parts now.

  16. #16
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    Good morning, autox320!
    I just returned from a 2 week trip and was wondering if you have had a chance to complete the '96 strut bearing/'95 offset bushings swap?
    Results?
    Thanks!

  17. #17
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    Just to put some clarification (and correction?) to some of what I've read so far:

    1. change front control arm bushes to M3 ones. there is two different bushes; ones made for the 95 M5 (offset bushes) ones made 96+ (center hole bushes) the offset ones will give additional castor to lessen bump steer and tramline with bigger tires
    The offset bushings push the rear of the control arm out, increasing caster and also the wheelbase (by about 10 mm). The 96 bushings are centered, but the control arm itself is angled differently to produce the forward shift of the wheel and the increased caster (in combination with the strut mount).

    2. buy M3 front upper strut mounts. again two different versions; in 95 center position additional camber or 96+ rear position additional castor and additional camber
    The "additional camber" is actually less negative = closer to zero camber.

    5. buy M3 front control arms (they have bigger ball joints)
    As mentioned above, there are two E36 front control arms.

    In 96, the control arms, kingpins, bushings, and strut bearings all changed. For example, if you put a 96 strut bearing on a regular E36, you will get about 1/2 to 1 degree of *positive* camber. Your safest bet unless you change *everything* on the front to 96M3, is to stick with the 95 parts.
    You may not necessarily end up with positive camber, but your camber would certainly be less negative/more positive than before.

    Judging from the alignment readouts of some people, I believe that the spindle/stub axle on the 96+ M3 may be at different angle, perhaps offsetting the camber change from the strut mounts. In terms of suspension kinematics, there are different roll center effects when you add camber at the strut mount vs. at the stub axle.

  18. #18
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    bump...

    Autox320 - Any conclusions yet? I am ordering strut mounts now, and curious if you want to tell me NOT to go with the '96's.

    Thanks!!!

  19. #19
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    Jorge-

    I am doing a suspension swap as well. I did an M3 suspension conversion on my car (just swapped it back to the sport package and sold it for my new suspension) Here is a thread from this board that you might find helpful

    http://www.bimmerforums.com/forum/sh...threadid=30940

    Here is what I have decided to do with my suspension swap:

    -Bilstein PSS9 coilover
    -UUC Strut Barbarian (front strut brace)
    -Replacing control arms
    -Upgrading to Powerflex suspension bushings
    -H&R 5mm front spacers (since I am running my stock sport package rims for now)
    -E46 M3 Rear shock mounts (stronger RSMs are a must if you are putting in stiffer shocks)
    -Z3 reinforcement plates

    Already have the X-Brace and retaining the sport package sway bars for now.

    My friend just had his PSS9 installed on his 323is and it rides like a dream-NOT rough at all! My sport suspension feels harsher and its not even the M. And it handles great!

    Go to my site for a breakdown between component differences between the 325 and 95 M3:

    http://www.geocities.com/my325is/M3vs325is.html

    If you decide to go with an straight M3 suspension conversion go to this page for the parts you'll need:

    http://www.geocities.com/my325is/m3suspension.html

    If you have the money, go with a coilover and upgrades and you can have a car that'll handle better than a stock M3.

    Good luck!!!
    Last edited by Jed; 05-31-2002 at 12:16 PM.
    What would Crockett and Tubbs do?

    1994 E36 Hellrot/Black 325is
    2007 E92 Jet Black/Saddle Brown 335i

  20. #20
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    Jorge, the suspension setup you are proposing is very similar to mine. I have installation pictures, comments and analyses on my webpage if you are interested.

  21. #21
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    thanks to everyone who responded to this thread. I appreciate it as a reader.

    Thanks for the picture Bernman, you've got a PM by the way.

  22. #22
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    hey guys

    Everything in my life has been put on hold at the moment. I autocross a 83' 320is. Well during working on this car on April 29 it fell off the jack with my left arm caught in between the rear fender well and tire. Story short I almost lost my arm, but came out with just a severe crush injury to my forearm muscle severing all except the bone. I'm in therapy now and have had little time for the cars. Right now I just want to get back to being able to drive a car on the street so my wife doesn't have to take her time driving me to work everyday.

  23. #23
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    That is awful man. I really feel for you

    I hope you are doing well (or as well as can be expected) and will be able to drive again soon.

    You will be in my thoughts...

    Bernman

  24. #24
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    I'm equally distraught to hear this. I truly hope it is healing well and you regain full usage.

    This story will stay with me, and I will think of you every time I jack the car, and will now double check the stands.

    I have the '96 upper strut bearings on the way. My sister was vacationing in Europe and picked some up in Hamburg while getting parts for her 528 headlights. Would you believe $52 apiece over there?

    I'll eventually install. I want to do the eccentric bushings at the same time and am currently short on cash (all $$ going to gasoline to drive to sailboat races). If it overcorrects the camber too far, it will be easy to relocate the plate inward. Or at least easier than moving a centered ('95) plate outward. I'll let all know what I find.

  25. #25
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    AutoX320, I hope you recover fully. It's good to hear that your arm is still attatched!

    Everybody, it can't be stressed enough how important it is to always follow saftey precautions when working on a car. Sturdy jack stands, eye protection, gloves when needed, latex/nitrile gloves for almost every other procedure.

    Even if you never had any sort of incident while working on a car, don't think that it will never happen. I have *almost* had a car slip off a jackstand while raising the other side of the car. I have had a car fall off a jack. Fortunately in neither of those occurences was I under the car.

    Be carefull and don't rush.
    == Stable mates ==
    -1996 M3 Lux, bright red (hellrot), Modena interior. Aus Freude Am Fahren!

    -1988 325, Alpenweiss. The commuter.
    BMW HOWTOs

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